\input texinfo          @c -*-texinfo-*-
@c %**start of header
@setfilename gettext.info
@settitle GNU @code{gettext} utilities
@finalout
@c %**end of header

@include version.texi

@dircategory GNU Gettext Utilities
@direntry
* Gettext: (gettext).                           GNU gettext utilities.
* gettextize: (gettext)gettextize Invocation.   Prepare a package for gettext.
* msgfmt: (gettext)msgfmt Invocation.           Make MO files out of PO files.
* msgmerge: (gettext)msgmerge Invocation.       Update two PO files into one.
* xgettext: (gettext)xgettext Invocation.       Extract strings into a PO file.
@end direntry

@ifinfo
This file provides documentation for GNU @code{gettext} utilities.
It also serves as a reference for the free Translation Project.

Copyright (C) 1995, 1996, 1997, 1998, 2001 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.
@end ifinfo

@titlepage
@title GNU gettext tools, version @value{VERSION}
@subtitle Native Language Support Library and Tools
@subtitle Edition @value{EDITION}, @value{UPDATED}
@author Ulrich Drepper
@author Jim Meyering
@author Fran@,{c}ois Pinard

@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1995, 1996, 1997, 1998, 2001 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.
@end titlepage

@ifinfo
@node Top, Introduction, (dir), (dir)
@top GNU @code{gettext} utilities

@menu
* Introduction::                Introduction
* Basics::                      PO Files and PO Mode Basics
* Sources::                     Preparing Program Sources
* Template::                    Making the PO Template File
* Creating::                    Creating a New PO File
* Updating::                    Updating Existing PO Files
* Binaries::                    Producing Binary MO Files
* Users::                       The User's View
* Programmers::                 The Programmer's View
* Translators::                 The Translator's View
* Maintainers::                 The Maintainer's View
* Conclusion::                  Concluding Remarks

* Language Codes::              ISO 639 language codes
* Country Codes::               ISO 3166 country codes

@detailmenu
 --- The Detailed Node Listing ---

Introduction

* Why::                         The Purpose of GNU @code{gettext}
* Concepts::                    I18n, L10n, and Such
* Aspects::                     Aspects in Native Language Support
* Files::                       Files Conveying Translations
* Overview::                    Overview of GNU @code{gettext}

PO Files and PO Mode Basics

* Installation::                Completing GNU @code{gettext} Installation
* PO Files::                    The Format of PO Files
* Main PO Commands::            Main Commands
* Entry Positioning::           Entry Positioning
* Normalizing::                 Normalizing Strings in Entries

Preparing Program Sources

* Triggering::                  Triggering @code{gettext} Operations
* Mark Keywords::               How Marks Appear in Sources
* Marking::                     Marking Translatable Strings
* c-format::                    Telling something about the following string
* Special cases::               Special Cases of Translatable Strings

Making the PO Template File

* xgettext Invocation::         Invoking the @code{xgettext} Program

Updating Existing PO Files

* msgmerge Invocation::         Invoking the @code{msgmerge} Program
* Translated Entries::          Translated Entries
* Fuzzy Entries::               Fuzzy Entries
* Untranslated Entries::        Untranslated Entries
* Obsolete Entries::            Obsolete Entries
* Modifying Translations::      Modifying Translations
* Modifying Comments::          Modifying Comments
* Subedit::                     Mode for Editing Translations
* C Sources Context::           C Sources Context
* Auxiliary::                   Consulting Auxiliary PO Files
* Compendium::                  Using Translation Compendiums

Producing Binary MO Files

* msgfmt Invocation::           Invoking the @code{msgfmt} Program
* MO Files::                    The Format of GNU MO Files

The User's View

* Matrix::                      The Current @file{ABOUT-NLS} Matrix
* Installers::                  Magic for Installers
* End Users::                   Magic for End Users

The Programmer's View

* catgets::                     About @code{catgets}
* gettext::                     About @code{gettext}
* Comparison::                  Comparing the two interfaces
* Using libintl.a::             Using libintl.a in own programs
* gettext grok::                Being a @code{gettext} grok
* Temp Programmers::            Temporary Notes for the Programmers Chapter

About @code{catgets}

* Interface to catgets::        The interface
* Problems with catgets::       Problems with the @code{catgets} interface?!

About @code{gettext}

* Interface to gettext::        The interface
* Ambiguities::                 Solving ambiguities
* Locating Catalogs::           Locating message catalog files
* Charset conversion::          How to request conversion to Unicode
* Plural forms::                Additional functions for handling plurals
* GUI program problems::        Another technique for solving ambiguities
* Optimized gettext::           Optimization of the *gettext functions

Temporary Notes for the Programmers Chapter

* Temp Implementations::        Temporary - Two Possible Implementations
* Temp catgets::                Temporary - About @code{catgets}
* Temp WSI::                    Temporary - Why a single implementation
* Temp Notes::                  Temporary - Notes

The Translator's View

* Trans Intro 0::               Introduction 0
* Trans Intro 1::               Introduction 1
* Discussions::                 Discussions
* Organization::                Organization
* Information Flow::            Information Flow

Organization

* Central Coordination::        Central Coordination
* National Teams::              National Teams
* Mailing Lists::               Mailing Lists

National Teams

* Sub-Cultures::                Sub-Cultures
* Organizational Ideas::        Organizational Ideas

The Maintainer's View

* Flat and Non-Flat::           Flat or Non-Flat Directory Structures
* Prerequisites::               Prerequisite Works
* gettextize Invocation::       Invoking the @code{gettextize} Program
* Adjusting Files::             Files You Must Create or Alter

Files You Must Create or Alter

* po/POTFILES.in::              @file{POTFILES.in} in @file{po/}
* configure.in::                @file{configure.in} at top level
* config.guess::                @file{config.guess}, @file{config.sub} at top level
* aclocal::                     @file{aclocal.m4} at top level
* acconfig::                    @file{acconfig.h} at top level
* Makefile::                    @file{Makefile.in} at top level
* src/Makefile::                @file{Makefile.in} in @file{src/}

Concluding Remarks

* History::                     History of GNU @code{gettext}
* References::                  Related Readings

@end detailmenu
@end menu

@end ifinfo

@node Introduction, Basics, Top, Top
@chapter Introduction

@quotation
This manual is still in @emph{DRAFT} state.  Some sections are still
empty, or almost.  We keep merging material from other sources
(essentially e-mail folders) while the proper integration of this
material is delayed.
@end quotation

In this manual, we use @emph{he} when speaking of the programmer or
maintainer, @emph{she} when speaking of the translator, and @emph{they}
when speaking of the installers or end users of the translated program.
This is only a convenience for clarifying the documentation.  It is
@emph{absolutely} not meant to imply that some roles are more appropriate
to males or females.  Besides, as you might guess, GNU @code{gettext}
is meant to be useful for people using computers, whatever their sex,
race, religion or nationality!

This chapter explains the goals sought in the creation
of GNU @code{gettext} and the free Translation Project.
Then, it explains a few broad concepts around
Native Language Support, and positions message translation with regard
to other aspects of national and cultural variance, as they apply to
to programs.  It also surveys those files used to convey the
translations.  It explains how the various tools interact in the
initial generation of these files, and later, how the maintenance
cycle should usually operate.

Please send suggestions and corrections to:

@example
@group
@r{Internet address:}
    bug-gnu-utils@@gnu.org
@end group
@end example

@noindent
Please include the manual's edition number and update date in your messages.

@menu
* Why::                         The Purpose of GNU @code{gettext}
* Concepts::                    I18n, L10n, and Such
* Aspects::                     Aspects in Native Language Support
* Files::                       Files Conveying Translations
* Overview::                    Overview of GNU @code{gettext}
@end menu

@node Why, Concepts, Introduction, Introduction
@section The Purpose of GNU @code{gettext}

Usually, programs are written and documented in English, and use
English at execution time to interact with users.  This is true
not only of GNU software, but also of a great deal of commercial
and free software.  Using a common language is quite handy for
communication between developers, maintainers and users from all
countries.  On the other hand, most people are less comfortable with
English than with their own native language, and would prefer to
use their mother tongue for day to day's work, as far as possible.
Many would simply @emph{love} to see their computer screen showing
a lot less of English, and far more of their own language.

However, to many people, this dream might appear so far fetched that
they may believe it is not even worth spending time thinking about
it.  They have no confidence at all that the dream might ever
become true.  Yet some have not lost hope, and have organized themselves.
The Translation Project is a formalization of this hope into a
workable structure, which has a good chance to get all of us nearer
the achievement of a truly multi-lingual set of programs.

GNU @code{gettext} is an important step for the Translation Project,
as it is an asset on which we may build many other steps.  This package
offers to programmers, translators and even users, a well integrated
set of tools and documentation.  Specifically, the GNU @code{gettext}
utilities are a set of tools that provides a framework within which
other free packages may produce multi-lingual messages.  These tools
include

@itemize @bullet
@item
A set of conventions about how programs should be written to support
message catalogs.

@item
A directory and file naming organization for the message catalogs
themselves.

@item
A runtime library supporting the retrieval of translated messages.

@item
A few stand-alone programs to massage in various ways the sets of
translatable strings, or already translated strings.

@item
A special mode for Emacs@footnote{In this manual, all mentions of Emacs
refers to either GNU Emacs or to XEmacs, which people sometimes call FSF
Emacs and Lucid Emacs, respectively.} which helps preparing these sets
and bringing them up to date.
@end itemize

GNU @code{gettext} is designed to minimize the impact of
internationalization on program sources, keeping this impact as small
and hardly noticeable as possible.  Internationalization has better
chances of succeeding if it is very light weighted, or at least,
appear to be so, when looking at program sources.

The Translation Project also uses the GNU @code{gettext} distribution
as a vehicle for documenting its structure and methods.  This goes
beyond the strict technicalities of documenting the GNU @code{gettext}
proper.  By so doing, translators will find in a single place, as
far as possible, all they need to know for properly doing their
translating work.  Also, this supplemental documentation might also
help programmers, and even curious users, in understanding how GNU
@code{gettext} is related to the remainder of the Translation
Project, and consequently, have a glimpse at the @emph{big picture}.

@node Concepts, Aspects, Why, Introduction
@section I18n, L10n, and Such

Two long words appear all the time when we discuss support of native
language in programs, and these words have a precise meaning, worth
being explained here, once and for all in this document.  The words are
@emph{internationalization} and @emph{localization}.  Many people,
tired of writing these long words over and over again, took the
habit of writing @dfn{i18n} and @dfn{l10n} instead, quoting the first
and last letter of each word, and replacing the run of intermediate
letters by a number merely telling how many such letters there are.
But in this manual, in the sake of clarity, we will patiently write
the names in full, each time@dots{}

By @dfn{internationalization}, one refers to the operation by which a
program, or a set of programs turned into a package, is made aware of and
able to support multiple languages.  This is a generalization process,
by which the programs are untied from calling only English strings or
other English specific habits, and connected to generic ways of doing
the same, instead.  Program developers may use various techniques to
internationalize their programs.  Some of these have been standardized.
GNU @code{gettext} offers one of these standards.  @xref{Programmers}.

By @dfn{localization}, one means the operation by which, in a set
of programs already internationalized, one gives the program all
needed information so that it can adapt itself to handle its input
and output in a fashion which is correct for some native language and
cultural habits.  This is a particularisation process, by which generic
methods already implemented in an internationalized program are used
in specific ways.  The programming environment puts several functions
to the programmers disposal which allow this runtime configuration.
The formal description of specific set of cultural habits for some
country, together with all associated translations targeted to the
same native language, is called the @dfn{locale} for this language
or country.  Users achieve localization of programs by setting proper
values to special environment variables, prior to executing those
programs, identifying which locale should be used.

In fact, locale message support is only one component of the cultural
data that makes up a particular locale.  There are a whole host of
routines and functions provided to aid programmers in developing
internationalized software and which allow them to access the data
stored in a particular locale.  When someone presently refers to a
particular locale, they are obviously referring to the data stored
within that particular locale.  Similarly, if a programmer is referring
to ``accessing the locale routines'', they are referring to the
complete suite of routines that access all of the locale's information.

One uses the expression @dfn{Native Language Support}, or merely NLS,
for speaking of the overall activity or feature encompassing both
internationalization and localization, allowing for multi-lingual
interactions in a program.  In a nutshell, one could say that
internationalization is the operation by which further localizations
are made possible.

Also, very roughly said, when it comes to multi-lingual messages,
internationalization is usually taken care of by programmers, and
localization is usually taken care of by translators.

@node Aspects, Files, Concepts, Introduction
@section Aspects in Native Language Support

For a totally multi-lingual distribution, there are many things to
translate beyond output messages.

@itemize @bullet
@item
As of today, GNU @code{gettext} offers a complete toolset for
translating messages output by C programs.  Perl scripts and shell
scripts will also need to be translated.  Even if there are today some hooks
by which this can be done, these hooks are not integrated as well as they
should be.

@item
Some programs, like @code{autoconf} or @code{bison}, are able
to produce other programs (or scripts).  Even if the generating
programs themselves are internationalized, the generated programs they
produce may need internationalization on their own, and this indirect
internationalization could be automated right from the generating
program.  In fact, quite usually, generating and generated programs
could be internationalized independently, as the effort needed is
fairly orthogonal.

@item
A few programs include textual tables which might need translation
themselves, independently of the strings contained in the program
itself.  For example, @w{RFC 1345} gives an English description for each
character which the @code{recode} program is able to reconstruct at execution.
Since these descriptions are extracted from the RFC by mechanical means,
translating them properly would require a prior translation of the RFC
itself.

@item
Almost all programs accept options, which are often worded out so to
be descriptive for the English readers; one might want to consider
offering translated versions for program options as well.

@item
Many programs read, interpret, compile, or are somewhat driven by
input files which are texts containing keywords, identifiers, or
replies which are inherently translatable.  For example, one may want
@code{gcc} to allow diacriticized characters in identifiers or use
translated keywords; @samp{rm -i} might accept something else than
@samp{y} or @samp{n} for replies, etc.  Even if the program will
eventually make most of its output in the foreign languages, one has
to decide whether the input syntax, option values, etc., are to be
localized or not.

@item
The manual accompanying a package, as well as all documentation files
in the distribution, could surely be translated, too.  Translating a
manual, with the intent of later keeping up with updates, is a major
undertaking in itself, generally.

@end itemize

As we already stressed, translation is only one aspect of locales.
Other internationalization aspects are system services and are handled
in GNU @code{libc}.  There
are many attributes that are needed to define a country's cultural
conventions.  These attributes include beside the country's native
language, the formatting of the date and time, the representation of
numbers, the symbols for currency, etc.  These local @dfn{rules} are
termed the country's locale.  The locale represents the knowledge
needed to support the country's native attributes.

There are a few major areas which may vary between countries and
hence, define what a locale must describe.  The following list helps
putting multi-lingual messages into the proper context of other tasks
related to locales.  See the GNU @code{libc} manual for details.

@table @emph

@item Characters and Codesets

The codeset most commonly used through out the USA and most English
speaking parts of the world is the ASCII codeset.  However, there are
many characters needed by various locales that are not found within
this codeset.  The 8-bit @w{ISO 8859-1} code set has most of the special
characters needed to handle the major European languages.  However, in
many cases, the @w{ISO 8859-1} font is not adequate.  Hence each locale
will need to specify which codeset they need to use and will need
to have the appropriate character handling routines to cope with
the codeset.

@item Currency

The symbols used vary from country to country as does the position
used by the symbol.  Software needs to be able to transparently
display currency figures in the native mode for each locale.

@item Dates

The format of date varies between locales.  For example, Christmas day
in 1994 is written as 12/25/94 in the USA and as 25/12/94 in Australia.
Other countries might use @w{ISO 8061} dates, etc.

Time of the day may be noted as @var{hh}:@var{mm}, @var{hh}.@var{mm},
or otherwise.  Some locales require time to be specified in 24-hour
mode rather than as AM or PM.  Further, the nature and yearly extent
of the Daylight Saving correction vary widely between countries.

@item Numbers

Numbers can be represented differently in different locales.
For example, the following numbers are all written correctly for
their respective locales:

@example
12,345.67       English
12.345,67       French
1,2345.67       Asia
@end example

Some programs could go further and use different unit systems, like
English units or Metric units, or even take into account variants
about how numbers are spelled in full.

@item Messages

The most obvious area is the language support within a locale.  This is
where GNU @code{gettext} provides the means for developers and users to
easily change the language that the software uses to communicate to
the user.

@end table

Components of locale outside of message handling are standardized in
the ISO C standard and the SUSV2 specification.  GNU @code{libc}
fully implements this, and most other modern systems provide a more
or less reasonable support for at least some of the missing components.

@node Files, Overview, Aspects, Introduction
@section Files Conveying Translations

The letters PO in @file{.po} files means Portable Object, to
distinguish it from @file{.mo} files, where MO stands for Machine
Object.  This paradigm, as well as the PO file format, is inspired
by the NLS standard developed by Uniforum, and implemented by Sun
in their Solaris system.

PO files are meant to be read and edited by humans, and associate each
original, translatable string of a given package with its translation
in a particular target language.  A single PO file is dedicated to
a single target language.  If a package supports many languages,
there is one such PO file per language supported, and each package
has its own set of PO files.  These PO files are best created by
the @code{xgettext} program, and later updated or refreshed through
the @code{msgmerge} program.  Program @code{xgettext} extracts all
marked messages from a set of C files and initializes a PO file with
empty translations.  Program @code{msgmerge} takes care of adjusting
PO files between releases of the corresponding sources, commenting
obsolete entries, initializing new ones, and updating all source
line references.  Files ending with @file{.pot} are kind of base
translation files found in distributions, in PO file format, and
@file{.pox} files are often temporary PO files.

MO files are meant to be read by programs, and are binary in nature.
A few systems already offer tools for creating and handling MO files
as part of the Native Language Support coming with the system, but the
format of these MO files is often different from system to system,
and non-portable.  The tools already provided with these systems don't
support all the features of GNU @code{gettext}.  Therefore GNU
@code{gettext} uses its own format for MO files.  Files ending with
@file{.gmo} are really MO files, when it is known that these files use
the GNU format.

@node Overview,  , Files, Introduction
@section Overview of GNU @code{gettext}

The following diagram summarizes the relation between the files
handled by GNU @code{gettext} and the tools acting on these files.
It is followed by a somewhat detailed explanations, which you should
read while keeping an eye on the diagram.  Having a clear understanding
of these interrelations would surely help programmers, translators
and maintainers.

@example
@group
Original C Sources ---> PO mode ---> Marked C Sources ---.
                                                         |
              .---------<--- GNU gettext Library         |
.--- make <---+                                          |
|             `---------<--------------------+-----------'
|                                            |
|   .-----<--- PACKAGE.pot <--- xgettext <---'   .---<--- PO Compendium
|   |                                            |             ^
|   |                                            `---.         |
|   `---.                                            +---> PO mode ---.
|       +----> msgmerge ------> LANG.pox --->--------'                |
|   .---'                                                             |
|   |                                                                 |
|   `-------------<---------------.                                   |
|                                 +--- LANG.po <--- New LANG.pox <----'
|   .--- LANG.gmo <--- msgfmt <---'
|   |
|   `---> install ---> /.../LANG/PACKAGE.mo ---.
|                                              +---> "Hello world!"
`-------> install ---> /.../bin/PROGRAM -------'
@end group
@end example

The indication @samp{PO mode} appears in two places in this picture,
and you may safely read it as merely meaning ``hand editing'', using
any editor of your choice, really.  However, for those of you being
the lucky users of Emacs, PO mode has been specifically created
for providing a cozy environment for editing or modifying PO files.
While editing a PO file, PO mode allows for the easy browsing of
auxiliary and compendium PO files, as well as for following references into
the set of C program sources from which PO files have been derived.
It has a few special features, among which are the interactive marking
of program strings as translatable, and the validatation of PO files
with easy repositioning to PO file lines showing errors.

As a programmer, the first step to bringing GNU @code{gettext}
into your package is identifying, right in the C sources, those strings
which are meant to be translatable, and those which are untranslatable.
This tedious job can be done a little more comfortably using emacs PO
mode, but you can use any means familiar to you for modifying your
C sources.  Beside this some other simple, standard changes are needed to
properly initialize the translation library.  @xref{Sources}, for
more information about all this.

For newly written software the strings of course can and should be
marked while writing it.  The @code{gettext} approach makes this
very easy.  Simply put the following lines at the beginning of each file
or in a central header file:

@example
@group
#define _(String) (String)
#define N_(String) (String)
#define textdomain(Domain)
#define bindtextdomain(Package, Directory)
@end group
@end example

@noindent
Doing this allows you to prepare the sources for internationalization.
Later when you feel ready for the step to use the @code{gettext} library
simply replace these definitions by the following:

@example
@group
#include <libintl.h>
#define _(String) gettext (String)
#define gettext_noop(String) (String)
#define N_(String) gettext_noop (String)
@end group
@end example

and link against @file{libintl.a} or @file{libintl.so}.  Note that on
GNU systems, you don't need to link with @code{libintl} because the
@code{gettext} library functions are already contained in GNU libc.
That is all you have to change.

Once the C sources have been modified, the @code{xgettext} program
is used to find and extract all translatable strings, and create a
PO template file out of all these.  This @file{@var{package}.pot} file
contains all original program strings.  It has sets of pointers to
exactly where in C sources each string is used.  All translations
are set to empty.  The letter @kbd{t} in @file{.pot} marks this as
a Template PO file, not yet oriented towards any particular language.
@xref{xgettext Invocation}, for more details about how one calls the
@code{xgettext} program.  If you are @emph{really} lazy, you might
be interested at working a lot more right away, and preparing the
whole distribution setup (@pxref{Maintainers}).  By doing so, you
spare yourself typing the @code{xgettext} command, as @code{make}
should now generate the proper things automatically for you!

The first time through, there is no @file{@var{lang}.po} yet, so the
@code{msgmerge} step may be skipped and replaced by a mere copy of
@file{@var{package}.pot} to @file{@var{lang}.pox}, where @var{lang}
represents the target language.

Then comes the initial translation of messages.  Translation in
itself is a whole matter, still exclusively meant for humans,
and whose complexity far overwhelms the level of this manual.
Nevertheless, a few hints are given in some other chapter of this
manual (@pxref{Translators}).  You will also find there indications
about how to contact translating teams, or becoming part of them,
for sharing your translating concerns with others who target the same
native language.

While adding the translated messages into the @file{@var{lang}.pox}
PO file, if you do not have Emacs handy, you are on your own
for ensuring that your efforts fully respect the PO file format, and quoting
conventions (@pxref{PO Files}).  This is surely not an impossible task,
as this is the way many people have handled PO files already for Uniforum or
Solaris.  On the other hand, by using PO mode in Emacs, most details
of PO file format are taken care of for you, but you have to acquire
some familiarity with PO mode itself.  Besides main PO mode commands
(@pxref{Main PO Commands}), you should know how to move between entries
(@pxref{Entry Positioning}), and how to handle untranslated entries
(@pxref{Untranslated Entries}).

If some common translations have already been saved into a compendium
PO file, translators may use PO mode for initializing untranslated
entries from the compendium, and also save selected translations into
the compendium, updating it (@pxref{Compendium}).  Compendium files
are meant to be exchanged between members of a given translation team.

Programs, or packages of programs, are dynamic in nature: users write
bug reports and suggestion for improvements, maintainers react by
modifying programs in various ways.  The fact that a package has
already been internationalized should not make maintainers shy
of adding new strings, or modifying strings already translated.
They just do their job the best they can.  For the Translation
Project to work smoothly, it is important that maintainers do not
carry translation concerns on their already loaded shoulders, and that
translators be kept as free as possible of programmatic concerns.

The only concern maintainers should have is carefully marking new
strings as translatable, when they should be, and do not otherwise
worry about them being translated, as this will come in proper time.
Consequently, when programs and their strings are adjusted in various
ways by maintainers, and for matters usually unrelated to translation,
@code{xgettext} would construct @file{@var{package}.pot} files which are
evolving over time, so the translations carried by @file{@var{lang}.po}
are slowly fading out of date.

It is important for translators (and even maintainers) to understand
that package translation is a continuous process in the lifetime of a
package, and not something which is done once and for all at the start.
After an initial burst of translation activity for a given package,
interventions are needed once in a while, because here and there,
translated entries become obsolete, and new untranslated entries
appear, needing translation.

The @code{msgmerge} program has the purpose of refreshing an already
existing @file{@var{lang}.po} file, by comparing it with a newer
@file{@var{package}.pot} template file, extracted by @code{xgettext}
out of recent C sources.  The refreshing operation adjusts all
references to C source locations for strings, since these strings
move as programs are modified.  Also, @code{msgmerge} comments out as
obsolete, in @file{@var{lang}.pox}, those already translated entries
which are no longer used in the program sources (@pxref{Obsolete
Entries}).  It finally discovers new strings and inserts them in
the resulting PO file as untranslated entries (@pxref{Untranslated
Entries}).  @xref{msgmerge Invocation}, for more information about what
@code{msgmerge} really does.

Whatever route or means taken, the goal is to obtain an updated
@file{@var{lang}.pox} file offering translations for all strings.
When this is properly achieved, this file @file{@var{lang}.pox} may
take the place of the previous official @file{@var{lang}.po} file.

The temporal mobility, or fluidity of PO files, is an integral part of
the translation game, and should be well understood, and accepted.
People resisting it will have a hard time participating in the
Translation Project, or will give a hard time to other participants!  In
particular, maintainers should relax and include all available official
PO files in their distributions, even if these have not recently been
updated, without banging or otherwise trying to exert pressure on the
translator teams to get the job done.  The pressure should rather come
from the community of users speaking a particular language, and
maintainers should consider themselves fairly relieved of any concern
about the adequacy of translation files.  On the other hand, translators
should reasonably try updating the PO files they are responsible for,
while the package is undergoing pretest, prior to an official
distribution.

Once the PO file is complete and dependable, the @code{msgfmt} program
is used for turning the PO file into a machine-oriented format, which
may yield efficient retrieval of translations by the programs of the
package, whenever needed at runtime (@pxref{MO Files}).  @xref{msgfmt
Invocation}, for more information about all modalities of execution
for the @code{msgfmt} program.

Finally, the modified and marked C sources are compiled and linked
with the GNU @code{gettext} library, usually through the operation of
@code{make}, given a suitable @file{Makefile} exists for the project,
and the resulting executable is installed somewhere users will find it.
The MO files themselves should also be properly installed.  Given the
appropriate environment variables are set (@pxref{End Users}), the
program should localize itself automatically, whenever it executes.

The remainder of this manual has the purpose of explaining in depth the various
steps outlined above.

@node Basics, Sources, Introduction, Top
@chapter PO Files and PO Mode Basics

The GNU @code{gettext} toolset helps programmers and translators
at producing, updating and using translation files, mainly those
PO files which are textual, editable files.  This chapter stresses
the format of PO files, and contains a PO mode starter.  PO mode
description is spread throughout this manual instead of being concentrated
in one place.  Here we present only the basics of PO mode.

@menu
* Installation::                Completing GNU @code{gettext} Installation
* PO Files::                    The Format of PO Files
* Main PO Commands::            Main Commands
* Entry Positioning::           Entry Positioning
* Normalizing::                 Normalizing Strings in Entries
@end menu

@node Installation, PO Files, Basics, Basics
@section Completing GNU @code{gettext} Installation

Once you have received, unpacked, configured and compiled the GNU
@code{gettext} distribution, the @samp{make install} command puts in
place the programs @code{xgettext}, @code{msgfmt}, @code{gettext}, and
@code{msgmerge}, as well as their available message catalogs.  To
top off a comfortable installation, you might also want to make the
PO mode available to your Emacs users.

During the installation of the PO mode, you might want to modify your
file @file{.emacs}, once and for all, so it contains a few lines looking
like:

@example
(setq auto-mode-alist
      (cons '("\\.po[tx]?\\'\\|\\.po\\." . po-mode) auto-mode-alist))
(autoload 'po-mode "po-mode" "Major mode for translators to edit PO files" t)
@end example

Later, whenever you edit some @file{.po}, @file{.pot} or @file{.pox}
file, or any file having the string @samp{.po.} within its name,
Emacs loads @file{po-mode.elc} (or @file{po-mode.el}) as needed, and
automatically activates PO mode commands for the associated buffer.
The string @emph{PO} appears in the mode line for any buffer for
which PO mode is active.  Many PO files may be active at once in a
single Emacs session.

If you are using Emacs version 20 or newer, and have already installed
the appropriate international fonts on your system, you may also tell
Emacs how to determine automatically the coding system of every PO file.
This will often (but not always) cause the necessary fonts to be loaded
and used for displaying the translations on your Emacs screen.  For this
to happen, add the lines:

@example
(modify-coding-system-alist 'file "\\.po[tx]?\\'\\|\\.po\\."
                            'po-find-file-coding-system)
(autoload 'po-find-file-coding-system "po-mode")
@end example

@noindent
to your @file{.emacs} file.  If, with this, you still see boxes instead
of international characters, try a different font set (via Shift Mouse
button 1).

@node PO Files, Main PO Commands, Installation, Basics
@section The Format of PO Files

A PO file is made up of many entries, each entry holding the relation
between an original untranslated string and its corresponding
translation.  All entries in a given PO file usually pertain
to a single project, and all translations are expressed in a single
target language.  One PO file @dfn{entry} has the following schematic
structure:

@example
@var{white-space}
#  @var{translator-comments}
#. @var{automatic-comments}
#: @var{reference}@dots{}
#, @var{flag}@dots{}
msgid @var{untranslated-string}
msgstr @var{translated-string}
@end example

The general structure of a PO file should be well understood by
the translator.  When using PO mode, very little has to be known
about the format details, as PO mode takes care of them for her.

Entries begin with some optional white space.  Usually, when generated
through GNU @code{gettext} tools, there is exactly one blank line
between entries.  Then comments follow, on lines all starting with the
character @kbd{#}.  There are two kinds of comments: those which have
some white space immediately following the @kbd{#}, which comments are
created and maintained exclusively by the translator, and those which
have some non-white character just after the @kbd{#}, which comments
are created and maintained automatically by GNU @code{gettext} tools.
All comments, of either kind, are optional.

After white space and comments, entries show two strings, namely
first the untranslated string as it appears in the original program
sources, and then, the translation of this string.  The original
string is introduced by the keyword @code{msgid}, and the translation,
by @code{msgstr}.  The two strings, untranslated and translated,
are quoted in various ways in the PO file, using @kbd{"}
delimiters and @kbd{\} escapes, but the translator does not really
have to pay attention to the precise quoting format, as PO mode fully
takes care of quoting for her.

The @code{msgid} strings, as well as automatic comments, are produced
and managed by other GNU @code{gettext} tools, and PO mode does not
provide means for the translator to alter these.  The most she can
do is merely deleting them, and only by deleting the whole entry.
On the other hand, the @code{msgstr} string, as well as translator
comments, are really meant for the translator, and PO mode gives her
the full control she needs.

The comment lines beginning with @kbd{#,} are special because they are
not completely ignored by the programs as comments generally are.  The
comma separated list of @var{flag}s is used by the @code{msgfmt}
program to give the user some better diagnostic messages.  Currently
there are two forms of flags defined:

@table @kbd
@item fuzzy
This flag can be generated by the @code{msgmerge} program or it can be
inserted by the translator herself.  It shows that the @code{msgstr}
string might not be a correct translation (anymore).  Only the translator
can judge if the translation requires further modification, or is
acceptable as is.  Once satisfied with the translation, she then removes
this @kbd{fuzzy} attribute.  The @code{msgmerge} program inserts this
when it combined the @code{msgid} and @code{msgstr} entries after fuzzy
search only.  @xref{Fuzzy Entries}.

@item c-format
@itemx no-c-format
These flags should not be added by a human.  Instead only the
@code{xgettext} program adds them.  In an automatized PO file processing
system as proposed here the user changes would be thrown away again as
soon as the @code{xgettext} program generates a new template file.

In case the @kbd{c-format} flag is given for a string the @code{msgfmt}
does some more tests to check to validity of the translation.
@xref{msgfmt Invocation}.

@end table

A different kind of entries is used for translations which involve
plural forms.

@example
@var{white-space}
#  @var{translator-comments}
#. @var{automatic-comments}
#: @var{reference}@dots{}
#, @var{flag}@dots{}
msgid @var{untranslated-string-singular}
msgid_plural @var{untranslated-string-plural}
msgstr[0] @var{translated-string-case-0}
...
msgstr[N] @var{translated-string-case-n}
@end example

It happens that some lines, usually whitespace or comments, follow the
very last entry of a PO file.  Such lines are not part of any entry,
and PO mode is unable to take action on those lines.  By using the
PO mode function @w{@kbd{M-x po-normalize}}, the translator may get
rid of those spurious lines.  @xref{Normalizing}.

The remainder of this section may be safely skipped by those using
PO mode, yet it may be interesting for everybody to have a better
idea of the precise format of a PO file.  On the other hand, those
not having Emacs handy should carefully continue reading on.

Each of @var{untranslated-string} and @var{translated-string} respects
the C syntax for a character string, including the surrounding quotes
and imbedded backslashed escape sequences.  When the time comes
to write multi-line strings, one should not use escaped newlines.
Instead, a closing quote should follow the last character on the
line to be continued, and an opening quote should resume the string
at the beginning of the following PO file line.  For example:

@example
msgid ""
"Here is an example of how one might continue a very long string\n"
"for the common case the string represents multi-line output.\n"
@end example

@noindent
In this example, the empty string is used on the first line, to
allow better alignment of the @kbd{H} from the word @samp{Here}
over the @kbd{f} from the word @samp{for}.  In this example, the
@code{msgid} keyword is followed by three strings, which are meant
to be concatenated.  Concatenating the empty string does not change
the resulting overall string, but it is a way for us to comply with
the necessity of @code{msgid} to be followed by a string on the same
line, while keeping the multi-line presentation left-justified, as
we find this to be a cleaner disposition.  The empty string could have
been omitted, but only if the string starting with @samp{Here} was
promoted on the first line, right after @code{msgid}.@footnote{This
limitation is not imposed by GNU @code{gettext}, but is for compatibility
with the @code{msgfmt} implementation on Solaris.} It was not really necessary
either to switch between the two last quoted strings immediately after
the newline @samp{\n}, the switch could have occurred after @emph{any}
other character, we just did it this way because it is neater.

One should carefully distinguish between end of lines marked as
@samp{\n} @emph{inside} quotes, which are part of the represented
string, and end of lines in the PO file itself, outside string quotes,
which have no incidence on the represented string.

Outside strings, white lines and comments may be used freely.
Comments start at the beginning of a line with @samp{#} and extend
until the end of the PO file line.  Comments written by translators
should have the initial @samp{#} immediately followed by some white
space.  If the @samp{#} is not immediately followed by white space,
this comment is most likely generated and managed by specialized GNU
tools, and might disappear or be replaced unexpectedly when the PO
file is given to @code{msgmerge}.

@node Main PO Commands, Entry Positioning, PO Files, Basics
@section Main PO mode Commands

After setting up Emacs with something similar to the lines in
@ref{Installation}, PO mode is activated for a window when Emacs finds a
PO file in that window.  This puts the window read-only and establishes a
po-mode-map, which is a genuine Emacs mode, in a way that is not derived
from text mode in any way.  Functions found on @code{po-mode-hook},
if any, will be executed.

When PO mode is active in a window, the letters @samp{PO} appear
in the mode line for that window.  The mode line also displays how
many entries of each kind are held in the PO file.  For example,
the string @samp{132t+3f+10u+2o} would tell the translator that the
PO mode contains 132 translated entries (@pxref{Translated Entries},
3 fuzzy entries (@pxref{Fuzzy Entries}), 10 untranslated entries
(@pxref{Untranslated Entries}) and 2 obsolete entries (@pxref{Obsolete
Entries}).  Zero-coefficients items are not shown.  So, in this example, if
the fuzzy entries were unfuzzied, the untranslated entries were translated
and the obsolete entries were deleted, the mode line would merely display
@samp{145t} for the counters.

The main PO commands are those which do not fit into the other categories of
subsequent sections.  These allow for quitting PO mode or for managing windows
in special ways.

@table @kbd
@item U
Undo last modification to the PO file.

@item Q
Quit processing and save the PO file.

@item q
Quit processing, possibly after confirmation.

@item O
Temporary leave the PO file window.

@item ?
@itemx h
Show help about PO mode.

@item =
Give some PO file statistics.

@item V
Batch validate the format of the whole PO file.

@end table

The command @kbd{U} (@code{po-undo}) interfaces to the Emacs
@emph{undo} facility.  @xref{Undo, , Undoing Changes, emacs, The Emacs
Editor}.  Each time @kbd{U} is typed, modifications which the translator
did to the PO file are undone a little more.  For the purpose of
undoing, each PO mode command is atomic.  This is especially true for
the @kbd{@key{RET}} command: the whole edition made by using a single
use of this command is undone at once, even if the edition itself
implied several actions.  However, while in the editing window, one
can undo the edition work quite parsimoniously.

The commands @kbd{Q} (@code{po-quit}) and @kbd{q}
(@code{po-confirm-and-quit}) are used when the translator is done with the
PO file.  The former is a bit less verbose than the latter.  If the file
has been modified, it is saved to disk first.  In both cases, and prior to
all this, the commands check if some untranslated message remains in the
PO file and, if yes, the translator is asked if she really wants to leave
off working with this PO file.  This is the preferred way of getting rid
of an Emacs PO file buffer.  Merely killing it through the usual command
@w{@kbd{C-x k}} (@code{kill-buffer}) is not the tidiest way to proceed.

The command @kbd{O} (@code{po-other-window}) is another, softer way,
to leave PO mode, temporarily.  It just moves the cursor to some other
Emacs window, and pops one if necessary.  For example, if the translator
just got PO mode to show some source context in some other, she might
discover some apparent bug in the program source that needs correction.
This command allows the translator to change sex, become a programmer,
and have the cursor right into the window containing the program she
(or rather @emph{he}) wants to modify.  By later getting the cursor back
in the PO file window, or by asking Emacs to edit this file once again,
PO mode is then recovered.

The command @kbd{h} (@code{po-help}) displays a summary of all available PO
mode commands.  The translator should then type any character to resume
normal PO mode operations.  The command @kbd{?} has the same effect
as @kbd{h}.

The command @kbd{=} (@code{po-statistics}) computes the total number of
entries in the PO file, the ordinal of the current entry (counted from
1), the number of untranslated entries, the number of obsolete entries,
and displays all these numbers.

The command @kbd{V} (@code{po-validate}) launches @code{msgfmt} in verbose
mode over the current PO file.  This command first offers to save the
current PO file on disk.  The @code{msgfmt} tool, from GNU @code{gettext},
has the purpose of creating a MO file out of a PO file, and PO mode uses
the features of this program for checking the overall format of a PO file,
as well as all individual entries.

The program @code{msgfmt} runs asynchronously with Emacs, so the
translator regains control immediately while her PO file is being studied.
Error output is collected in the Emacs @samp{*compilation*} buffer,
displayed in another window.  The regular Emacs command @kbd{C-x`}
(@code{next-error}), as well as other usual compile commands, allow the
translator to reposition quickly to the offending parts of the PO file.
Once the cursor is on the line in error, the translator may decide on
any PO mode action which would help correcting the error.

@node Entry Positioning, Normalizing, Main PO Commands, Basics
@section Entry Positioning

The cursor in a PO file window is almost always part of
an entry.  The only exceptions are the special case when the cursor
is after the last entry in the file, or when the PO file is
empty.  The entry where the cursor is found to be is said to be the
current entry.  Many PO mode commands operate on the current entry,
so moving the cursor does more than allowing the translator to browse
the PO file, this also selects on which entry commands operate.

Some PO mode commands alter the position of the cursor in a specialized
way.  A few of those special purpose positioning are described here,
the others are described in following sections.

@table @kbd

@item .
Redisplay the current entry.

@item n
@itemx n
Select the entry after the current one.

@item p
@itemx p
Select the entry before the current one.

@item <
Select the first entry in the PO file.

@item >
Select the last entry in the PO file.

@item m
Record the location of the current entry for later use.

@item l
Return to a previously saved entry location.

@item x
Exchange the current entry location with the previously saved one.

@end table

Any Emacs command able to reposition the cursor may be used
to select the current entry in PO mode, including commands which
move by characters, lines, paragraphs, screens or pages, and search
commands.  However, there is a kind of standard way to display the
current entry in PO mode, which usual Emacs commands moving
the cursor do not especially try to enforce.  The command @kbd{.}
(@code{po-current-entry}) has the sole purpose of redisplaying the
current entry properly, after the current entry has been changed by
means external to PO mode, or the Emacs screen otherwise altered.

It is yet to be decided if PO mode helps the translator, or otherwise
irritates her, by forcing a rigid window disposition while she
is doing her work.  We originally had quite precise ideas about
how windows should behave, but on the other hand, anyone used to
Emacs is often happy to keep full control.  Maybe a fixed window
disposition might be offered as a PO mode option that the translator
might activate or deactivate at will, so it could be offered on an
experimental basis.  If nobody feels a real need for using it, or
a compulsion for writing it, we should drop this whole idea.
The incentive for doing it should come from translators rather than
programmers, as opinions from an experienced translator are surely
more worth to me than opinions from programmers @emph{thinking} about
how @emph{others} should do translation.

The commands @kbd{n} (@code{po-next-entry}) and @kbd{p}
(@code{po-previous-entry}) move the cursor the entry following,
or preceding, the current one.  If @kbd{n} is given while the
cursor is on the last entry of the PO file, or if @kbd{p}
is given while the cursor is on the first entry, no move is done.

The commands @kbd{<} (@code{po-first-entry}) and @kbd{>}
(@code{po-last-entry}) move the cursor to the first entry, or last
entry, of the PO file.  When the cursor is located past the last
entry in a PO file, most PO mode commands will return an error saying
@samp{After last entry}.  Moreover, the commands @kbd{<} and @kbd{>}
have the special property of being able to work even when the cursor
is not into some PO file entry, and one may use them for nicely
correcting this situation.  But even these commands will fail on a
truly empty PO file.  There are development plans for the PO mode for it
to interactively fill an empty PO file from sources.  @xref{Marking}.

The translator may decide, before working at the translation of
a particular entry, that she needs to browse the remainder of the
PO file, maybe for finding the terminology or phraseology used
in related entries.  She can of course use the standard Emacs idioms
for saving the current cursor location in some register, and use that
register for getting back, or else, use the location ring.

PO mode offers another approach, by which cursor locations may be saved
onto a special stack.  The command @kbd{m} (@code{po-push-location})
merely adds the location of current entry to the stack, pushing
the already saved locations under the new one.  The command
@kbd{r} (@code{po-pop-location}) consumes the top stack element and
repositions the cursor to the entry associated with that top element.
This position is then lost, for the next @kbd{r} will move the cursor
to the previously saved location, and so on until no locations remain
on the stack.

If the translator wants the position to be kept on the location stack,
maybe for taking a look at the entry associated with the top
element, then go elsewhere with the intent of getting back later, she
ought to use @kbd{m} immediately after @kbd{r}.

The command @kbd{x} (@code{po-exchange-location}) simultaneously
repositions the cursor to the entry associated with the top element of
the stack of saved locations, and replaces that top element with the
location of the current entry before the move.  Consequently, repeating
the @kbd{x} command toggles alternatively between two entries.
For achieving this, the translator will position the cursor on the
first entry, use @kbd{m}, then position to the second entry, and
merely use @kbd{x} for making the switch.

@node Normalizing,  , Entry Positioning, Basics
@section Normalizing Strings in Entries

There are many different ways for encoding a particular string into a
PO file entry, because there are so many different ways to split and
quote multi-line strings, and even, to represent special characters
by backslahsed escaped sequences.  Some features of PO mode rely on
the ability for PO mode to scan an already existing PO file for a
particular string encoded into the @code{msgid} field of some entry.
Even if PO mode has internally all the built-in machinery for
implementing this recognition easily, doing it fast is technically
difficult.  To facilitate a solution to this efficiency problem,
we decided on a canonical representation for strings.

A conventional representation of strings in a PO file is currently
under discussion, and PO mode experiments with a canonical representation.
Having both @code{xgettext} and PO mode converging towards a uniform
way of representing equivalent strings would be useful, as the internal
normalization needed by PO mode could be automatically satisfied
when using @code{xgettext} from GNU @code{gettext}.  An explicit
PO mode normalization should then be only necessary for PO files
imported from elsewhere, or for when the convention itself evolves.

So, for achieving normalization of at least the strings of a given
PO file needing a canonical representation, the following PO mode
command is available:

@table @kbd
@item M-x po-normalize
Tidy the whole PO file by making entries more uniform.

@end table

The special command @kbd{M-x po-normalize}, which has no associated
keys, revises all entries, ensuring that strings of both original
and translated entries use uniform internal quoting in the PO file.
It also removes any crumb after the last entry.  This command may be
useful for PO files freshly imported from elsewhere, or if we ever
improve on the canonical quoting format we use.  This canonical format
is not only meant for getting cleaner PO files, but also for greatly
speeding up @code{msgid} string lookup for some other PO mode commands.

@kbd{M-x po-normalize} presently makes three passes over the entries.
The first implements heuristics for converting PO files for GNU
@code{gettext} 0.6 and earlier, in which @code{msgid} and @code{msgstr}
fields were using K&R style C string syntax for multi-line strings.
These heuristics may fail for comments not related to obsolete
entries and ending with a backslash; they also depend on subsequent
passes for finalizing the proper commenting of continued lines for
obsolete entries.  This first pass might disappear once all oldish PO
files would have been adjusted.  The second and third pass normalize
all @code{msgid} and @code{msgstr} strings respectively.  They also
clean out those trailing backslashes used by XView's @code{msgfmt}
for continued lines.

Having such an explicit normalizing command allows for importing PO
files from other sources, but also eases the evolution of the current
convention, evolution driven mostly by aesthetic concerns, as of now.
It is easy to make suggested adjustments at a later time, as the
normalizing command and eventually, other GNU @code{gettext} tools
should greatly automate conformance.  A description of the canonical
string format is given below, for the particular benefit of those not
having Emacs handy, and who would nevertheless want to handcraft
their PO files in nice ways.

Right now, in PO mode, strings are single line or multi-line.  A string
goes multi-line if and only if it has @emph{embedded} newlines, that
is, if it matches @samp{[^\n]\n+[^\n]}.  So, we would have:

@example
msgstr "\n\nHello, world!\n\n\n"
@end example

but, replacing the space by a newline, this becomes:

@example
msgstr ""
"\n"
"\n"
"Hello,\n"
"world!\n"
"\n"
"\n"
@end example

We are deliberately using a caricatural example, here, to make the
point clearer.  Usually, multi-lines are not that bad looking.
It is probable that we will implement the following suggestion.
We might lump together all initial newlines into the empty string,
and also all newlines introducing empty lines (that is, for @w{@var{n}
> 1}, the @var{n}-1'th last newlines would go together on a separate
string), so making the previous example appear:

@example
msgstr "\n\n"
"Hello,\n"
"world!\n"
"\n\n"
@end example

There are a few yet undecided little points about string normalization,
to be documented in this manual, once these questions settle.

@node Sources, Template, Basics, Top
@chapter Preparing Program Sources

@c FIXME: Rewrite (the whole chapter).

For the programmer, changes to the C source code fall into three
categories.  First, you have to make the localization functions
known to all modules needing message translation.  Second, you should
properly trigger the operation of GNU @code{gettext} when the program
initializes, usually from the @code{main} function.  Last, you should
identify and especially mark all constant strings in your program
needing translation.

Presuming that your set of programs, or package, has been adjusted
so all needed GNU @code{gettext} files are available, and your
@file{Makefile} files are adjusted (@pxref{Maintainers}), each C module
having translated C strings should contain the line:

@example
#include <libintl.h>
@end example

The remaining changes to your C sources are discussed in the further
sections of this chapter.

@menu
* Triggering::                  Triggering @code{gettext} Operations
* Mark Keywords::               How Marks Appear in Sources
* Marking::                     Marking Translatable Strings
* c-format::                    Telling something about the following string
* Special cases::               Special Cases of Translatable Strings
@end menu

@node Triggering, Mark Keywords, Sources, Sources
@section Triggering @code{gettext} Operations

The initialization of locale data should be done with more or less
the same code in every program, as demonstrated below:

@example
@group
int
main (argc, argv)
     int argc;
     char argv;
@{
  @dots{}
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);
  @dots{}
@}
@end group
@end example

@var{PACKAGE} and @var{LOCALEDIR} should be provided either by
@file{config.h} or by the Makefile.  For now consult the @code{gettext}
sources for more information.

The use of @code{LC_ALL} might not be appropriate for you.
@code{LC_ALL} includes all locale categories and especially
@code{LC_CTYPE}.  This later category is responsible for determining
character classes with the @code{isalnum} etc. functions from
@file{ctype.h} which could especially for programs, which process some
kind of input language, be wrong.  For example this would mean that a
source code using the @,{c} (c-cedilla character) is runnable in
France but not in the U.S.

Some systems also have problems with parsing numbers using the
@code{scanf} functions if an other but the @code{LC_ALL} locale is used.
The standards say that additional formats but the one known in the
@code{"C"} locale might be recognized.  But some systems seem to reject
numbers in the @code{"C"} locale format.  In some situation, it might
also be a problem with the notation itself which makes it impossible to
recognize whether the number is in the @code{"C"} locale or the local
format.  This can happen if thousands separator characters are used.
Some locales define this character accordfing to the national
conventions to @code{'.'} which is the same character used in the
@code{"C"} locale to denote the decimal point.

So it is sometimes necessary to replace the @code{LC_ALL} line in the
code above by a sequence of @code{setlocale} lines

@example
@group
@{
  @dots{}
  setlocale (LC_CTYPE, "");
  setlocale (LC_MESSAGES, "");
  @dots{}
@}
@end group
@end example

@noindent
On all POSIX conformant systems the locale categories @code{LC_CTYPE},
@code{LC_COLLATE}, @code{LC_MONETARY}, @code{LC_NUMERIC}, and
@code{LC_TIME} are available.  On some modern systems there is also a
locale @code{LC_MESSAGES} which is called on some old, XPG2 compliant
systems @code{LC_RESPONSES}.

Note that changing the @code{LC_CTYPE} also affects the functions
declared in the @code{<ctype.h>} standard header.  If this is not
desirable in your application (for example in a compiler's parser),
you can use a set of substitute functions which hardwire the C locale,
such as found in the @code{<c-ctype.h>} and @code{<c-ctype.c>} files
in the gettext source distribution.

It is also possible to switch the locale forth and back between the
environment dependent locale and the C locale, but this approach is
normally avoided because a @code{setlocale} call is expensive,
because it is tedious to determine the places where a locale switch
is needed in a large program's source, and because switching a locale
is not multithread-safe.

@node Mark Keywords, Marking, Triggering, Sources
@section How Marks Appear in Sources

All strings requiring translation should be marked in the C sources.  Marking
is done in such a way that each translatable string appears to be
the sole argument of some function or preprocessor macro.  There are
only a few such possible functions or macros meant for translation,
and their names are said to be marking keywords.  The marking is
attached to strings themselves, rather than to what we do with them.
This approach has more uses.  A blatant example is an error message
produced by formatting.  The format string needs translation, as
well as some strings inserted through some @samp{%s} specification
in the format, while the result from @code{sprintf} may have so many
different instances that it is impractical to list them all in some
@samp{error_string_out()} routine, say.

This marking operation has two goals.  The first goal of marking
is for triggering the retrieval of the translation, at run time.
The keyword are possibly resolved into a routine able to dynamically
return the proper translation, as far as possible or wanted, for the
argument string.  Most localizable strings are found in executable
positions, that is, attached to variables or given as parameters to
functions.  But this is not universal usage, and some translatable
strings appear in structured initializations.  @xref{Special cases}.

The second goal of the marking operation is to help @code{xgettext}
at properly extracting all translatable strings when it scans a set
of program sources and produces PO file templates.

The canonical keyword for marking translatable strings is
@samp{gettext}, it gave its name to the whole GNU @code{gettext}
package.  For packages making only light use of the @samp{gettext}
keyword, macro or function, it is easily used @emph{as is}.  However,
for packages using the @code{gettext} interface more heavily, it
is usually more convenient to give the main keyword a shorter, less
obtrusive name.  Indeed, the keyword might appear on a lot of strings
all over the package, and programmers usually do not want nor need
their program sources to remind them forcefully, all the time, that they
are internationalized.  Further, a long keyword has the disadvantage
of using more horizontal space, forcing more indentation work on
sources for those trying to keep them within 79 or 80 columns.

Many packages use @samp{_} (a simple underline) as a keyword,
and write @samp{_("Translatable string")} instead of @samp{gettext
("Translatable string")}.  Further, the coding rule, from GNU standards,
wanting that there is a space between the keyword and the opening
parenthesis is relaxed, in practice, for this particular usage.
So, the textual overhead per translatable string is reduced to
only three characters: the underline and the two parentheses.
However, even if GNU @code{gettext} uses this convention internally,
it does not offer it officially.  The real, genuine keyword is truly
@samp{gettext} indeed.  It is fairly easy for those wanting to use
@samp{_} instead of @samp{gettext} to declare:

@example
#include <libintl.h>
#define _(String) gettext (String)
@end example

@noindent
instead of merely using @samp{#include <libintl.h>}.

Later on, the maintenance is relatively easy.  If, as a programmer,
you add or modify a string, you will have to ask yourself if the
new or altered string requires translation, and include it within
@samp{_()} if you think it should be translated.  @samp{"%s: %d"} is
an example of string @emph{not} requiring translation!

@node Marking, c-format, Mark Keywords, Sources
@section Marking Translatable Strings

In PO mode, one set of features is meant more for the programmer than
for the translator, and allows him to interactively mark which strings,
in a set of program sources, are translatable, and which are not.
Even if it is a fairly easy job for a programmer to find and mark
such strings by other means, using any editor of his choice, PO mode
makes this work more comfortable.  Further, this gives translators
who feel a little like programmers, or programmers who feel a little
like translators, a tool letting them work at marking translatable
strings in the program sources, while simultaneously producing a set of
translation in some language, for the package being internationalized.

The set of program sources, targetted by the PO mode commands describe
here, should have an Emacs tags table constructed for your project,
prior to using these PO file commands.  This is easy to do.  In any
shell window, change the directory to the root of your project, then
execute a command resembling:

@example
etags src/*.[hc] lib/*.[hc]
@end example

@noindent
presuming here you want to process all @file{.h} and @file{.c} files
from the @file{src/} and @file{lib/} directories.  This command will
explore all said files and create a @file{TAGS} file in your root
directory, somewhat summarizing the contents using a special file
format Emacs can understand.

For packages following the GNU coding standards, there is
a make goal @code{tags} or @code{TAGS} which constructs the tag files in
all directories and for all files containing source code.

Once your @file{TAGS} file is ready, the following commands assist
the programmer at marking translatable strings in his set of sources.
But these commands are necessarily driven from within a PO file
window, and it is likely that you do not even have such a PO file yet.
This is not a problem at all, as you may safely open a new, empty PO
file, mainly for using these commands.  This empty PO file will slowly
fill in while you mark strings as translatable in your program sources.

@table @kbd
@item ,
Search through program sources for a string which looks like a
candidate for translation.

@item M-,
Mark the last string found with @samp{_()}.

@item M-.
Mark the last string found with a keyword taken from a set of possible
keywords.  This command with a prefix allows some management of these
keywords.

@end table

The @kbd{,} (@code{po-tags-search}) command searches for the next
occurrence of a string which looks like a possible candidate for
translation, and displays the program source in another Emacs window,
positioned in such a way that the string is near the top of this other
window.  If the string is too big to fit whole in this window, it is
positioned so only its end is shown.  In any case, the cursor
is left in the PO file window.  If the shown string would be better
presented differently in different native languages, you may mark it
using @kbd{M-,} or @kbd{M-.}.  Otherwise, you might rather ignore it
and skip to the next string by merely repeating the @kbd{,} command.

A string is a good candidate for translation if it contains a sequence
of three or more letters.  A string containing at most two letters in
a row will be considered as a candidate if it has more letters than
non-letters.  The command disregards strings containing no letters,
or isolated letters only.  It also disregards strings within comments,
or strings already marked with some keyword PO mode knows (see below).

If you have never told Emacs about some @file{TAGS} file to use, the
command will request that you specify one from the minibuffer, the
first time you use the command.  You may later change your @file{TAGS}
file by using the regular Emacs command @w{@kbd{M-x visit-tags-table}},
which will ask you to name the precise @file{TAGS} file you want
to use.  @xref{Tags, , Tag Tables, emacs, The Emacs Editor}.

Each time you use the @kbd{,} command, the search resumes from where it was
left by the previous search, and goes through all program sources,
obeying the @file{TAGS} file, until all sources have been processed.
However, by giving a prefix argument to the command @w{(@kbd{C-u
,})}, you may request that the search be restarted all over again
from the first program source; but in this case, strings that you
recently marked as translatable will be automatically skipped.

Using this @kbd{,} command does not prevent using of other regular
Emacs tags commands.  For example, regular @code{tags-search} or
@code{tags-query-replace} commands may be used without disrupting the
independent @kbd{,} search sequence.  However, as implemented, the
@emph{initial} @kbd{,} command (or the @kbd{,} command is used with a
prefix) might also reinitialize the regular Emacs tags searching to the
first tags file, this reinitialization might be considered spurious.

The @kbd{M-,} (@code{po-mark-translatable}) command will mark the
recently found string with the @samp{_} keyword.  The @kbd{M-.}
(@code{po-select-mark-and-mark}) command will request that you type
one keyword from the minibuffer and use that keyword for marking
the string.  Both commands will automatically create a new PO file
untranslated entry for the string being marked, and make it the
current entry (making it easy for you to immediately proceed to its
translation, if you feel like doing it right away).  It is possible
that the modifications made to the program source by @kbd{M-,} or
@kbd{M-.} render some source line longer than 80 columns, forcing you
to break and re-indent this line differently.  You may use the @kbd{O}
command from PO mode, or any other window changing command from
Emacs, to break out into the program source window, and do any
needed adjustments.  You will have to use some regular Emacs command
to return the cursor to the PO file window, if you want command
@kbd{,} for the next string, say.

The @kbd{M-.} command has a few built-in speedups, so you do not
have to explicitly type all keywords all the time.  The first such
speedup is that you are presented with a @emph{preferred} keyword,
which you may accept by merely typing @kbd{@key{RET}} at the prompt.
The second speedup is that you may type any non-ambiguous prefix of the
keyword you really mean, and the command will complete it automatically
for you.  This also means that PO mode has to @emph{know} all
your possible keywords, and that it will not accept mistyped keywords.

If you reply @kbd{?} to the keyword request, the command gives a
list of all known keywords, from which you may choose.  When the
command is prefixed by an argument @w{(@kbd{C-u M-.})}, it inhibits
updating any program source or PO file buffer, and does some simple
keyword management instead.  In this case, the command asks for a
keyword, written in full, which becomes a new allowed keyword for
later @kbd{M-.} commands.  Moreover, this new keyword automatically
becomes the @emph{preferred} keyword for later commands.  By typing
an already known keyword in response to @w{@kbd{C-u M-.}}, one merely
changes the @emph{preferred} keyword and does nothing more.

All keywords known for @kbd{M-.} are recognized by the @kbd{,} command
when scanning for strings, and strings already marked by any of those
known keywords are automatically skipped.  If many PO files are opened
simultaneously, each one has its own independent set of known keywords.
There is no provision in PO mode, currently, for deleting a known
keyword, you have to quit the file (maybe using @kbd{q}) and reopen
it afresh.  When a PO file is newly brought up in an Emacs window, only
@samp{gettext} and @samp{_} are known as keywords, and @samp{gettext}
is preferred for the @kbd{M-.} command.  In fact, this is not useful to
prefer @samp{_}, as this one is already built in the @kbd{M-,} command.

@node c-format, Special cases, Marking, Sources
@section Special Comments preceding Keywords

@c FIXME document c-format and no-c-format.

In C programs strings are often used within calls of functions from the
@code{printf} family.  The special thing about these format strings is
that they can contain format specifiers introduced with @kbd{%}.  Assume
we have the code

@example
printf (gettext ("String `%s' has %d characters\n"), s, strlen (s));
@end example

@noindent
A possible German translation for the above string might be:

@example
"%d Zeichen lang ist die Zeichenkette `%s'"
@end example

A C programmer, even if he cannot speak German, will recognize that
there is something wrong here.  The order of the two format specifiers
is changed but of course the arguments in the @code{printf} don't have.
This will most probably lead to problems because now the length of the
string is regarded as the address.

To prevent errors at runtime caused by translations the @code{msgfmt}
tool can check statically whether the arguments in the original and the
translation string match in type and number.  If this is not the case a
warning will be given and the error cannot causes problems at runtime.

@noindent
If the word order in the above German translation would be correct one
would have to write

@example
"%2$d Zeichen lang ist die Zeichenkette `%1$s'"
@end example

@noindent
The routines in @code{msgfmt} know about this special notation.

Because not all strings in a program must be format strings it is not
useful for @code{msgfmt} to test all the strings in the @file{.po} file.
This might cause problems because the string might contain what looks
like a format specifier, but the string is not used in @code{printf}.

Therefore the @code{xgettext} adds a special tag to those messages it
thinks might be a format string.  There is no absolute rule for this,
only a heuristic.  In the @file{.po} file the entry is marked using the
@code{c-format} flag in the @kbd{#,} comment line (@pxref{PO Files}).

The careful reader now might say that this again can cause problems.
The heuristic might guess it wrong.  This is true and therefore
@code{xgettext} knows about special kind of comment which lets
the programmer take over the decision.  If in the same line or
the immediately preceding line of the @code{gettext} keyword
the @code{xgettext} program find a comment containing the words
@kbd{xgettext:c-format} it will mark the string in any case with
the @kbd{c-format} flag.  This kind of comment should be used when
@code{xgettext} does not recognize the string as a format string but
is really is one and it should be tested.  Please note that when the
comment is in the same line of the @code{gettext} keyword, it must be
before the string to be translated.

This situation happens quite often.  The @code{printf} function is often
called with strings which do not contain a format specifier.  Of course
one would normally use @code{fputs} but it does happen.  In this case
@code{xgettext} does not recognize this as a format string but what
happens if the translation introduces a valid format specifier?  The
@code{printf} function will try to access one of the parameter but none
exists because the original code does not refer to any parameter.

@code{xgettext} of course could make a wrong decision the other way
round, i.e. a string marked as a format string actually is not a format
string.  In this case the @code{msgfmt} might give too many warnings and
would prevent translating the @file{.po} file.  The method to prevent
this wrong decision is similar to the one used above, only the comment
to use must contain the string @kbd{xgettext:no-c-format}.

If a string is marked with @kbd{c-format} and this is not correct the
user can find out who is responsible for the decision.  See
@ref{xgettext Invocation} to see how the @kbd{--debug} option can be
used for solving this problem.

@node Special cases,  , c-format, Sources
@section Special Cases of Translatable Strings

The attentive reader might now point out that it is not always possible
to mark translatable string with @code{gettext} or something like this.
Consider the following case:

@example
@group
@{
  static const char *messages[] = @{
    "some very meaningful message",
    "and another one"
  @};
  const char *string;
  @dots{}
  string
    = index > 1 ? "a default message" : messages[index];

  fputs (string);
  @dots{}
@}
@end group
@end example

While it is no problem to mark the string @code{"a default message"} it
is not possible to mark the string initializers for @code{messages}.
What is to be done?  We have to fulfill two tasks.  First we have to mark the
strings so that the @code{xgettext} program (@pxref{xgettext Invocation})
can find them, and second we have to translate the string at runtime
before printing them.

The first task can be fulfilled by creating a new keyword, which names a
no-op.  For the second we have to mark all access points to a string
from the array.  So one solution can look like this:

@example
@group
#define gettext_noop(String) (String)

@{
  static const char *messages[] = @{
    gettext_noop ("some very meaningful message"),
    gettext_noop ("and another one")
  @};
  const char *string;
  @dots{}
  string
    = index > 1 ? gettext ("a default message") : gettext (messages[index]);

  fputs (string);
  @dots{}
@}
@end group
@end example

Please convince yourself that the string which is written by
@code{fputs} is translated in any case.  How to get @code{xgettext} know
the additional keyword @code{gettext_noop} is explained in @ref{xgettext
Invocation}.

The above is of course not the only solution.  You could also come along
with the following one:

@example
@group
#define gettext_noop(String) (String)

@{
  static const char *messages[] = @{
    gettext_noop ("some very meaningful message",
    gettext_noop ("and another one")
  @};
  const char *string;
  @dots{}
  string
    = index > 1 ? gettext_noop ("a default message") : messages[index];

  fputs (gettext (string));
  @dots{}
@}
@end group
@end example

But this has some drawbacks.  First the programmer has to take care that
he uses @code{gettext_noop} for the string @code{"a default message"}.
A use of @code{gettext} could have in rare cases unpredictable results.
The second reason is found in the internals of the GNU @code{gettext}
Library which will make this solution less efficient.

One advantage is that you need not make control flow analysis to make
sure the output is really translated in any case.  But this analysis is
generally not very difficult.  If it should be in any situation you can
use this second method in this situation.

@node Template, Creating, Sources, Top
@chapter Making the PO Template File

After preparing the sources, the programmer creates a PO template file.
This section explains how to use @code{xgettext} for this purpose.

@c FIXME: Rewrite.

@menu
* xgettext Invocation::         Invoking the @code{xgettext} Program
@end menu

@node xgettext Invocation,  , Template, Template
@section Invoking the @code{xgettext} Program

@c FIXME: Rewrite.

@example
xgettext [@var{option}] @var{inputfile} @dots{}
@end example

@table @samp
@item -a
@itemx --extract-all
Extract all strings.

@item -c [@var{tag}]
@itemx --add-comments[=@var{tag}]
Place comment block with @var{tag} (or those preceding keyword lines)
in output file.

@item -C
@itemx --c++
Recognize C++ style comments.

@itemx --debug
Use the flags @kbd{c-format} and @kbd{possible-c-format} to show who was
responsible for marking a message as a format string.  The latter form is
used if the @code{xgettext} program decided, the format form is used if
the programmer prescribed it.

By default only the @kbd{c-format} form is used.  The translator should
not have to care about these details.

@item -d @var{name}
@itemx --default-domain=@var{name}
Use @file{@var{name}.po} for output (instead of @file{messages.po}).

The special domain name @file{-} or @file{/dev/stdout} means to write
the output to @file{stdout}.

@item -D @var{directory}
@itemx --directory=@var{directory}
Change to @var{directory} before beginning to search and scan source
files.  The resulting @file{.po} file will be written relative to the
original directory, though.

@item -f @var{file}
@itemx --files-from=@var{file}
Read the names of the input files from @var{file} instead of getting
them from the command line.

@itemx --force
Always write an output file even if no message is defined.

@item -h
@itemx --help
Display this help and exit.

@item -I @var{list}
@itemx --input-path=@var{list}
List of directories searched for input files.

@item -j
@itemx --join-existing
Join messages with existing file.

@item -k @var{word}
@itemx --keyword[=@var{keywordspec}]
Additional keyword to be looked for (without @var{keywordspec} means not to
use default keywords).

If @var{keywordspec} is a C identifer @var{id}, @code{xgettext} looks
for strings in the first argument of each call to the function or macro
@var{id}.  If @var{keywordspec} is of the form
@samp{@var{id}:@var{argnum}}, @code{xgettext} looks for strings in the
@var{argnum}th argument of the call.  If @var{keywordspec} is of the form
@samp{@var{id}:@var{argnum1},@var{argnum2}}, @code{xgettext} looks for
strings in the @var{argnum1}st argument and in the @var{argnum2}nd argument
of the call, and treats them as singular/plural variants for a message
with plural handling.

The default keyword specifications, which are always looked for if not
explicitly disabled, are @code{gettext}, @code{dgettext:2},
@code{dcgettext:2}, @code{ngettext:1,2}, @code{dngettext:2,3},
@code{dcngettext:2,3}, and @code{gettext_noop}.

@item -m [@var{string}]
@itemx --msgstr-prefix[=@var{string}]
Use @var{string} or "" as prefix for msgstr entries.

@item -M [@var{string}]
@itemx --msgstr-suffix[=@var{string}]
Use @var{string} or "" as suffix for msgstr entries.

@item --no-location
Do not write @samp{#: @var{filename}:@var{line}} lines.

@item -n
@itemx --add-location
Generate @samp{#: @var{filename}:@var{line}} lines (default).

@item --omit-header
Don't write header with @samp{msgid ""} entry.

This is useful for testing purposes because it eliminates a source
of variance for generated @code{.gmo} files.  We can ship some of
these files in the GNU @code{gettext} package, and the result of
regenerating them through @code{msgfmt} should yield the same values.

@item -p @var{dir}
@itemx --output-dir=@var{dir}
Output files will be placed in directory @var{dir}.

@item -s
@itemx --sort-output
Generate sorted output and remove duplicates.

@item --strict
Write out a strict Uniforum conforming PO file.

@item -v
@itemx --version
Output version information and exit.

@item -x @var{file}
@itemx --exclude-file=@var{file}
Entries from @var{file} are not extracted.

@end table

Search path for supplementary PO files is:
@file{/usr/local/share/nls/src/}.

If @var{inputfile} is @samp{-}, standard input is read.

This implementation of @code{xgettext} is able to process a few awkward
cases, like strings in preprocessor macros, ANSI concatenation of
adjacent strings, and escaped end of lines for continued strings.

@node Creating, Updating, Template, Top
@chapter Creating a New PO File

When starting a new translation, the translator copies the
@file{@var{package}.pot} template file to a file called
@file{@var{LANG}.po}.  Then she modifies the initial comments and
the header entry of this file.

The initial comments "SOME DESCRIPTIVE TITLE", "YEAR" and
"FIRST AUTHOR <EMAIL@@ADDRESS>, YEAR" ought to be replaced by sensible
information.  This can be done in any text editor; if Emacs is used
and it switched to PO mode automatically (because it has recognized
the file's suffix), you can disable it by typing @kbd{M-x fundamental-mode}.

Modifying the header entry can already be done using PO mode: in Emacs,
type @kbd{M-x po-mode RET} and then @kbd{RET} again to start editing the
entry.  You should fill in the following fields.

@table @asis
@item Project-Id-Version
This is the name and version of the package.

@item POT-Creation-Date
This has already been filled in by @code{xgettext}.

@item PO-Revision-Date
You don't need to fill this in. It will be filled by the Emacs PO mode
when you save the file.

@item Last-Translator
Fill in your name and email address (without double quotes).

@item Language-Team
Fill in the English name of the language, and the email address of the
language team you are part of.

Before starting a translation, it is a good idea to get in touch with
your translation team, not only to make sure you don't do duplicated work,
but also to coordinate difficult linguistic issues.

In the Free Translation Project, each translation team has its own mailing
list.  The up-to-date list of teams can be found at the Free Translation
Project's homepage, @file{http://www.iro.umontreal.ca/contrib/po/HTML/},
in the "National teams" area.

@item Content-Type
Replace @samp{CHARSET} with the character encoding used for your language,
in your locale, or UTF-8.  This field is needed for correct operation of the
@code{msgmerge} and @code{msgfmt} programs, as well as for users whose
locale's character encoding differs from yours (see @ref{Charset conversion}).

You get the character encoding of your locale by running the shell command
@samp{locale charmap}.  If the result is @samp{C} or @samp{ANSI_X3.4-1968},
which is equivalent to @samp{ASCII} (= @samp{US-ASCII}), it means that your
locale is not correctly configured.  In this case, ask your translation
team which charset to use.  @samp{ASCII} is not usable for any language
except Latin.

Because the PO files must be portable to operating systems with less advanced
internationalization facilities, the character encodings that can be used
are limited to those supported by both GNU @code{libc} and GNU
@code{libiconv}. These are:
@code{ASCII}, @code{ISO-8859-1}, @code{ISO-8859-2}, @code{ISO-8859-3},
@code{ISO-8859-4}, @code{ISO-8859-5}, @code{ISO-8859-6}, @code{ISO-8859-7},
@code{ISO-8859-8}, @code{ISO-8859-9}, @code{ISO-8859-13}, @code{ISO-8859-15},
@code{KOI8-R}, @code{KOI8-U}, @code{CP850}, @code{CP866}, @code{CP874},
@code{CP932}, @code{CP949}, @code{CP950}, @code{CP1250}, @code{CP1251},
@code{CP1252}, @code{CP1253}, @code{CP1254}, @code{CP1255}, @code{CP1256},
@code{CP1257}, @code{GB2312}, @code{EUC-JP}, @code{EUC-KR}, @code{EUC-TW},
@code{BIG5}, @code{BIG5-HKSCS}, @code{GBK}, @code{GB18030}, @code{SHIFT_JIS},
@code{JOHAB}, @code{TIS-620}, @code{VISCII}, @code{UTF-8}.

@c This data is taken from glibc/localedata/SUPPORTED.
In the GNU system, the following encodings are frequently used for the
corresponding languages.

@itemize
@item @code{ISO-8859-1} for
 Afrikaans, Albanian, Basque, Catalan, Dutch, English, Estonian, Faroese,
 Finnish, French, Galician, German, Greenlandic, Icelandic, Indonesian,
 Irish, Italian, Malay, Norwegian, Portuguese, Spanish, Swedish,
@item @code{ISO-8859-2} for
 Croatian, Czech, Hungarian, Polish, Romanian, Serbian, Slovak, Slovenian,
@item @code{ISO-8859-3} for Maltese,
@item @code{ISO-8859-5} for Macedonian, Serbian,
@item @code{ISO-8859-6} for Arabic,
@item @code{ISO-8859-7} for Greek,
@item @code{ISO-8859-8} for Hebrew,
@item @code{ISO-8859-9} for Turkish,
@item @code{ISO-8859-13} for Latvian, Lithuanian,
@item @code{ISO-8859-15} for
 Basque, Catalan, Dutch, English, Finnish, French, Galician, German, Irish,
 Italian, Portuguese, Spanish, Swedish,
@item @code{KOI8-R} for Russian,
@item @code{KOI8-U} for Ukrainian,
@item @code{CP1251} for Bulgarian, Byelorussian,
@item @code{GB2312}, @code{GBK}, @code{GB18030}
 for simplified writing of Chinese,
@item @code{BIG5}, @code{BIG5-HKSCS}
 for traditional writing of Chinese,
@item @code{EUC-JP} for Japanese,
@item @code{EUC-KR} for Korean,
@item @code{TIS-620} for Thai,
@item @code{UTF-8} for any language, including those listed above.
@end itemize

When single quote characters or double quote characters are used in
translations for your language, and your locale's encoding is one of the
ISO-8859-* charsets, it is best if you create your PO files in UTF-8
encoding, instead of your locale's encoding.  This is because in UTF-8
the real quote characters can be represented (single quote characters:
U+2018, U+2019, double quote characters: U+201C, U+201D), whereas none of
ISO-8859-* charsets has them all.  Users in UTF-8 locales will see the
real quote characters, whereas users in ISO-8859-* locales will see the
vertical apostrophe and the vertical double quote instead (because that's
what the character set conversion will transliterate them to).

To enter such quote characters under X11, you can change your keyboard
mapping using the @code{xmodmap} program.  The X11 names of the quote
characters are "leftsinglequotemark", "rightsinglequotemark",
"leftdoublequotemark", "rightdoublequotemark", "singlelowquotemark",
"doublelowquotemark".

Note that only recent versions of GNU Emacs support the UTF-8 encoding:
Emacs 20 with Mule-UCS, and Emacs 21.  As of January 2001, XEmacs doesn't
support the UTF-8 encoding.

The character encoding name can be written in either upper or lower case.
Usually upper case is preferred.

@item Content-Transfer-Encoding
Set this to @code{8bit}.

@item Plural-Forms
This field is optional.  It is only needed if the PO file has plural forms.
You can find them by searching for the @samp{msgid_plural} keyword.  The
format of the plural forms field is described in @ref{Plural forms}.
@end table

@node Updating, Binaries, Creating, Top
@chapter Updating Existing PO Files

@c FIXME: Rewrite.

@menu
* msgmerge Invocation::         Invoking the @code{msgmerge} Program
* Translated Entries::          Translated Entries
* Fuzzy Entries::               Fuzzy Entries
* Untranslated Entries::        Untranslated Entries
* Obsolete Entries::            Obsolete Entries
* Modifying Translations::      Modifying Translations
* Modifying Comments::          Modifying Comments
* Subedit::                     Mode for Editing Translations
* C Sources Context::           C Sources Context
* Auxiliary::                   Consulting Auxiliary PO Files
* Compendium::                  Using Translation Compendiums
@end menu

@node msgmerge Invocation, Translated Entries, Updating, Updating
@section Invoking the @code{msgmerge} Program

@c FIXME: Rewrite.

@c @example
@c tupdate --help
@c tupdate --version
@c tupdate @var{new} @var{old}
@c @end example

@c File @var{new} is the last created PO file (generally by
@c @code{xgettext}).  It need not contain any translations.  File
@c @var{old} is the PO file including the old translations which will
@c be taken over to the newly created file as long as they still match.

@c When English messages change in the programs, this is reflected in
@c the PO file as extracted by @code{xgettext}.  In large messages, that
@c can be hard to detect, and will obviously result in an incomplete
@c translation.  One of the virtues of @code{tupdate} is that it detects
@c such changes, saving the previous translation into a PO file comment,
@c so marking the entry as obsolete, and giving the modified string with
@c an empty translation, that is, marking the entry as untranslated.

@node Translated Entries, Fuzzy Entries, msgmerge Invocation, Updating
@section Translated Entries

Each PO file entry for which the @code{msgstr} field has been filled with
a translation, and which is not marked as fuzzy (@pxref{Fuzzy Entries}),
is a said to be a @dfn{translated} entry.  Only translated entries will
later be compiled by GNU @code{msgfmt} and become usable in programs.
Other entry types will be excluded; translation will not occur for them.

Some commands are more specifically related to translated entry processing.

@table @kbd
@item t
Find the next translated entry.

@item M-t
Find the previous translated entry.

@end table

The commands @kbd{t} (@code{po-next-translated-entry}) and @kbd{M-t}
(@code{po-previous-transted-entry}) move forwards or backwards, chasing
for an translated entry.  If none is found, the search is extended and
wraps around in the PO file buffer.

Translated entries usually result from the translator having edited in
a translation for them, @ref{Modifying Translations}.  However, if the
variable @code{po-auto-fuzzy-on-edit} is not @code{nil}, the entry having
received a new translation first becomes a fuzzy entry, which ought to
be later unfuzzied before becoming an official, genuine translated entry.
@xref{Fuzzy Entries}.

@node Fuzzy Entries, Untranslated Entries, Translated Entries, Updating
@section Fuzzy Entries

Each PO file entry may have a set of @dfn{attributes}, which are
qualities given a name and explicitely associated with the translation,
using a special system comment.  One of these attributes
has the name @code{fuzzy}, and entries having this attribute are said
to have a fuzzy translation.  They are called fuzzy entries, for short.

Fuzzy entries, even if they account for translated entries for
most other purposes, usually call for revision by the translator.
Those may be produced by applying the program @code{msgmerge} to
update an older translated PO files according to a new PO template
file, when this tool hypothesises that some new @code{msgid} has
been modified only slightly out of an older one, and chooses to pair
what it thinks to be the old translation for the new modified entry.
The slight alteration in the original string (the @code{msgid} string)
should often be reflected in the translated string, and this requires
the intervention of the translator.  For this reason, @code{msgmerge}
might mark some entries as being fuzzy.

Also, the translator may decide herself to mark an entry as fuzzy
for her own convenience, when she wants to remember that the entry
has to be later revisited.  So, some commands are more specifically
related to fuzzy entry processing.

@table @kbd
@item f
Find the next fuzzy entry.

@item M-f
Find the previous fuzzy entry.

@item @key{TAB}
Remove the fuzzy attribute of the current entry.

@end table

The commands @kbd{f} (@code{po-next-fuzzy}) and @kbd{M-f}
(@code{po-previous-fuzzy}) move forwards or backwards, chasing for
a fuzzy entry.  If none is found, the search is extended and wraps
around in the PO file buffer.

The command @kbd{@key{TAB}} (@code{po-unfuzzy}) removes the fuzzy
attribute associated with an entry, usually leaving it translated.
Further, if the variable @code{po-auto-select-on-unfuzzy} has not
the @code{nil} value, the @kbd{@key{TAB}} command will automatically chase
for another interesting entry to work on.  The initial value of
@code{po-auto-select-on-unfuzzy} is @code{nil}.

The initial value of @code{po-auto-fuzzy-on-edit} is @code{nil}.  However,
if the variable @code{po-auto-fuzzy-on-edit} is set to @code{t}, any entry
edited through the @kbd{@key{RET}} command is marked fuzzy, as a way to
ensure some kind of double check, later.  In this case, the usual paradigm
is that an entry becomes fuzzy (if not already) whenever the translator
modifies it.  If she is satisfied with the translation, she then uses
@kbd{@key{TAB}} to pick another entry to work on, clearing the fuzzy attribute
on the same blow.  If she is not satisfied yet, she merely uses @kbd{@key{SPC}}
to chase another entry, leaving the entry fuzzy.

The translator may also use the @kbd{@key{DEL}} command
(@code{po-fade-out-entry}) over any translated entry to mark it as being
fuzzy, when she wants to easily leave a trace she wants to later return
working at this entry.

Also, when time comes to quit working on a PO file buffer with the @kbd{q}
command, the translator is asked for confirmation, if fuzzy string
still exists.

@node Untranslated Entries, Obsolete Entries, Fuzzy Entries, Updating
@section Untranslated Entries

When @code{xgettext} originally creates a PO file, unless told
otherwise, it initializes the @code{msgid} field with the untranslated
string, and leaves the @code{msgstr} string to be empty.  Such entries,
having an empty translation, are said to be @dfn{untranslated} entries.
Later, when the programmer slightly modifies some string right in
the program, this change is later reflected in the PO file
by the appearance of a new untranslated entry for the modified string.

The usual commands moving from entry to entry consider untranslated
entries on the same level as active entries.  Untranslated entries
are easily recognizable by the fact they end with @w{@samp{msgstr ""}}.

The work of the translator might be (quite naively) seen as the process
of seeking for an untranslated entry, editing a translation for
it, and repeating these actions until no untranslated entries remain.
Some commands are more specifically related to untranslated entry
processing.

@table @kbd
@item u
Find the next untranslated entry.

@item M-u
Find the previous untranslated entry.

@item k
Turn the current entry into an untranslated one.

@end table

The commands @kbd{u} (@code{po-next-untranslated-entry}) and @kbd{M-u}
(@code{po-previous-untransted-entry}) move forwards or backwards,
chasing for an untranslated entry.  If none is found, the search is
extended and wraps around in the PO file buffer.

An entry can be turned back into an untranslated entry by
merely emptying its translation, using the command @kbd{k}
(@code{po-kill-msgstr}).  @xref{Modifying Translations}.

Also, when time comes to quit working on a PO file buffer
with the @kbd{q} command, the translator is asked for confirmation,
if some untranslated string still exists.

@node Obsolete Entries, Modifying Translations, Untranslated Entries, Updating
@section Obsolete Entries

By @dfn{obsolete} PO file entries, we mean those entries which are
commented out, usually by @code{msgmerge} when it found that the
translation is not needed anymore by the package being localized.

The usual commands moving from entry to entry consider obsolete
entries on the same level as active entries.  Obsolete entries are
easily recognizable by the fact that all their lines start with
@kbd{#}, even those lines containing @code{msgid} or @code{msgstr}.

Commands exist for emptying the translation or reinitializing it
to the original untranslated string.  Commands interfacing with the
kill ring may force some previously saved text into the translation.
The user may interactively edit the translation.  All these commands
may apply to obsolete entries, carefully leaving the entry obsolete
after the fact.

Moreover, some commands are more specifically related to obsolete
entry processing.

@table @kbd
@item o
Find the next obsolete entry.

@item M-o
Find the previous obsolete entry.

@item @key{DEL}
Make an active entry obsolete, or zap out an obsolete entry.

@end table

The commands @kbd{o} (@code{po-next-obsolete-entry}) and @kbd{M-o}
(@code{po-previous-obsolete-entry}) move forwards or backwards,
chasing for an obsolete entry.  If none is found, the search is
extended and wraps around in the PO file buffer.

PO mode does not provide ways for un-commenting an obsolete entry
and making it active, because this would reintroduce an original
untranslated string which does not correspond to any marked string
in the program sources.  This goes with the philosophy of never
introducing useless @code{msgid} values.

However, it is possible to comment out an active entry, so making
it obsolete.  GNU @code{gettext} utilities will later react to the
disappearance of a translation by using the untranslated string.
The command @kbd{@key{DEL}} (@code{po-fade-out-entry}) pushes the current entry
a little further towards annihilation.  If the entry is active (it is a
translated entry), then it is first made fuzzy.  If it is already fuzzy,
then the entry is merely commented out, with confirmation.  If the entry
is already obsolete, then it is completely deleted from the PO file.
It is easy to recycle the translation so deleted into some other PO file
entry, usually one which is untranslated.  @xref{Modifying Translations}.

Here is a quite interesting problem to solve for later development of
PO mode, for those nights you are not sleepy.  The idea would be that
PO mode might become bright enough, one of these days, to make good
guesses at retrieving the most probable candidate, among all obsolete
entries, for initializing the translation of a newly appeared string.
I think it might be a quite hard problem to do this algorithmically, as
we have to develop good and efficient measures of string similarity.
Right now, PO mode completely lets the decision to the translator,
when the time comes to find the adequate obsolete translation, it
merely tries to provide handy tools for helping her to do so.

@node Modifying Translations, Modifying Comments, Obsolete Entries, Updating
@section Modifying Translations

PO mode prevents direct edition of the PO file, by the usual
means Emacs give for altering a buffer's contents.  By doing so,
it pretends helping the translator to avoid little clerical errors
about the overall file format, or the proper quoting of strings,
as those errors would be easily made.  Other kinds of errors are
still possible, but some may be caught and diagnosed by the batch
validation process, which the translator may always trigger by the
@kbd{V} command.  For all other errors, the translator has to rely on
her own judgment, and also on the linguistic reports submitted to her
by the users of the translated package, having the same mother tongue.

When the time comes to create a translation, correct an error diagnosed
mechanically or reported by a user, the translators have to resort to
using the following commands for modifying the translations.

@table @kbd
@item @key{RET}
Interactively edit the translation.

@item @key{LFD}
Reinitialize the translation with the original, untranslated string.

@item k
Save the translation on the kill ring, and delete it.

@item w
Save the translation on the kill ring, without deleting it.

@item y
Replace the translation, taking the new from the kill ring.

@end table

The command @kbd{@key{RET}} (@code{po-edit-msgstr}) opens a new Emacs
window meant to edit in a new translation, or to modify an already existing
translation.  The new window contains a copy of the translation taken from
the current PO file entry, all ready for edition, expunged of all quoting
marks, fully modifiable and with the complete extent of Emacs modifying
commands.  When the translator is done with her modifications, she may use
@w{@kbd{C-c C-c}} to close the subedit window with the automatically requoted
results, or @w{@kbd{C-c C-k}} to abort her modifications.  @xref{Subedit},
for more information.

The command @kbd{@key{LFD}} (@code{po-msgid-to-msgstr}) initializes, or
reinitializes the translation with the original string.  This command is
normally used when the translator wants to redo a fresh translation of
the original string, disregarding any previous work.

It is possible to arrange so, whenever editing an untranslated
entry, the @kbd{@key{LFD}} command be automatically executed.  If you set
@code{po-auto-edit-with-msgid} to @code{t}, the translation gets
initialised with the original string, in case none exists already.
The default value for @code{po-auto-edit-with-msgid} is @code{nil}.

In fact, whether it is best to start a translation with an empty
string, or rather with a copy of the original string, is a matter of
taste or habit.  Sometimes, the source language and the
target language are so different that is simply best to start writing
on an empty page.  At other times, the source and target languages
are so close that it would be a waste to retype a number of words
already being written in the original string.  A translator may also
like having the original string right under her eyes, as she will
progressively overwrite the original text with the translation, even
if this requires some extra editing work to get rid of the original.

The command @kbd{k} (@code{po-kill-msgstr}) merely empties the
translation string, so turning the entry into an untranslated
one.  But while doing so, its previous contents is put apart in
a special place, known as the kill ring.  The command @kbd{w}
(@code{po-kill-ring-save-msgstr}) has also the effect of taking a
copy of the translation onto the kill ring, but it otherwise leaves
the entry alone, and does @emph{not} remove the translation from the
entry.  Both commands use exactly the Emacs kill ring, which is shared
between buffers, and which is well known already to Emacs lovers.

The translator may use @kbd{k} or @kbd{w} many times in the course
of her work, as the kill ring may hold several saved translations.
From the kill ring, strings may later be reinserted in various
Emacs buffers.  In particular, the kill ring may be used for moving
translation strings between different entries of a single PO file
buffer, or if the translator is handling many such buffers at once,
even between PO files.

To facilitate exchanges with buffers which are not in PO mode, the
translation string put on the kill ring by the @kbd{k} command is fully
unquoted before being saved: external quotes are removed, multi-line
strings are concatenated, and backslash escaped sequences are turned
into their corresponding characters.  In the special case of obsolete
entries, the translation is also uncommented prior to saving.

The command @kbd{y} (@code{po-yank-msgstr}) completely replaces the
translation of the current entry by a string taken from the kill ring.
Following Emacs terminology, we then say that the replacement
string is @dfn{yanked} into the PO file buffer.
@xref{Yanking, , , emacs, The Emacs Editor}.
The first time @kbd{y} is used, the translation receives the value of
the most recent addition to the kill ring.  If @kbd{y} is typed once
again, immediately, without intervening keystrokes, the translation
just inserted is taken away and replaced by the second most recent
addition to the kill ring.  By repeating @kbd{y} many times in a row,
the translator may travel along the kill ring for saved strings,
until she finds the string she really wanted.

When a string is yanked into a PO file entry, it is fully and
automatically requoted for complying with the format PO files should
have.  Further, if the entry is obsolete, PO mode then appropriately
push the inserted string inside comments.  Once again, translators
should not burden themselves with quoting considerations besides, of
course, the necessity of the translated string itself respective to
the program using it.

Note that @kbd{k} or @kbd{w} are not the only commands pushing strings
on the kill ring, as almost any PO mode command replacing translation
strings (or the translator comments) automatically saves the old string
on the kill ring.  The main exceptions to this general rule are the
yanking commands themselves.

To better illustrate the operation of killing and yanking, let's
use an actual example, taken from a common situation.  When the
programmer slightly modifies some string right in the program, his
change is later reflected in the PO file by the appearance
of a new untranslated entry for the modified string, and the fact
that the entry translating the original or unmodified string becomes
obsolete.  In many cases, the translator might spare herself some work
by retrieving the unmodified translation from the obsolete entry,
then initializing the untranslated entry @code{msgstr} field with
this retrieved translation.  Once this done, the obsolete entry is
not wanted anymore, and may be safely deleted.

When the translator finds an untranslated entry and suspects that a
slight variant of the translation exists, she immediately uses @kbd{m}
to mark the current entry location, then starts chasing obsolete
entries with @kbd{o}, hoping to find some translation corresponding
to the unmodified string.  Once found, she uses the @kbd{@key{DEL}} command
for deleting the obsolete entry, knowing that @kbd{@key{DEL}} also @emph{kills}
the translation, that is, pushes the translation on the kill ring.
Then, @kbd{r} returns to the initial untranslated entry, and @kbd{y}
then @emph{yanks} the saved translation right into the @code{msgstr}
field.  The translator is then free to use @kbd{@key{RET}} for fine
tuning the translation contents, and maybe to later use @kbd{u},
then @kbd{m} again, for going on with the next untranslated string.

When some sequence of keys has to be typed over and over again, the
translator may find it useful to become better acquainted with the Emacs
capability of learning these sequences and playing them back under request.
@xref{Keyboard Macros, , , emacs, The Emacs Editor}.

@node Modifying Comments, Subedit, Modifying Translations, Updating
@section Modifying Comments

Any translation work done seriously will raise many linguistic
difficulties, for which decisions have to be made, and the choices
further documented.  These documents may be saved within the
PO file in form of translator comments, which the translator
is free to create, delete, or modify at will.  These comments may
be useful to herself when she returns to this PO file after a while.

Comments not having whitespace after the initial @samp{#}, for example,
those beginning with @samp{#.} or @samp{#:}, are @emph{not} translator
comments, they are exclusively created by other @code{gettext} tools.
So, the commands below will never alter such system added comments,
they are not meant for the translator to modify.  @xref{PO Files}.

The following commands are somewhat similar to those modifying translations,
so the general indications given for those apply here.  @xref{Modifying
Translations}.

@table @kbd

@item #
Interactively edit the translator comments.

@item K
Save the translator comments on the kill ring, and delete it.

@item W
Save the translator comments on the kill ring, without deleting it.

@item Y
Replace the translator comments, taking the new from the kill ring.

@end table

These commands parallel PO mode commands for modifying the translation
strings, and behave much the same way as they do, except that they handle
this part of PO file comments meant for translator usage, rather
than the translation strings.  So, if the descriptions given below are
slightly succinct, it is because the full details have already been given.
@xref{Modifying Translations}.

The command @kbd{#} (@code{po-edit-comment}) opens a new Emacs window
containing a copy of the translator comments on the current PO file entry.
If there are no such comments, PO mode understands that the translator wants
to add a comment to the entry, and she is presented with an empty screen.
Comment marks (@kbd{#}) and the space following them are automatically
removed before edition, and reinstated after.  For translator comments
pertaining to obsolete entries, the uncommenting and recommenting operations
are done twice.  Once in the editing window, the keys @w{@kbd{C-c C-c}}
allow the translator to tell she is finished with editing the comment.
@xref{Subedit}, for further details.

Functions found on @code{po-subedit-mode-hook}, if any, are executed after
the string has been inserted in the edit buffer.

The command @kbd{K} (@code{po-kill-comment}) gets rid of all
translator comments, while saving those comments on the kill ring.
The command @kbd{W} (@code{po-kill-ring-save-comment}) takes
a copy of the translator comments on the kill ring, but leaves
them undisturbed in the current entry.  The command @kbd{Y}
(@code{po-yank-comment}) completely replaces the translator comments
by a string taken at the front of the kill ring.  When this command
is immediately repeated, the comments just inserted are withdrawn,
and replaced by other strings taken along the kill ring.

On the kill ring, all strings have the same nature.  There is no
distinction between @emph{translation} strings and @emph{translator
comments} strings.  So, for example, let's presume the translator
has just finished editing a translation, and wants to create a new
translator comment to document why the previous translation was
not good, just to remember what was the problem.  Foreseeing that she
will do that in her documentation, the translator may want to quote
the previous translation in her translator comments.  To do so, she
may initialize the translator comments with the previous translation,
still at the head of the kill ring.  Because editing already pushed the
previous translation on the kill ring, she merely has to type @kbd{M-w}
prior to @kbd{#}, and the previous translation will be right there,
all ready for being introduced by some explanatory text.

On the other hand, presume there are some translator comments already
and that the translator wants to add to those comments, instead
of wholly replacing them.  Then, she should edit the comment right
away with @kbd{#}.  Once inside the editing window, she can use the
regular Emacs commands @kbd{C-y} (@code{yank}) and @kbd{M-y}
(@code{yank-pop}) to get the previous translation where she likes.

@node Subedit, C Sources Context, Modifying Comments, Updating
@section Details of Sub Edition

The PO subedit minor mode has a few peculiarities worth being described
in fuller detail.  It installs a few commands over the usual editing set
of Emacs, which are described below.

@table @kbd
@item C-c C-c
Complete edition.

@item C-c C-k
Abort edition.

@item C-c C-a
Consult auxiliary PO files.

@end table

The window's contents represents a translation for a given message,
or a translator comment.  The translator may modify this window to
her heart's content.  Once this done, the command @w{@kbd{C-c C-c}}
(@code{po-subedit-exit}) may be used to return the edited translation into
the PO file, replacing the original translation, even if it moved out of
sight or if buffers were switched.

If the translator becomes unsatisfied with her translation or comment,
to the extent she prefers keeping what was existent prior to the
@kbd{@key{RET}} or @kbd{#} command, she may use the command @w{@kbd{C-c C-k}}
(@code{po-subedit-abort}) to merely get rid of edition, while preserving
the original translation or comment.  Another way would be for her to exit
normally with @w{@kbd{C-c C-c}}, then type @code{U} once for undoing the
whole effect of last edition.

The command @w{@kbd{C-c C-a}} allows for glancing through translations
already achieved in other languages, directly while editing the current
translation.  This may be quite convenient when the translator is fluent
at many languages, but of course, only makes sense when such completed
auxiliary PO files are already available to her (@pxref{Auxiliary}).

Functions found on @code{po-subedit-mode-hook}, if any, are executed after
the string has been inserted in the edit buffer.

While editing her translation, the translator should pay attention to not
inserting unwanted @kbd{@key{RET}} (newline) characters at the end of
the translated string if those are not meant to be there, or to removing
such characters when they are required.  Since these characters are not
visible in the editing buffer, they are easily introduced by mistake.
To help her, @kbd{@key{RET}} automatically puts the character @kbd{<}
at the end of the string being edited, but this @kbd{<} is not really
part of the string.  On exiting the editing window with @w{@kbd{C-c C-c}},
PO mode automatically removes such @kbd{<} and all whitespace added after
it.  If the translator adds characters after the terminating @kbd{<}, it
looses its delimiting property and integrally becomes part of the string.
If she removes the delimiting @kbd{<}, then the edited string is taken
@emph{as is}, with all trailing newlines, even if invisible.  Also, if
the translated string ought to end itself with a genuine @kbd{<}, then
the delimiting @kbd{<} may not be removed; so the string should appear,
in the editing window, as ending with two @kbd{<} in a row.

When a translation (or a comment) is being edited, the translator may move
the cursor back into the PO file buffer and freely move to other entries,
browsing at will.  If, with an edition pending, the translator wanders in the
PO file buffer, she may decide to start modifying another entry.  Each entry
being edited has its own subedit buffer.  It is possible to simultaneously
edit the translation @emph{and} the comment of a single entry, or to
edit entries in different PO files, all at once.  Typing @kbd{@key{RET}}
on a field already being edited merely resumes that particular edit.  Yet,
the translator should better be comfortable at handling many Emacs windows!

Pending subedits may be completed or aborted in any order, regardless
of how or when they were started.  When many subedits are pending and the
translator asks for quitting the PO file (with the @kbd{q} command), subedits
are automatically resumed one at a time, so she may decide for each of them.

@node C Sources Context, Auxiliary, Subedit, Updating
@section C Sources Context

PO mode is particularily powerful when used with PO files
created through GNU @code{gettext} utilities, as those utilities
insert special comments in the PO files they generate.
Some of these special comments relate the PO file entry to
exactly where the untranslated string appears in the program sources.

When the translator gets to an untranslated entry, she is fairly
often faced with an original string which is not as informative as
it normally should be, being succinct, cryptic, or otherwise ambiguous.
Before chosing how to translate the string, she needs to understand
better what the string really means and how tight the translation has
to be.  Most of times, when problems arise, the only way left to make
her judgment is looking at the true program sources from where this
string originated, searching for surrounding comments the programmer
might have put in there, and looking around for helping clues of
@emph{any} kind.

Surely, when looking at program sources, the translator will receive
more help if she is a fluent programmer.  However, even if she is
not versed in programming and feels a little lost in C code, the
translator should not be shy at taking a look, once in a while.
It is most probable that she will still be able to find some of the
hints she needs.  She will learn quickly to not feel uncomfortable
in program code, paying more attention to programmer's comments,
variable and function names (if he dared chosing them well), and
overall organization, than to programmation itself.

The following commands are meant to help the translator at getting
program source context for a PO file entry.

@table @kbd
@item s
Resume the display of a program source context, or cycle through them.

@item M-s
Display of a program source context selected by menu.

@item S
Add a directory to the search path for source files.

@item M-S
Delete a directory from the search path for source files.

@end table

The commands @kbd{s} (@code{po-cycle-reference}) and @kbd{M-s}
(@code{po-select-source-reference}) both open another window displaying
some source program file, and already positioned in such a way that
it shows an actual use of the string to be translated.  By doing
so, the command gives source program context for the string.  But if
the entry has no source context references, or if all references
are unresolved along the search path for program sources, then the
command diagnoses this as an error.

Even if @kbd{s} (or @kbd{M-s}) opens a new window, the cursor stays
in the PO file window.  If the translator really wants to
get into the program source window, she ought to do it explicitly,
maybe by using command @kbd{O}.

When @kbd{s} is typed for the first time, or for a PO file entry which
is different of the last one used for getting source context, then the
command reacts by giving the first context available for this entry,
if any.  If some context has already been recently displayed for the
current PO file entry, and the translator wandered off to do other
things, typing @kbd{s} again will merely resume, in another window,
the context last displayed.  In particular, if the translator moved
the cursor away from the context in the source file, the command will
bring the cursor back to the context.  By using @kbd{s} many times
in a row, with no other commands intervening, PO mode will cycle to
the next available contexts for this particular entry, getting back
to the first context once the last has been shown.

The command @kbd{M-s} behaves differently.  Instead of cycling through
references, it lets the translator choose a particular reference among
many, and displays that reference.  It is best used with completion,
if the translator types @kbd{@key{TAB}} immediately after @kbd{M-s}, in
response to the question, she will be offered a menu of all possible
references, as a reminder of which are the acceptable answers.
This command is useful only where there are really many contexts
available for a single string to translate.

Program source files are usually found relative to where the PO
file stands.  As a special provision, when this fails, the file is
also looked for, but relative to the directory immediately above it.
Those two cases take proper care of most PO files.  However, it might
happen that a PO file has been moved, or is edited in a different
place than its normal location.  When this happens, the translator
should tell PO mode in which directory normally sits the genuine PO
file.  Many such directories may be specified, and all together, they
constitute what is called the @dfn{search path} for program sources.
The command @kbd{S} (@code{po-consider-source-path}) is used to interactively
enter a new directory at the front of the search path, and the command
@kbd{M-S} (@code{po-ignore-source-path}) is used to select, with completion,
one of the directories she does not want anymore on the search path.

@node Auxiliary, Compendium, C Sources Context, Updating
@section Consulting Auxiliary PO Files

PO mode is able to help the knowledgeable translator, being fluent in
many languages, at taking advantage of translations already achieved
in other languages she just happens to know.  It provides these other
language translations as additional context for her own work.  Moreover,
it has features to ease the production of translations for many languages
at once, for translators preferring to work in this way.

An @dfn{auxiliary} PO file is an existing PO file meant for the same
package the translator is working on, but targeted to a different mother
tongue language.  Commands exist for declaring and handling auxiliary
PO files, and also for showing contexts for the entry under work.

Here are the auxiliary file commands available in PO mode.

@table @kbd
@item a
Seek auxiliary files for another translation for the same entry.

@item M-a
Switch to a particular auxiliary file.

@item A
Declare this PO file as an auxiliary file.

@item M-A
Remove this PO file from the list of auxiliary files.

@end table

Command @kbd{A} (@code{po-consider-as-auxiliary}) adds the current
PO file to the list of auxiliary files, while command @kbd{M-A}
(@code{po-ignore-as-auxiliary} just removes it.

The command @kbd{a} (@code{po-cycle-auxiliary}) seeks all auxiliary PO
files, round-robin, searching for a translated entry in some other language
having an @code{msgid} field identical as the one for the current entry.
The found PO file, if any, takes the place of the current PO file in
the display (its window gets on top).  Before doing so, the current PO
file is also made into an auxiliary file, if not already.  So, @kbd{a}
in this newly displayed PO file will seek another PO file, and so on,
so repeating @kbd{a} will eventually yield back the original PO file.

The command @kbd{M-a} (@code{po-select-auxiliary}) asks the translator
for her choice of a particular auxiliary file, with completion, and
then switches to that selected PO file.  The command also checks if
the selected file has an @code{msgid} field identical as the one for
the current entry, and if yes, this entry becomes current.  Otherwise,
the cursor of the selected file is left undisturbed.

For all this to work fully, auxiliary PO files will have to be normalized,
in that way that @code{msgid} fields should be written @emph{exactly}
the same way.  It is possible to write @code{msgid} fields in various
ways for representing the same string, different writing would break the
proper behaviour of the auxiliary file commands of PO mode.  This is not
expected to be much a problem in practice, as most existing PO files have
their @code{msgid} entries written by the same GNU @code{gettext} tools.

However, PO files initially created by PO mode itself, while marking
strings in source files, are normalised differently.  So are PO
files resulting of the the @samp{M-x normalize} command.  Until these
discrepancies between PO mode and other GNU @code{gettext} tools get
fully resolved, the translator should stay aware of normalisation issues.

@node Compendium,  , Auxiliary, Updating
@section Using Translation Compendiums

@c FIXME: Rewrite.

Compendiums are yet to be implemented.

An incoming PO mode feature will let the translator maintain a
compendium of already achieved translations.  A @dfn{compendium}
is a special PO file containing a set of translations recurring in
many different packages.  The translator will be given commands for
adding entries to her compendium, and later initializing untranslated
entries, or updating already translated entries, from translations
kept in the compendium.  For this to work, however, the compendium
would have to be normalized.  @xref{Normalizing}.

@c It is not useful that I modify the @file{lib/} routines if not done in
@c the true sources.  How do you/I/they proceed for getting this job done?
@c I presume that @file{lib/} routines will all use @code{gettext} for
@c the time being.

@node Binaries, Users, Updating, Top
@chapter Producing Binary MO Files

@c FIXME: Rewrite.

@menu
* msgfmt Invocation::           Invoking the @code{msgfmt} Program
* MO Files::                    The Format of GNU MO Files
@end menu

@node msgfmt Invocation, MO Files, Binaries, Binaries
@section Invoking the @code{msgfmt} Program

@c FIXME: Rewrite.

@example
Usage: msgfmt [@var{option}] @var{filename}.po @dots{}
@end example

@table @samp
@item -a @var{number}
@itemx --alignment=@var{number}
Align strings to @var{number} bytes (default: 1).
@c Currently the README mentions that this constant could be changed by
@c the installer by changing the value in config.h.  Should this go away?

@item -h
@itemx --help
Display this help and exit.

@item --no-hash
Binary file will not include the hash table.

@item -o @var{file}
@itemx --output-file=@var{file}
Specify output file name as @var{file}.

@itemx --strict
Direct the program to work strictly following the Uniforum/Sun
implementation.  Currently this only affects the naming of the output
file.  If this option is not given the name of the output file is the
same as the domain name.  If the strict Uniforum mode is enabled the
suffix @file{.mo} is added to the file name if it is not already
present.

We find this behaviour of Sun's implementation rather silly and so by
default this mode is @emph{not} selected.

@item -v
@itemx --verbose
Detect and diagnose input file anomalies which might represent
translation errors.  The @code{msgid} and @code{msgstr} strings are
studied and compared.  It is considered abnormal that one string
starts or ends with a newline while the other does not.

Also, if the string represents a format string used in a
@code{printf}-like function both strings should have the same number of
@samp{%} format specifiers, with matching types.  If the flag
@code{c-format} or @code{possible-c-format} appears in the special
comment @key{#,} for this entry a check is performed.  For example, the
check will diagnose using @samp{%.*s} against @samp{%s}, or @samp{%d}
against @samp{%s}, or @samp{%d} against @samp{%x}.  It can even handle
positional parameters.

Normally the @code{xgettext} program automatically decides whether a
string is a format string or not.  This algorithm is not perfect,
though.  It might regard a string as a format string though it is not
used in a @code{printf}-like function and so @code{msgfmt} might report
errors where there are none.  Or the other way round: a string is not
regarded as a format string but it is used in a @code{printf}-like
function.

So solve this problem the programmer can dictate the decision to the
@code{xgettext} program (@pxref{c-format}).  The translator should not
consider removing the flag from the @key{#,} line.  This "fix" would be
reversed again as soon as @code{msgmerge} is called the next time.

@item -V
@itemx --version
Output version information and exit.

@end table

If input file is @samp{-}, standard input is read.  If output file
is @samp{-}, output is written to standard output.

@node MO Files,  , msgfmt Invocation, Binaries
@section The Format of GNU MO Files

The format of the generated MO files is best described by a picture,
which appears below.

The first two words serve the identification of the file.  The magic
number will always signal GNU MO files.  The number is stored in the
byte order of the generating machine, so the magic number really is
two numbers: @code{0x950412de} and @code{0xde120495}.  The second
word describes the current revision of the file format.  For now the
revision is 0.  This might change in future versions, and ensures
that the readers of MO files can distinguish new formats from old
ones, so that both can be handled correctly.  The version is kept
separate from the magic number, instead of using different magic
numbers for different formats, mainly because @file{/etc/magic} is
not updated often.  It might be better to have magic separated from
internal format version identification.

Follow a number of pointers to later tables in the file, allowing
for the extension of the prefix part of MO files without having to
recompile programs reading them.  This might become useful for later
inserting a few flag bits, indication about the charset used, new
tables, or other things.

Then, at offset @var{O} and offset @var{T} in the picture, two tables
of string descriptors can be found.  In both tables, each string
descriptor uses two 32 bits integers, one for the string length,
another for the offset of the string in the MO file, counting in bytes
from the start of the file.  The first table contains descriptors
for the original strings, and is sorted so the original strings
are in increasing lexicographical order.  The second table contains
descriptors for the translated strings, and is parallel to the first
table: to find the corresponding translation one has to access the
array slot in the second array with the same index.

Having the original strings sorted enables the use of simple binary
search, for when the MO file does not contain an hashing table, or
for when it is not practical to use the hashing table provided in
the MO file.  This also has another advantage, as the empty string
in a PO file GNU @code{gettext} is usually @emph{translated} into
some system information attached to that particular MO file, and the
empty string necessarily becomes the first in both the original and
translated tables, making the system information very easy to find.

The size @var{S} of the hash table can be zero.  In this case, the
hash table itself is not contained in the MO file.  Some people might
prefer this because a precomputed hashing table takes disk space, and
does not win @emph{that} much speed.  The hash table contains indices
to the sorted array of strings in the MO file.  Conflict resolution is
done by double hashing.  The precise hashing algorithm used is fairly
dependent of GNU @code{gettext} code, and is not documented here.

As for the strings themselves, they follow the hash file, and each
is terminated with a @key{NUL}, and this @key{NUL} is not counted in
the length which appears in the string descriptor.  The @code{msgfmt}
program has an option selecting the alignment for MO file strings.
With this option, each string is separately aligned so it starts at
an offset which is a multiple of the alignment value.  On some RISC
machines, a correct alignment will speed things up.

Plural forms are stored by letting the plural of the original string
follow the singular of the original string, separated through a
@key{NUL} byte.  The length which appears in the string descriptor
includes both.  However, only the singular of the original string
takes part in the hash table lookup.  The plural variants of the
translation are all stored consecutively, separated through a
@key{NUL} byte.  Here also, the length in the string descriptor
includes all of them.

Nothing prevents a MO file from having embedded @key{NUL}s in strings.
However, the program interface currently used already presumes
that strings are @key{NUL} terminated, so embedded @key{NUL}s are
somewhat useless.  But the MO file format is general enough so other
interfaces would be later possible, if for example, we ever want to
implement wide characters right in MO files, where @key{NUL} bytes may
accidently appear.  (No, we don't want to have wide characters in MO
files.  They would make the file unnecessarily large, and the
@samp{wchar_t} type being platform dependent, MO files would be
platform dependent as well.)

This particular issue has been strongly debated in the GNU
@code{gettext} development forum, and it is expectable that MO file
format will evolve or change over time.  It is even possible that many
formats may later be supported concurrently.  But surely, we have to
start somewhere, and the MO file format described here is a good start.
Nothing is cast in concrete, and the format may later evolve fairly
easily, so we should feel comfortable with the current approach.

@example
@group
        byte
             +------------------------------------------+
          0  | magic number = 0x950412de                |
             |                                          |
          4  | file format revision = 0                 |
             |                                          |
          8  | number of strings                        |  == N
             |                                          |
         12  | offset of table with original strings    |  == O
             |                                          |
         16  | offset of table with translation strings |  == T
             |                                          |
         20  | size of hashing table                    |  == S
             |                                          |
         24  | offset of hashing table                  |  == H
             |                                          |
             .                                          .
             .    (possibly more entries later)         .
             .                                          .
             |                                          |
          O  | length & offset 0th string  ----------------.
      O + 8  | length & offset 1st string  ------------------.
              ...                                    ...   | |
O + ((N-1)*8)| length & offset (N-1)th string           |  | |
             |                                          |  | |
          T  | length & offset 0th translation  ---------------.
      T + 8  | length & offset 1st translation  -----------------.
              ...                                    ...   | | | |
T + ((N-1)*8)| length & offset (N-1)th translation      |  | | | |
             |                                          |  | | | |
          H  | start hash table                         |  | | | |
              ...                                    ...   | | | |
  H + S * 4  | end hash table                           |  | | | |
             |                                          |  | | | |
             | NUL terminated 0th string  <----------------' | | |
             |                                          |    | | |
             | NUL terminated 1st string  <------------------' | |
             |                                          |      | |
              ...                                    ...       | |
             |                                          |      | |
             | NUL terminated 0th translation  <---------------' |
             |                                          |        |
             | NUL terminated 1st translation  <-----------------'
             |                                          |
              ...                                    ...
             |                                          |
             +------------------------------------------+
@end group
@end example

@node Users, Programmers, Binaries, Top
@chapter The User's View

When GNU @code{gettext} will truly have reached its goal, average users
should feel some kind of astonished pleasure, seeing the effect of
that strange kind of magic that just makes their own native language
appear everywhere on their screens.  As for naive users, they would
ideally have no special pleasure about it, merely taking their own
language for @emph{granted}, and becoming rather unhappy otherwise.

So, let's try to describe here how we would like the magic to operate,
as we want the users' view to be the simplest, among all ways one
could look at GNU @code{gettext}.  All other software engineers:
programmers, translators, maintainers, should work together in such a
way that the magic becomes possible.  This is a long and progressive
undertaking, and information is available about the progress of the
Translation Project.

When a package is distributed, there are two kinds of users:
@dfn{installers} who fetch the distribution, unpack it, configure
it, compile it and install it for themselves or others to use; and
@dfn{end users} that call programs of the package, once these have
been installed at their site.  GNU @code{gettext} is offering magic
for both installers and end users.

@menu
* Matrix::                      The Current @file{ABOUT-NLS} Matrix
* Installers::                  Magic for Installers
* End Users::                   Magic for End Users
@end menu

@node Matrix, Installers, Users, Users
@section The Current @file{ABOUT-NLS} Matrix

Languages are not equally supported in all packages using GNU
@code{gettext}.  To know if some package uses GNU @code{gettext}, one
may check the distribution for the @file{ABOUT-NLS} information file, for
some @file{@var{ll}.po} files, often kept together into some @file{po/}
directory, or for an @file{intl/} directory.  Internationalized packages
have usually many @file{@var{ll}.po} files, where @var{ll} represents
the language.  @ref{End Users} for a complete description of the format
for @var{ll}.

More generally, a matrix is available for showing the current state
of the Translation Project, listing which packages are prepared for
multi-lingual messages, and which languages are supported by each.
Because this information changes often, this matrix is not kept within
this GNU @code{gettext} manual.  This information is often found in
file @file{ABOUT-NLS} from various distributions, but is also as old as
the distribution itself.  A recent copy of this @file{ABOUT-NLS} file,
containing up-to-date information, should generally be found on the
Translation Project sites, and also on most GNU archive sites.

@node Installers, End Users, Matrix, Users
@section Magic for Installers

By default, packages fully using GNU @code{gettext}, internally,
are installed in such a way that they to allow translation of
messages.  At @emph{configuration} time, those packages should
automatically detect whether the underlying host system already provides
the GNU @code{gettext} functions.  If not,
the GNU @code{gettext} library should be automatically prepared
and used.  Installers may use special options at configuration
time for changing this behavior.  The command @samp{./configure
--with-included-gettext} bypasses system @code{gettext} to
use the included GNU @code{gettext} instead,
while @samp{./configure --disable-nls}
produces programs totally unable to translate messages.

Internationalized packages have usually many @file{@var{ll}.po}
files.  Unless
translations are disabled, all those available are installed together
with the package.  However, the environment variable @code{LINGUAS}
may be set, prior to configuration, to limit the installed set.
@code{LINGUAS} should then contain a space separated list of two-letter
codes, stating which languages are allowed.

@node End Users,  , Installers, Users
@section Magic for End Users

We consider here those packages using GNU @code{gettext} internally,
and for which the installers did not disable translation at
@emph{configure} time.  Then, users only have to set the @code{LANG}
environment variable to the appropriate @samp{@var{ll}_@var{CC}}
combination prior to using the programs in the package.  @xref{Matrix}.
For example, let's presume a German site.  At the shell prompt, users
merely have to execute @w{@samp{setenv LANG de_DE}} (in @code{csh}) or
@w{@samp{export LANG; LANG=de_DE}} (in @code{sh}).  They could even do
this from their @file{.login} or @file{.profile} file.

@node Programmers, Translators, Users, Top
@chapter The Programmer's View

@c FIXME: Reorganize whole chapter.

One aim of the current message catalog implementation provided by
GNU @code{gettext} was to use the systems message catalog handling, if the
installer wishes to do so.  So we perhaps should first take a look at
the solutions we know about.  The people in the POSIX committee did not
manage to agree on one of the semi-official standards which we'll
describe below.  In fact they couldn't agree on anything, so they decided
only to include an example of an interface.  The major Unix vendors
are split in the usage of the two most important specifications: X/Open's
catgets vs. Uniforum's gettext interface.  We'll describe them both and
later explain our solution of this dilemma.

@menu
* catgets::                     About @code{catgets}
* gettext::                     About @code{gettext}
* Comparison::                  Comparing the two interfaces
* Using libintl.a::             Using libintl.a in own programs
* gettext grok::                Being a @code{gettext} grok
* Temp Programmers::            Temporary Notes for the Programmers Chapter
@end menu

@node catgets, gettext, Programmers, Programmers
@section About @code{catgets}

The @code{catgets} implementation is defined in the X/Open Portability
Guide, Volume 3, XSI Supplementary Definitions, Chapter 5.  But the
process of creating this standard seemed to be too slow for some of
the Unix vendors so they created their implementations on preliminary
versions of the standard.  Of course this leads again to problems while
writing platform independent programs: even the usage of @code{catgets}
does not guarantee a unique interface.

Another, personal comment on this that only a bunch of committee members
could have made this interface.  They never really tried to program
using this interface.  It is a fast, memory-saving implementation, an
user can happily live with it.  But programmers hate it (at least me and
some others do@dots{})

But we must not forget one point: after all the trouble with transfering
the rights on Unix(tm) they at last came to X/Open, the very same who
published this specification.  This leads me to making the prediction
that this interface will be in future Unix standards (e.g. Spec1170) and
therefore part of all Unix implementation (implementations, which are
@emph{allowed} to wear this name).

@menu
* Interface to catgets::        The interface
* Problems with catgets::       Problems with the @code{catgets} interface?!
@end menu

@node Interface to catgets, Problems with catgets, catgets, catgets
@subsection The Interface

The interface to the @code{catgets} implementation consists of three
functions which correspond to those used in file access: @code{catopen}
to open the catalog for using, @code{catgets} for accessing the message
tables, and @code{catclose} for closing after work is done.  Prototypes
for the functions and the needed definitions are in the
@code{<nl_types.h>} header file.

@code{catopen} is used like in this:

@example
nl_catd catd = catopen ("catalog_name", 0);
@end example

The function takes as the argument the name of the catalog.  This usual
refers to the name of the program or the package.  The second parameter
is not further specified in the standard.  I don't even know whether it
is implemented consistently among various systems.  So the common advice
is to use @code{0} as the value.  The return value is a handle to the
message catalog, equivalent to handles to file returned by @code{open}.

This handle is of course used in the @code{catgets} function which can
be used like this:

@example
char *translation = catgets (catd, set_no, msg_id, "original string");
@end example

The first parameter is this catalog descriptor.  The second parameter
specifies the set of messages in this catalog, in which the message
described by @code{msg_id} is obtained.  @code{catgets} therefore uses a
three-stage addressing:

@display
catalog name @result{} set number @result{} message ID @result{} translation
@end display

@c Anybody else loving Haskell??? :-) -- Uli

The fourth argument is not used to address the translation.  It is given
as a default value in case when one of the addressing stages fail.  One
important thing to remember is that although the return type of catgets
is @code{char *} the resulting string @emph{must not} be changed.  It
should better be @code{const char *}, but the standard is published in
1988, one year before ANSI C.

@noindent
The last of these function functions is used and behaves as expected:

@example
catclose (catd);
@end example

After this no @code{catgets} call using the descriptor is legal anymore.

@node Problems with catgets,  , Interface to catgets, catgets
@subsection Problems with the @code{catgets} Interface?!

Now that this description seemed to be really easy --- where are the
problem we speak of?  In fact the interface could be used in a
reasonable way, but constructing the message catalogs is a pain.  The
reason for this lies in the third argument of @code{catgets}: the unique
message ID.  This has to be a numeric value for all messages in a single
set.  Perhaps you could imagine the problems keeping such a list while
changing the source code.  Add a new message here, remove one there.  Of
course there have been developed a lot of tools helping to organize this
chaos but one as the other fails in one aspect or the other.  We don't
want to say that the other approach has no problems but they are far
more easy to manage.

@node gettext, Comparison, catgets, Programmers
@section About @code{gettext}

The definition of the @code{gettext} interface comes from a Uniforum
proposal and it is followed by at least one major Unix vendor
(Sun) in its last developments.  It is not specified in any official
standard, though.

The main points about this solution is that it does not follow the
method of normal file handling (open-use-close) and that it does not
burden the programmer so many task, especially the unique key handling.
Of course here is also a unique key needed, but this key is the message
itself (how long or short it is).  See @ref{Comparison} for a more
detailed comparison of the two methods.

The following section contains a rather detailed description of the
interface.  We make it that detailed because this is the interface
we chose for the GNU @code{gettext} Library.  Programmers interested
in using this library will be interested in this description.

@menu
* Interface to gettext::        The interface
* Ambiguities::                 Solving ambiguities
* Locating Catalogs::           Locating message catalog files
* Charset conversion::          How to request conversion to Unicode
* Plural forms::                Additional functions for handling plurals
* GUI program problems::        Another technique for solving ambiguities
* Optimized gettext::           Optimization of the *gettext functions
@end menu

@node Interface to gettext, Ambiguities, gettext, gettext
@subsection The Interface

The minimal functionality an interface must have is a) to select a
domain the strings are coming from (a single domain for all programs is
not reasonable because its construction and maintenance is difficult,
perhaps impossible) and b) to access a string in a selected domain.

This is principally the description of the @code{gettext} interface.  It
has a global domain which unqualified usages reference.  Of course this
domain is selectable by the user.

@example
char *textdomain (const char *domain_name);
@end example

This provides the possibility to change or query the current status of
the current global domain of the @code{LC_MESSAGE} category.  The
argument is a null-terminated string, whose characters must be legal in
the use in filenames.  If the @var{domain_name} argument is @code{NULL},
the function return the current value.  If no value has been set
before, the name of the default domain is returned: @emph{messages}.
Please note that although the return value of @code{textdomain} is of
type @code{char *} no changing is allowed.  It is also important to know
that no checks of the availability are made.  If the name is not
available you will see this by the fact that no translations are provided.

@noindent
To use a domain set by @code{textdomain} the function

@example
char *gettext (const char *msgid);
@end example

is to be used.  This is the simplest reasonable form one can imagine.
The translation of the string @var{msgid} is returned if it is available
in the current domain.  If not available the argument itself is
returned.  If the argument is @code{NULL} the result is undefined.

One things which should come into mind is that no explicit dependency to
the used domain is given.  The current value of the domain for the
@code{LC_MESSAGES} locale is used.  If this changes between two
executions of the same @code{gettext} call in the program, both calls
reference a different message catalog.

For the easiest case, which is normally used in internationalized
packages, once at the beginning of execution a call to @code{textdomain}
is issued, setting the domain to a unique name, normally the package
name.  In the following code all strings which have to be translated are
filtered through the gettext function.  That's all, the package speaks
your language.

@node Ambiguities, Locating Catalogs, Interface to gettext, gettext
@subsection Solving Ambiguities

While this single name domain works well for most applications there
might be the need to get translations from more than one domain.  Of
course one could switch between different domains with calls to
@code{textdomain}, but this is really not convenient nor is it fast.  A
possible situation could be one case subject to discussion during this
writing:  all
error messages of functions in the set of common used functions should
go into a separate domain @code{error}.  By this mean we would only need
to translate them once.
Another case are messages from a library, as these @emph{have} to be
independent of the current domain set by the application.

@noindent
For this reasons there are two more functions to retrieve strings:

@example
char *dgettext (const char *domain_name, const char *msgid);
char *dcgettext (const char *domain_name, const char *msgid,
                 int category);
@end example

Both take an additional argument at the first place, which corresponds
to the argument of @code{textdomain}.  The third argument of
@code{dcgettext} allows to use another locale but @code{LC_MESSAGES}.
But I really don't know where this can be useful.  If the
@var{domain_name} is @code{NULL} or @var{category} has an value beside
the known ones, the result is undefined.  It should also be noted that
this function is not part of the second known implementation of this
function family, the one found in Solaris.

A second ambiguity can arise by the fact, that perhaps more than one
domain has the same name.  This can be solved by specifying where the
needed message catalog files can be found.

@example
char *bindtextdomain (const char *domain_name,
                      const char *dir_name);
@end example

Calling this function binds the given domain to a file in the specified
directory (how this file is determined follows below).  Especially a
file in the systems default place is not favored against the specified
file anymore (as it would be by solely using @code{textdomain}).  A
@code{NULL} pointer for the @var{dir_name} parameter returns the binding
associated with @var{domain_name}.  If @var{domain_name} itself is
@code{NULL} nothing happens and a @code{NULL} pointer is returned.  Here
again as for all the other functions is true that none of the return
value must be changed!

It is important to remember that relative path names for the
@var{dir_name} parameter can be trouble.  Since the path is always
computed relative to the current directory different results will be
achieved when the program executes a @code{chdir} command.  Relative
paths should always be avoided to avoid dependencies and
unreliabilities.

@node Locating Catalogs, Charset conversion, Ambiguities, gettext
@subsection Locating Message Catalog Files

Because many different languages for many different packages have to be
stored we need some way to add these information to file message catalog
files.  The way usually used in Unix environments is have this encoding
in the file name.  This is also done here.  The directory name given in
@code{bindtextdomain}s second argument (or the default directory),
followed by the value and name of the locale and the domain name are
concatenated:

@example
@var{dir_name}/@var{locale}/LC_@var{category}/@var{domain_name}.mo
@end example

The default value for @var{dir_name} is system specific.  For the GNU
library, and for packages adhering to its conventions, it's:
@example
/usr/local/share/locale
@end example

@noindent
@var{locale} is the value of the locale whose name is this
@code{LC_@var{category}}.  For @code{gettext} and @code{dgettext} this
@code{LC_@var{category}} is always @code{LC_MESSAGES}.@footnote{Some
system, eg Ultrix, don't have @code{LC_MESSAGES}.  Here we use a more or
less arbitrary value for it, namely 1729, the smallest positive integer
which can be represented in two different ways as the sum of two cubes.}
The value of the locale is determined through
@code{setlocale (LC_@var{category}, NULL)}.
@footnote{When the system does not support @code{setlocale} its behavior
in setting the locale values is simulated by looking at the environment
variables.}
@code{dcgettext} specifies the locale category by the third argument.

@node Charset conversion, Plural forms, Locating Catalogs, gettext
@subsection How to specify the output character set @code{gettext} uses

@code{gettext} not only looks up a translation in a message catalog.  It
also converts the translation on the fly to the desired output character
set.  This is useful if the user is working in a different character set
than the translator who created the message catalog, because it avoids
distributing variants of message catalogs which differ only in the
character set.

The output character set is, by default, the value of @code{nl_langinfo
(CODESET)}, which depends on the @code{LC_CTYPE} part of the current
locale.  But programs which store strings in a locale independent way
(e.g. UTF-8) can request that @code{gettext} and related functions
return the translations in that encoding, by use of the
@code{bind_textdomain_codeset} function.

Note that the @var{msgid} argument to @code{gettext} is not subject to
character set conversion.  Also, when @code{gettext} does not find a
translation for @var{msgid}, it returns @var{msgid} unchanged --
independently of the current output character set.  It is therefore
recommended that all @var{msgid}s be US-ASCII strings.

@deftypefun {char *} bind_textdomain_codeset (const char *@var{domainname}, const char *@var{codeset})
The @code{bind_textdomain_codeset} function can be used to specify the
output character set for message catalogs for domain @var{domainname}.
The @var{codeset} argument must be a valid codeset name which can be used
for the @code{iconv_open} function, or a null pointer.

If the @var{codeset} parameter is the null pointer,
@code{bind_textdomain_codeset} returns the currently selected codeset
for the domain with the name @var{domainname}. It returns @code{NULL} if
no codeset has yet been selected.

The @code{bind_textdomain_codeset} function can be used several times. 
If used multiple times with the same @var{domainname} argument, the
later call overrides the settings made by the earlier one.

The @code{bind_textdomain_codeset} function returns a pointer to a
string containing the name of the selected codeset.  The string is
allocated internally in the function and must not be changed by the
user.  If the system went out of core during the execution of
@code{bind_textdomain_codeset}, the return value is @code{NULL} and the
global variable @var{errno} is set accordingly.
@end deftypefun

@node Plural forms, GUI program problems, Charset conversion, gettext
@subsection Additional functions for plural forms

The functions of the @code{gettext} family described so far (and all the
@code{catgets} functions as well) have one problem in the real world
which have been neglected completely in all existing approaches.  What
is meant here is the handling of plural forms.

Looking through Unix source code before the time anybody thought about
internationalization (and, sadly, even afterwards) one can often find
code similar to the following:

@smallexample
   printf ("%d file%s deleted", n, n == 1 ? "" : "s");
@end smallexample

@noindent
After the first complaints from people internationalizing the code people
either completely avoided formulations like this or used strings like
@code{"file(s)"}.  Both look unnatural and should be avoided.  First
tries to solve the problem correctly looked like this:

@smallexample
   if (n == 1)
     printf ("%d file deleted", n);
   else
     printf ("%d files deleted", n);
@end smallexample

But this does not solve the problem.  It helps languages where the
plural form of a noun is not simply constructed by adding an `s' but
that is all.  Once again people fell into the trap of believing the
rules their language is using are universal.  But the handling of plural
forms differs widely between the language families.  For example,
Rafal Maszkowski @code{<rzm@@mat.uni.torun.pl>} reports:

@quotation
In Polish we use e.g. plik (file) this way:
@example
1 plik
2,3,4 pliki
5-21 pliko'w
22-24 pliki
25-31 pliko'w
@end example
and so on (o' means 8859-2 oacute which should be rather okreska,
similar to aogonek).
@end quotation

There are two things which can differ between languages (and even inside
language families);

@itemize @bullet
@item
The form how plural forms are build differs.  This is a problem with
languages which have many irregularities.  German, for instance, is a
drastic case.  Though English and German are part of the same language
family (Germanic), the almost regular forming of plural noun forms
(appending an `s') is hardly found in German.

@item
The number of plural forms differ.  This is somewhat surprising for
those who only have experiences with Romanic and Germanic languages
since here the number is the same (there are two).

But other language families have only one form or many forms.  More
information on this in an extra section.
@end itemize

The consequence of this is that application writers should not try to
solve the problem in their code.  This would be localization since it is
only usable for certain, hardcoded language environments.  Instead the
extended @code{gettext} interface should be used.

These extra functions are taking instead of the one key string two
strings and a numerical argument.  The idea behind this is that using
the numerical argument and the first string as a key, the implementation
can select using rules specified by the translator the right plural
form.  The two string arguments then will be used to provide a return
value in case no message catalog is found (similar to the normal
@code{gettext} behavior).  In this case the rules for Germanic language
is used and it is assumed that the first string argument is the singular
form, the second the plural form.

This has the consequence that programs without language catalogs can
display the correct strings only if the program itself is written using
a Germanic language.  This is a limitation but since the GNU C library
(as well as the GNU @code{gettext} package) are written as part of the
GNU package and the coding standards for the GNU project require program
being written in English, this solution nevertheless fulfills its
purpose.

@deftypefun {char *} ngettext (const char *@var{msgid1}, const char *@var{msgid2}, unsigned long int @var{n})
The @code{ngettext} function is similar to the @code{gettext} function
as it finds the message catalogs in the same way.  But it takes two
extra arguments.  The @var{msgid1} parameter must contain the singular
form of the string to be converted.  It is also used as the key for the
search in the catalog.  The @var{msgid2} parameter is the plural form.
The parameter @var{n} is used to determine the plural form.  If no
message catalog is found @var{msgid1} is returned if @code{n == 1},
otherwise @code{msgid2}.

An example for the use of this function is:

@smallexample
printf (ngettext ("%d file removed", "%d files removed", n), n);
@end smallexample

Please note that the numeric value @var{n} has to be passed to the
@code{printf} function as well.  It is not sufficient to pass it only to
@code{ngettext}.
@end deftypefun

@deftypefun {char *} dngettext (const char *@var{domain}, const char *@var{msgid1}, const char *@var{msgid2}, unsigned long int @var{n})
The @code{dngettext} is similar to the @code{dgettext} function in the
way the message catalog is selected.  The difference is that it takes
two extra parameter to provide the correct plural form.  These two
parameters are handled in the same way @code{ngettext} handles them.
@end deftypefun

@deftypefun {char *} dcngettext (const char *@var{domain}, const char *@var{msgid1}, const char *@var{msgid2}, unsigned long int @var{n}, int @var{category})
The @code{dcngettext} is similar to the @code{dcgettext} function in the
way the message catalog is selected.  The difference is that it takes
two extra parameter to provide the correct plural form.  These two
parameters are handled in the same way @code{ngettext} handles them.
@end deftypefun

Now, how do these functions solve the problem of the plural forms?
Without the input of linguists (which was not available) it was not
possible to determine whether there are only a few different forms in
which plural forms are formed or whether the number can increase with
every new supported language.

Therefore the solution implemented is to allow the translator to specify
the rules of how to select the plural form.  Since the formula varies
with every language this is the only viable solution except for
hardcoding the information in the code (which still would require the
possibility of extensions to not prevent the use of new languages).

The information about the plural form selection has to be stored in the
header entry of the PO file (the one with the empty @code{msgid} string).
The plural form information looks like this:

@smallexample
Plural-Forms: nplurals=2; plural=n == 1 ? 0 : 1;
@end smallexample

The @code{nplurals} value must be a decimal number which specifies how
many different plural forms exist for this language.  The string
following @code{plural} is an expression which is using the C language
syntax.  Exceptions are that no negative numbers are allowed, numbers
must be decimal, and the only variable allowed is @code{n}.  This
expression will be evaluated whenever one of the functions
@code{ngettext}, @code{dngettext}, or @code{dcngettext} is called.  The
numeric value passed to these functions is then substituted for all uses
of the variable @code{n} in the expression.  The resulting value then
must be greater or equal to zero and smaller than the value given as the
value of @code{nplurals}.

@noindent
The following rules are known at this point.  The language with families
are listed.  But this does not necessarily mean the information can be
generalized for the whole family (as can be easily seen in the table
below).@footnote{Additions are welcome.  Send appropriate information to
@email{bug-glibc-manual@@gnu.org}.}

@table @asis
@item Only one form:
Some languages only require one single form.  There is no distinction
between the singular and plural form.  An appropriate header entry
would look like this:

@smallexample
Plural-Forms: nplurals=1; plural=0;
@end smallexample

@noindent
Languages with this property include:

@table @asis
@item Finno-Ugric family
Hungarian
@item Asian family
Japanese, Korean
@item Turkic/Altaic family
Turkish
@end table

@item Two forms, singular used for one only
This is the form used in most existing programs since it is what English
is using.  A header entry would look like this:

@smallexample
Plural-Forms: nplurals=2; plural=n != 1;
@end smallexample

(Note: this uses the feature of C expressions that boolean expressions
have to value zero or one.)

@noindent
Languages with this property include:

@table @asis
@item Germanic family
Danish, Dutch, English, German, Norwegian, Swedish
@item Finno-Ugric family
Estonian, Finnish
@item Latin/Greek family
Greek
@item Semitic family
Hebrew
@item Romanic family
Italian, Portuguese, Spanish
@item Artificial
Esperanto
@end table

@item Two forms, singular used for zero and one
Exceptional case in the language family.  The header entry would be:

@smallexample
Plural-Forms: nplurals=2; plural=n>1;
@end smallexample

@noindent
Languages with this property include:

@table @asis
@item Romanic family
French, Brazilian Portuguese
@end table

@item Three forms, special case for zero
The header entry would be:

@smallexample
Plural-Forms: nplurals=3; plural=n%10==1 && n%100!=11 ? 0 : n != 0 ? 1 : 2;
@end smallexample

@noindent
Languages with this property include:

@table @asis
@item Baltic family
Latvian
@end table

@item Three forms, special cases for one and two
The header entry would be:

@smallexample
Plural-Forms: nplurals=3; plural=n==1 ? 0 : n==2 ? 1 : 2;
@end smallexample

@noindent
Languages with this property include:

@table @asis
@item Celtic
Gaeilge
@end table

@item Three forms, special case for numbers ending in 1[2-9]
The header entry would look like this:

@smallexample
Plural-Forms: nplurals=3; \
    plural=n%10==1 && n%100!=11 ? 0 : \
           n%10>=2 && (n%100<10 || n%100>=20) ? 1 : 2;
@end smallexample

@noindent
Languages with this property include:

@table @asis
@item Baltic family
Lithuanian
@end table

@item Three forms, special cases for numbers ending in 1 and 2, 3, 4, except those ending in 1[1-4]
The header entry would look like this:

@smallexample
Plural-Forms: nplurals=3; \
    plural=n%10==1 && n%100!=11 ? 0 : \
           n%10>=2 && n%10<=4 && (n%100<10 || n%100>=20) ? 1 : 2;
@end smallexample

@noindent
Languages with this property include:

@table @asis
@item Slavic family
Croatian, Czech, Russian, Slovak, Ukrainian
@end table

@item Three forms, special case for one and some numbers ending in 2, 3, or 4
The header entry would look like this:

@smallexample
Plural-Forms: nplurals=3; \
    plural=n==1 ? 0 : \
           n%10>=2 && n%10<=4 && (n%100<10 || n%100>=20) ? 1 : 2;
@end smallexample

@noindent
Languages with this property include:

@table @asis
@item Slavic family
Polish
@end table

@item Four forms, special case for one and all numbers ending in 02, 03, or 04
The header entry would look like this:

@smallexample
Plural-Forms: nplurals=4; \
    plural=n%100==1 ? 0 : n%100==2 ? 1 : n%100==3 || n%100==4 ? 2 : 3;
@end smallexample

@noindent
Languages with this property include:

@table @asis
@item Slavic family
Slovenian
@end table
@end table

@node GUI program problems, Optimized gettext, Plural forms, gettext
@subsection How to use @code{gettext} in GUI programs

One place where the @code{gettext} functions, if used normally, have big
problems is within programs with graphical user interfaces (GUIs).  The
problem is that many of the strings which have to be translated are very
short.  They have to appear in pull-down menus which restricts the
length.  But strings which are not containing entire sentences or at
least large fragments of a sentence may appear in more than one
situation in the program but might have different translations.  This is
especially true for the one-word strings which are frequently used in
GUI programs.

As a consequence many people say that the @code{gettext} approach is
wrong and instead @code{catgets} should be used which indeed does not
have this problem.  But there is a very simple and powerful method to
handle these kind of problems with the @code{gettext} functions.

@noindent
As as example consider the following fictional situation.  A GUI program
has a menu bar with the following entries:

@smallexample
+------------+------------+--------------------------------------+
| File       | Printer    |                                      |
+------------+------------+--------------------------------------+
| Open     | | Select   |
| New      | | Open     |
+----------+ | Connect  |
             +----------+
@end smallexample

To have the strings @code{File}, @code{Printer}, @code{Open},
@code{New}, @code{Select}, and @code{Connect} translated there has to be
at some point in the code a call to a function of the @code{gettext}
family.  But in two places the string passed into the function would be
@code{Open}.  The translations might not be the same and therefore we
are in the dilemma described above.

One solution to this problem is to artificially enlengthen the strings
to make them unambiguous.  But what would the program do if no
translation is available?  The enlengthened string is not what should be
printed.  So we should use a little bit modified version of the functions.

To enlengthen the strings a uniform method should be used.  E.g., in the
example above the strings could be chosen as

@smallexample
Menu|File
Menu|Printer
Menu|File|Open
Menu|File|New
Menu|Printer|Select
Menu|Printer|Open
Menu|Printer|Connect
@end smallexample

Now all the strings are different and if now instead of @code{gettext}
the following little wrapper function is used, everything works just
fine:

@cindex sgettext
@smallexample
  char *
  sgettext (const char *msgid)
  @{
    char *msgval = gettext (msgid);
    if (msgval == msgid)
      msgval = strrchr (msgid, '|') + 1;
    return msgval;
  @}
@end smallexample

What this little function does is to recognize the case when no
translation is available.  This can be done very efficiently by a
pointer comparison since the return value is the input value.  If there
is no translation we know that the input string is in the format we used
for the Menu entries and therefore contains a @code{|} character.  We
simply search for the last occurrence of this character and return a
pointer to the character following it.  That's it!

If one now consistently uses the enlengthened string form and replaces
the @code{gettext} calls with calls to @code{sgettext} (this is normally
limited to very few places in the GUI implementation) then it is
possible to produce a program which can be internationalized.

The other @code{gettext} functions (@code{dgettext}, @code{dcgettext}
and the @code{ngettext} equivalents) can and should have corresponding
functions as well which look almost identical, except for the parameters
and the call to the underlying function.

Now there is of course the question why such functions do not exist in
the GNU gettext package?  There are two parts of the answer to this question.

@itemize @bullet
@item
They are easy to write and therefore can be provided by the project they
are used in.  This is not an answer by itself and must be seen together
with the second part which is:

@item
There is no way the gettext package can contain a version which can work
everywhere.  The problem is the selection of the character to separate
the prefix from the actual string in the enlenghtened string.  The
examples above used @code{|} which is a quite good choice because it
resembles a notation frequently used in this context and it also is a
character not often used in message strings.

But what if the character is used in message strings?  Or if the chose
character is not available in the character set on the machine one
compiles (e.g., @code{|} is not required to exist for @w{ISO C}; this is
why the @file{iso646.h} file exists in @w{ISO C} programming environments).
@end itemize

There is only one more comment to be said.  The wrapper function above
requires that the translations strings are not enlengthened themselves.
This is only logical.  There is no need to disambiguate the strings
(since they are never used as keys for a search) and one also saves
quite some memory and disk space by doing this.

@node Optimized gettext,  , GUI program problems, gettext
@subsection Optimization of the *gettext functions

At this point of the discussion we should talk about an advantage of the
GNU @code{gettext} implementation.  Some readers might have pointed out
that an internationalized program might have a poor performance if some
string has to be translated in an inner loop.  While this is unavoidable
when the string varies from one run of the loop to the other it is
simply a waste of time when the string is always the same.  Take the
following example:

@example
@group
@{
  while (@dots{})
    @{
      puts (gettext ("Hello world"));
    @}
@}
@end group
@end example

@noindent
When the locale selection does not change between two runs the resulting
string is always the same.  One way to use this is:

@example
@group
@{
  str = gettext ("Hello world");
  while (@dots{})
    @{
      puts (str);
    @}
@}
@end group
@end example

@noindent
But this solution is not usable in all situation (e.g. when the locale
selection changes) nor does it lead to legible code.

For this reason, GNU @code{gettext} caches previous translation results.
When the same translation is requested twice, with no new message
catalogs being loaded in between, @code{gettext} will, the second time,
find the result through a single cache lookup.

@node Comparison, Using libintl.a, gettext, Programmers
@section Comparing the Two Interfaces

@c FIXME: arguments to catgets vs. gettext
@c Partly done 950718 -- drepper

The following discussion is perhaps a little bit colored.  As said
above we implemented GNU @code{gettext} following the Uniforum
proposal and this surely has its reasons.  But it should show how we
came to this decision.

First we take a look at the developing process.  When we write an
application using NLS provided by @code{gettext} we proceed as always.
Only when we come to a string which might be seen by the users and thus
has to be translated we use @code{gettext("@dots{}")} instead of
@code{"@dots{}"}.  At the beginning of each source file (or in a central
header file) we define

@example
#define gettext(String) (String)
@end example

Even this definition can be avoided when the system supports the
@code{gettext} function in its C library.  When we compile this code the
result is the same as if no NLS code is used.  When  you take a look at
the GNU @code{gettext} code you will see that we use @code{_("@dots{}")}
instead of @code{gettext("@dots{}")}.  This reduces the number of
additional characters per translatable string to @emph{3} (in words:
three).

When now a production version of the program is needed we simply replace
the definition

@example
#define _(String) (String)
@end example

@noindent
by

@example
#include <libintl.h>
#define _(String) gettext (String)
@end example

@noindent
Additionally we run the program @file{xgettext} on all source code file
which contain translatable strings and that's it: we have a running
program which does not depend on translations to be available, but which
can use any that becomes available.

The same procedure can be done for the @code{gettext_noop} invocations
(@pxref{Special cases}).  One usually defines @code{gettext_noop} as a
no-op macro.  So you should consider the following code for your project:

@example
#define gettext_noop(String) (String)
#define N_(String) gettext_noop (String)
@end example

@code{N_} is a short form similar to @code{_}.  The @file{Makefile} in
the @file{po/} directory of GNU @code{gettext} knows by default both of the
mentioned short forms so you are invited to follow this proposal for
your own ease.

Now to @code{catgets}.  The main problem is the work for the
programmer.  Every time he comes to a translatable string he has to
define a number (or a symbolic constant) which has also be defined in
the message catalog file.  He also has to take care for duplicate
entries, duplicate message IDs etc.  If he wants to have the same
quality in the message catalog as the GNU @code{gettext} program
provides he also has to put the descriptive comments for the strings and
the location in all source code files in the message catalog.  This is
nearly a Mission: Impossible.

But there are also some points people might call advantages speaking for
@code{catgets}.  If you have a single word in a string and this string
is used in different contexts it is likely that in one or the other
language the word has different translations.  Example:

@example
printf ("%s: %d", gettext ("number"), number_of_errors)

printf ("you should see %d %s", number_count,
        number_count == 1 ? gettext ("number") : gettext ("numbers"))
@end example

Here we have to translate two times the string @code{"number"}.  Even
if you do not speak a language beside English it might be possible to
recognize that the two words have a different meaning.  In German the
first appearance has to be translated to @code{"Anzahl"} and the second
to @code{"Zahl"}.

Now you can say that this example is really esoteric.  And you are
right!  This is exactly how we felt about this problem and decide that
it does not weight that much.  The solution for the above problem could
be very easy:

@example
printf ("%s %d", gettext ("number:"), number_of_errors)

printf (number_count == 1 ? gettext ("you should see %d number")
                          : gettext ("you should see %d numbers"),
        number_count)
@end example

We believe that we can solve all conflicts with this method.  If it is
difficult one can also consider changing one of the conflicting string a
little bit.  But it is not impossible to overcome.

@code{catgets} allows same original entry to have different translations,
but @code{gettext} has another, scalable approach for solving ambiguities
of this kind: @xref{Ambiguities}.

@node Using libintl.a, gettext grok, Comparison, Programmers
@section Using libintl.a in own programs

Starting with version 0.9.4 the library @code{libintl.h} should be
self-contained.  I.e., you can use it in your own programs without
providing additional functions.  The @file{Makefile} will put the header
and the library in directories selected using the @code{$(prefix)}.

One exception of the above is found on HP-UX 10.01 systems.  Here the C
library does not contain the @code{alloca} function (and the HP compiler
does not generate it inlined).  But it is not intended to rewrite the whole
library just because of this dumb system.  Instead include the
@code{alloca} function in all package you use the @code{libintl.a} in.

@node gettext grok, Temp Programmers, Using libintl.a, Programmers
@section Being a @code{gettext} grok

To fully exploit the functionality of the GNU @code{gettext} library it
is surely helpful to read the source code.  But for those who don't want
to spend that much time in reading the (sometimes complicated) code here
is a list comments:

@itemize @bullet
@item Changing the language at runtime

For interactive programs it might be useful to offer a selection of the
used language at runtime.  To understand how to do this one need to know
how the used language is determined while executing the @code{gettext}
function.  The method which is presented here only works correctly
with the GNU implementation of the @code{gettext} functions.

In the function @code{dcgettext} at every call the current setting of
the highest priority environment variable is determined and used.
Highest priority means here the following list with decreasing
priority:

@enumerate
@item @code{LANGUAGE}
@item @code{LC_ALL}
@item @code{LC_xxx}, according to selected locale
@item @code{LANG}
@end enumerate

Afterwards the path is constructed using the found value and the
translation file is loaded if available.

What is now when the value for, say, @code{LANGUAGE} changes.  According
to the process explained above the new value of this variable is found
as soon as the @code{dcgettext} function is called.  But this also means
the (perhaps) different message catalog file is loaded.  In other
words: the used language is changed.

But there is one little hook.  The code for gcc-2.7.0 and up provides
some optimization.  This optimization normally prevents the calling of
the @code{dcgettext} function as long as no new catalog is loaded.  But
if @code{dcgettext} is not called the program also cannot find the
@code{LANGUAGE} variable be changed (@pxref{Optimized gettext}).  A
solution for this is very easy.  Include the following code in the
language switching function.

@example
  /* Change language.  */
  setenv ("LANGUAGE", "fr", 1);

  /* Make change known.  */
  @{
    extern int  _nl_msg_cat_cntr;
    ++_nl_msg_cat_cntr;
  @}
@end example

The variable @code{_nl_msg_cat_cntr} is defined in @file{loadmsgcat.c}.
The programmer will find himself in need for a construct like this only
when developing programs which do run longer and provide the user to
select the language at runtime.  Non-interactive programs (like all
these little Unix tools) should never need this.

@end itemize

@node Temp Programmers,  , gettext grok, Programmers
@section Temporary Notes for the Programmers Chapter

@menu
* Temp Implementations::        Temporary - Two Possible Implementations
* Temp catgets::                Temporary - About @code{catgets}
* Temp WSI::                    Temporary - Why a single implementation
* Temp Notes::                  Temporary - Notes
@end menu

@node Temp Implementations, Temp catgets, Temp Programmers, Temp Programmers
@subsection Temporary - Two Possible Implementations

There are two competing methods for language independent messages:
the X/Open @code{catgets} method, and the Uniforum @code{gettext}
method.  The @code{catgets} method indexes messages by integers; the
@code{gettext} method indexes them by their English translations.
The @code{catgets} method has been around longer and is supported
by more vendors.  The @code{gettext} method is supported by Sun,
and it has been heard that the COSE multi-vendor initiative is
supporting it.  Neither method is a POSIX standard; the POSIX.1
committee had a lot of disagreement in this area.

Neither one is in the POSIX standard.  There was much disagreement
in the POSIX.1 committee about using the @code{gettext} routines
vs. @code{catgets} (XPG).  In the end the committee couldn't
agree on anything, so no messaging system was included as part
of the standard.  I believe the informative annex of the standard
includes the XPG3 messaging interfaces, ``@dots{}as an example of
a messaging system that has been implemented@dots{}''

They were very careful not to say anywhere that you should use one
set of interfaces over the other.  For more on this topic please
see the Programming for Internationalization FAQ.

@node Temp catgets, Temp WSI, Temp Implementations, Temp Programmers
@subsection Temporary - About @code{catgets}

There have been a few discussions of late on the use of
@code{catgets} as a base.  I think it important to present both
sides of the argument and hence am opting to play devil's advocate
for a little bit.

I'll not deny the fact that @code{catgets} could have been designed
a lot better.  It currently has quite a number of limitations and
these have already been pointed out.

However there is a great deal to be said for consistency and
standardization.  A common recurring problem when writing Unix
software is the myriad portability problems across Unix platforms.
It seems as if every Unix vendor had a look at the operating system
and found parts they could improve upon.  Undoubtedly, these
modifications are probably innovative and solve real problems.
However, software developers have a hard time keeping up with all
these changes across so many platforms.

And this has prompted the Unix vendors to begin to standardize their
systems.  Hence the impetus for Spec1170.  Every major Unix vendor
has committed to supporting this standard and every Unix software
developer waits with glee the day they can write software to this
standard and simply recompile (without having to use autoconf)
across different platforms.

As I understand it, Spec1170 is roughly based upon version 4 of the
X/Open Portability Guidelines (XPG4).  Because @code{catgets} and
friends are defined in XPG4, I'm led to believe that @code{catgets}
is a part of Spec1170 and hence will become a standardized component
of all Unix systems.

@node Temp WSI, Temp Notes, Temp catgets, Temp Programmers
@subsection Temporary - Why a single implementation

Now it seems kind of wasteful to me to have two different systems
installed for accessing message catalogs.  If we do want to remedy
@code{catgets} deficiencies why don't we try to expand @code{catgets}
(in a compatible manner) rather than implement an entirely new system.
Otherwise, we'll end up with two message catalog access systems installed
with an operating system - one set of routines for packages using GNU
@code{gettext} for their internationalization, and another set of routines
(catgets) for all other software.  Bloated?

Supposing another catalog access system is implemented.  Which do
we recommend?  At least for Linux, we need to attract as many
software developers as possible.  Hence we need to make it as easy
for them to port their software as possible.  Which means supporting
@code{catgets}.  We will be implementing the @code{libintl} code
within our @code{libc}, but does this mean we also have to incorporate
another message catalog access scheme within our @code{libc} as well?
And what about people who are going to be using the @code{libintl}
+ non-@code{catgets} routines.  When they port their software to
other platforms, they're now going to have to include the front-end
(@code{libintl}) code plus the back-end code (the non-@code{catgets}
access routines) with their software instead of just including the
@code{libintl} code with their software.

Message catalog support is however only the tip of the iceberg.
What about the data for the other locale categories.  They also have
a number of deficiencies.  Are we going to abandon them as well and
develop another duplicate set of routines (should @code{libintl}
expand beyond message catalog support)?

Like many parts of Unix that can be improved upon, we're stuck with balancing
compatibility with the past with useful improvements and innovations for
the future.

@node Temp Notes,  , Temp WSI, Temp Programmers
@subsection Temporary - Notes

X/Open agreed very late on the standard form so that many
implementations differ from the final form.  Both of my system (old
Linux catgets and Ultrix-4) have a strange variation.

OK.  After incorporating the last changes I have to spend some time on
making the GNU/Linux @code{libc} @code{gettext} functions.  So in future
Solaris is not the only system having @code{gettext}.

@node Translators, Maintainers, Programmers, Top
@chapter The Translator's View

@c FIXME: Reorganize whole chapter.

@menu
* Trans Intro 0::               Introduction 0
* Trans Intro 1::               Introduction 1
* Discussions::                 Discussions
* Organization::                Organization
* Information Flow::            Information Flow
@end menu

@node Trans Intro 0, Trans Intro 1, Translators, Translators
@section Introduction 0

Free software is going international!  The Translation Project is a way
to get maintainers, translators and users all together, so free software
will gradually become able to speak many native languages.

The GNU @code{gettext} tool set contains @emph{everything} maintainers
need for internationalizing their packages for messages.  It also
contains quite useful tools for helping translators at localizing
messages to their native language, once a package has already been
internationalized.

To achieve the Translation Project, we need many interested
people who like their own language and write it well, and who are also
able to synergize with other translators speaking the same language.
If you'd like to volunteer to @emph{work} at translating messages,
please send mail to your translating team.

Each team has its own mailing list, courtesy of Linux
International.  You may reach your translating team at the address
@file{@var{ll}@@li.org}, replacing @var{ll} by the two-letter @w{ISO 639}
code for your language.  Language codes are @emph{not} the same as
country codes given in @w{ISO 3166}.  The following translating teams
exist:

@quotation
Chinese @code{zh}, Czech @code{cs}, Danish @code{da}, Dutch @code{nl},
Esperanto @code{eo}, Finnish @code{fi}, French @code{fr}, Irish
@code{ga}, German @code{de}, Greek @code{el}, Italian @code{it},
Japanese @code{ja}, Indonesian @code{in}, Norwegian @code{no}, Polish
@code{pl}, Portuguese @code{pt}, Russian @code{ru}, Spanish @code{es},
Swedish @code{sv} and Turkish @code{tr}.
@end quotation

@noindent
For example, you may reach the Chinese translating team by writing to
@file{zh@@li.org}.  When you become a member of the translating team
for your own language, you may subscribe to its list.  For example,
Swedish people can send a message to @w{@file{sv-request@@li.org}},
having this message body:

@example
subscribe
@end example

Keep in mind that team members should be interested in @emph{working}
at translations, or at solving translational difficulties, rather than
merely lurking around.  If your team does not exist yet and you want to
start one, please write to @w{@file{translation@@iro.umontreal.ca}};
you will then reach the coordinator for all translator teams.

A handful of GNU packages have already been adapted and provided
with message translations for several languages.  Translation
teams have begun to organize, using these packages as a starting
point.  But there are many more packages and many languages for
which we have no volunteer translators.  If you would like to
volunteer to work at translating messages, please send mail to
@file{translation@@iro.umontreal.ca} indicating what language(s)
you can work on.

@node Trans Intro 1, Discussions, Trans Intro 0, Translators
@section Introduction 1

This is now official, GNU is going international!  Here is the
announcement submitted for the January 1995 GNU Bulletin:

@quotation
A handful of GNU packages have already been adapted and provided
with message translations for several languages.  Translation
teams have begun to organize, using these packages as a starting
point.  But there are many more packages and many languages
for which we have no volunteer translators.  If you'd like to
volunteer to work at translating messages, please send mail to
@samp{translation@@iro.umontreal.ca} indicating what language(s)
you can work on.
@end quotation

This document should answer many questions for those who are curious about
the process or would like to contribute.  Please at least skim over it,
hoping to cut down a little of the high volume of e-mail generated by this
collective effort towards internationalization of free software.

Most free programming which is widely shared is done in English, and
currently, English is used as the main communicating language between
national communities collaborating to free software.  This very document
is written in English.  This will not change in the foreseeable future.

However, there is a strong appetite from national communities for
having more software able to write using national language and habits,
and there is an on-going effort to modify free software in such a way
that it becomes able to do so.  The experiments driven so far raised
an enthusiastic response from pretesters, so we believe that
internationalization of free software is dedicated to succeed.

For suggestion clarifications, additions or corrections to this
document, please e-mail to @file{translation@@iro.umontreal.ca}.

@node Discussions, Organization, Trans Intro 1, Translators
@section Discussions

Facing this internationalization effort, a few users expressed their
concerns.  Some of these doubts are presented and discussed, here.

@itemize @bullet
@item Smaller groups

Some languages are not spoken by a very large number of people, so people
speaking them sometimes consider that there may not be all that much
demand such versions of free software packages.  Moreover, many people
being @emph{into computers}, in some countries, generally seem to prefer
English versions of their software.

On the other end, people might enjoy their own language a lot, and be
very motivated at providing to themselves the pleasure of having their
beloved free software speaking their mother tongue.  They do themselves
a personal favor, and do not pay that much attention to the number of
people beneficiating of their work.

@item Misinterpretation

Other users are shy to push forward their own language, seeing in this
some kind of misplaced propaganda.  Someone thought there must be some
users of the language over the networks pestering other people with it.

But any spoken language is worth localization, because there are
people behind the language for whom the language is important and
dear to their hearts.

@item Odd translations

The biggest problem is to find the right translations so that
everybody can understand the messages.  Translations are usually a
little odd.  Some people get used to English, to the extent they may
find translations into their own language ``rather pushy, obnoxious
and sometimes even hilarious.''  As a French speaking man, I have
the experience of those instruction manuals for goods, so poorly
translated in French in Korea or Taiwan@dots{}

The fact is that we sometimes have to create a kind of national
computer culture, and this is not easy without the collaboration of
many people liking their mother tongue.  This is why translations are
better achieved by people knowing and loving their own language, and
ready to work together at improving the results they obtain.

@item Dependencies over the GPL

Some people wonder if using GNU @code{gettext} necessarily brings their package
under the protective wing of the GNU General Public License, when they
do not want to make their program free, or want other kinds of freedom.
The simplest answer is yes.

The mere marking of localizable strings in a package, or conditional
inclusion of a few lines for initialization, is not really including
GPL'ed code.  However, the localization routines themselves are under
the GPL and would bring the remainder of the package under the GPL
if they were distributed with it.  So, I presume that, for those
for which this is a problem, it could be circumvented by letting to
the end installers the burden of assembling a package prepared for
localization, but not providing the localization routines themselves.

@end itemize

@node Organization, Information Flow, Discussions, Translators
@section Organization

On a larger scale, the true solution would be to organize some kind of
fairly precise set up in which volunteers could participate.  I gave
some thought to this idea lately, and realize there will be some
touchy points.  I thought of writing to Richard Stallman to launch
such a project, but feel it might be good to shake out the ideas
between ourselves first.  Most probably that Linux International has
some experience in the field already, or would like to orchestrate
the volunteer work, maybe.  Food for thought, in any case!

I guess we have to setup something early, somehow, that will help
many possible contributors of the same language to interlock and avoid
work duplication, and further be put in contact for solving together
problems particular to their tongue (in most languages, there are many
difficulties peculiar to translating technical English).  My Swedish
contributor acknowledged these difficulties, and I'm well aware of
them for French.

This is surely not a technical issue, but we should manage so the
effort of locale contributors be maximally useful, despite the national
team layer interface between contributors and maintainers.

The Translation Project needs some setup for coordinating language
coordinators.  Localizing evolving programs will surely
become a permanent and continuous activity in the free software community,
once well started.
The setup should be minimally completed and tested before GNU
@code{gettext} becomes an official reality.  The e-mail address
@file{translation@@iro.umontreal.ca} has been setup for receiving
offers from volunteers and general e-mail on these topics.  This address
reaches the Translation Project coordinator.

@menu
* Central Coordination::        Central Coordination
* National Teams::              National Teams
* Mailing Lists::               Mailing Lists
@end menu

@node Central Coordination, National Teams, Organization, Organization
@subsection Central Coordination

I also think GNU will need sooner than it thinks, that someone setup
a way to organize and coordinate these groups.  Some kind of group
of groups.  My opinion is that it would be good that GNU delegates
this task to a small group of collaborating volunteers, shortly.
Perhaps in @file{gnu.announce} a list of this national committee's
can be published.

My role as coordinator would simply be to refer to Ulrich any German
speaking volunteer interested to localization of free software packages, and
maybe helping national groups to initially organize, while maintaining
national registries for until national groups are ready to take over.
In fact, the coordinator should ease volunteers to get in contact with
one another for creating national teams, which should then select
one coordinator per language, or country (regionalized language).
If well done, the coordination should be useful without being an
overwhelming task, the time to put delegations in place.

@node National Teams, Mailing Lists, Central Coordination, Organization
@subsection National Teams

I suggest we look for volunteer coordinators/editors for individual
languages.  These people will scan contributions of translation files
for various programs, for their own languages, and will ensure high
and uniform standards of diction.

From my current experience with other people in these days, those who
provide localizations are very enthusiastic about the process, and are
more interested in the localization process than in the program they
localize, and want to do many programs, not just one.  This seems
to confirm that having a coordinator/editor for each language is a
good idea.

We need to choose someone who is good at writing clear and concise
prose in the language in question.  That is hard---we can't check
it ourselves.  So we need to ask a few people to judge each others'
writing and select the one who is best.

I announce my prerelease to a few dozen people, and you would not
believe all the discussions it generated already.  I shudder to think
what will happen when this will be launched, for true, officially,
world wide.  Who am I to arbitrate between two Czekolsovak users
contradicting each other, for example?

I assume that your German is not much better than my French so that
I would not be able to judge about these formulations.  What I would
suggest is that for each language there is a group for people who
maintain the PO files and judge about changes.  I suspect there will
be cultural differences between how such groups of people will behave.
Some will have relaxed ways, reach consensus easily, and have anyone
of the group relate to the maintainers, while others will fight to
death, organize heavy administrations up to national standards, and
use strict channels.

The German team is putting out a good example.  Right now, they are
maybe half a dozen people revising translations of each other and
discussing the linguistic issues.  I do not even have all the names.
Ulrich Drepper is taking care of coordinating the German team.
He subscribed to all my pretest lists, so I do not even have to warn
him specifically of incoming releases.

I'm sure, that is a good idea to get teams for each language working
on translations. That will make the translations better and more
consistent.

@menu
* Sub-Cultures::                Sub-Cultures
* Organizational Ideas::        Organizational Ideas
@end menu

@node Sub-Cultures, Organizational Ideas, National Teams, National Teams
@subsubsection Sub-Cultures

Taking French for example, there are a few sub-cultures around computers
which developed diverging vocabularies.  Picking volunteers here and
there without addressing this problem in an organized way, soon in the
project, might produce a distasteful mix of internationalized programs,
and possibly trigger endless quarrels among those who really care.

Keeping some kind of unity in the way French localization of
internationalized programs is achieved is a difficult (and delicate) job.
Knowing the latin character of French people (:-), if we take this
the wrong way, we could end up nowhere, or spoil a lot of energies.
Maybe we should begin to address this problem seriously @emph{before}
GNU @code{gettext} become officially published.  And I suspect that this
means soon!

@node Organizational Ideas,  , Sub-Cultures, National Teams
@subsubsection Organizational Ideas

I expect the next big changes after the official release.  Please note
that I use the German translation of the short GPL message.  We need
to set a few good examples before the localization goes out for true
in the free software community.  Here are a few points to discuss:

@itemize @bullet
@item
Each group should have one FTP server (at least one master).

@item
The files on the server should reflect the latest version (of
course!) and it should also contain a RCS directory with the
corresponding archives (I don't have this now).

@item
There should also be a ChangeLog file (this is more useful than the
RCS archive but can be generated automatically from the later by
Emacs).

@item
A @dfn{core group} should judge about questionable changes (for now
this group consists solely by me but I ask some others occasionally;
this also seems to work).

@end itemize

@node Mailing Lists,  , National Teams, Organization
@subsection Mailing Lists

If we get any inquiries about GNU @code{gettext}, send them on to:

@example
@file{translation@@iro.umontreal.ca}
@end example

The @file{*-pretest} lists are quite useful to me, maybe the idea could
be generalized to many GNU, and non-GNU packages.  But each maintainer
his/her way!

Fran@,{c}ois, we have a mechanism in place here at
@file{gnu.ai.mit.edu} to track teams, support mailing lists for
them and log members.  We have a slight preference that you use it.
If this is OK with you, I can get you clued in.

Things are changing!  A few years ago, when Daniel Fekete and I
asked for a mailing list for GNU localization, nested at the FSF, we
were politely invited to organize it anywhere else, and so did we.
For communicating with my pretesters, I later made a handful of
mailing lists located at iro.umontreal.ca and administrated by
@code{majordomo}.  These lists have been @emph{very} dependable
so far@dots{}

I suspect that the German team will organize itself a mailing list
located in Germany, and so forth for other countries.  But before they
organize for true, it could surely be useful to offer mailing lists
located at the FSF to each national team.  So yes, please explain me
how I should proceed to create and handle them.

We should create temporary mailing lists, one per country, to help
people organize.  Temporary, because once regrouped and structured, it
would be fair the volunteers from country bring back @emph{their} list
in there and manage it as they want.  My feeling is that, in the long
run, each team should run its own list, from within their country.
There also should be some central list to which all teams could
subscribe as they see fit, as long as each team is represented in it.

@node Information Flow,  , Organization, Translators
@section Information Flow

There will surely be some discussion about this messages after the
packages are finally released.  If people now send you some proposals
for better messages, how do you proceed?  Jim, please note that
right now, as I put forward nearly a dozen of localizable programs, I
receive both the translations and the coordination concerns about them.

If I put one of my things to pretest, Ulrich receives the announcement
and passes it on to the German team, who make last minute revisions.
Then he submits the translation files to me @emph{as the maintainer}.
For free packages I do not maintain, I would not even hear about it.
This scheme could be made to work for the whole Translation Project,
I think.  For security reasons, maybe Ulrich (national coordinators,
in fact) should update central registry kept at the Translation Project
(Jim, me, or Len's recruits) once in a while.

In December/January, I was aggressively ready to internationalize
all of GNU, giving myself the duty of one small GNU package per week
or so, taking many weeks or months for bigger packages.  But it does
not work this way.  I first did all the things I'm responsible for.
I've nothing against some missionary work on other maintainers, but
I'm also loosing a lot of energy over it---same debates over again.

And when the first localized packages are released we'll get a lot of
responses about ugly translations :-).  Surely, and we need to have
beforehand a fairly good idea about how to handle the information
flow between the national teams and the package maintainers.

Please start saving somewhere a quick history of each PO file.  I know
for sure that the file format will change, allowing for comments.
It would be nice that each file has a kind of log, and references for
those who want to submit comments or gripes, or otherwise contribute.
I sent a proposal for a fast and flexible format, but it is not
receiving acceptance yet by the GNU deciders.  I'll tell you when I
have more information about this.

@node Maintainers, Conclusion, Translators, Top
@chapter The Maintainer's View

The maintainer of a package has many responsibilities.  One of them
is ensuring that the package will install easily on many platforms,
and that the magic we described earlier (@pxref{Users}) will work
for installers and end users.

Of course, there are many possible ways by which GNU @code{gettext}
might be integrated in a distribution, and this chapter does not cover
them in all generality.  Instead, it details one possible approach which
is especially adequate for many free software distributions following GNU
standards, or even better, Gnits standards, because GNU @code{gettext}
is purposely for helping the internationalization of the whole GNU
project, and as many other good free packages as possible.  So, the
maintainer's view presented here presumes that the package already has
a @file{configure.in} file and uses GNU Autoconf.

Nevertheless, GNU @code{gettext} may surely be useful for free packages
not following GNU standards and conventions, but the maintainers of such
packages might have to show imagination and initiative in organizing
their distributions so @code{gettext} work for them in all situations.
There are surely many, out there.

Even if @code{gettext} methods are now stabilizing, slight adjustments
might be needed between successive @code{gettext} versions, so you
should ideally revise this chapter in subsequent releases, looking
for changes.

@menu
* Flat and Non-Flat::           Flat or Non-Flat Directory Structures
* Prerequisites::               Prerequisite Works
* gettextize Invocation::       Invoking the @code{gettextize} Program
* Adjusting Files::             Files You Must Create or Alter
@end menu

@node Flat and Non-Flat, Prerequisites, Maintainers, Maintainers
@section Flat or Non-Flat Directory Structures

Some free software packages are distributed as @code{tar} files which unpack
in a single directory, these are said to be @dfn{flat} distributions.
Other free software packages have a one level hierarchy of subdirectories, using
for example a subdirectory named @file{doc/} for the Texinfo manual and
man pages, another called @file{lib/} for holding functions meant to
replace or complement C libraries, and a subdirectory @file{src/} for
holding the proper sources for the package.  These other distributions
are said to be @dfn{non-flat}.

We cannot say much about flat distributions.  A flat
directory structure has the disadvantage of increasing the difficulty
of updating to a new version of GNU @code{gettext}.  Also, if you have
many PO files, this could somewhat pollute your single directory.
Also, GNU @code{gettext}'s libintl sources consist of C sources, shell
scripts, @code{sed} scripts and complicated Makefile rules, which don't
fit well into an existing flat structure.  For these reasons, we
recommend to use non-flat approach in this case as well.

Maybe because GNU @code{gettext} itself has a non-flat structure,
we have more experience with this approach, and this is what will be
described in the remaining of this chapter.  Some maintainers might
use this as an opportunity to unflatten their package structure.

@node Prerequisites, gettextize Invocation, Flat and Non-Flat, Maintainers
@section Prerequisite Works

There are some works which are required for using GNU @code{gettext}
in one of your package.  These works have some kind of generality
that escape the point by point descriptions used in the remainder
of this chapter.  So, we describe them here.

@itemize @bullet
@item
Before attempting to use @code{gettextize} you should install some
other packages first.
Ensure that recent versions of GNU @code{m4}, GNU Autoconf and GNU
@code{gettext} are already installed at your site, and if not, proceed
to do this first.  If you got to install these things, beware that
GNU @code{m4} must be fully installed before GNU Autoconf is even
@emph{configured}.

To further ease the task of a package maintainer the @code{automake}
package was designed and implemented.  GNU @code{gettext} now uses this
tool and the @file{Makefile}s in the @file{intl/} and @file{po/}
therefore know about all the goals necessary for using @code{automake}
and @file{libintl} in one project.

Those four packages are only needed to you, as a maintainer; the
installers of your own package and end users do not really need any of
GNU @code{m4}, GNU Autoconf, GNU @code{gettext}, or GNU @code{automake}
for successfully installing and running your package, with messages
properly translated.  But this is not completely true if you provide
internationalized shell scripts within your own package: GNU
@code{gettext} shall then be installed at the user site if the end users
want to see the translation of shell script messages.

@item
Your package should use Autoconf and have a @file{configure.in} file.
If it does not, you have to learn how.  The Autoconf documentation
is quite well written, it is a good idea that you print it and get
familiar with it.

@item
Your C sources should have already been modified according to
instructions given earlier in this manual.  @xref{Sources}.

@item
Your @file{po/} directory should receive all PO files submitted to you
by the translator teams, each having @file{@var{ll}.po} as a name.
This is not usually easy to get translation
work done before your package gets internationalized and available!
Since the cycle has to start somewhere, the easiest for the maintainer
is to start with absolutely no PO files, and wait until various
translator teams get interested in your package, and submit PO files.

@end itemize

It is worth adding here a few words about how the maintainer should
ideally behave with PO files submissions.  As a maintainer, your role is
to authentify the origin of the submission as being the representative
of the appropriate translating teams of the Translation Project (forward
the submission to @file{translation@@iro.umontreal.ca} in case of doubt),
to ensure that the PO file format is not severely broken and does not
prevent successful installation, and for the rest, to merely to put these
PO files in @file{po/} for distribution.

As a maintainer, you do not have to take on your shoulders the
responsibility of checking if the translations are adequate or
complete, and should avoid diving into linguistic matters.  Translation
teams drive themselves and are fully responsible of their linguistic
choices for the Translation Project.  Keep in mind that translator teams are @emph{not}
driven by maintainers.  You can help by carefully redirecting all
communications and reports from users about linguistic matters to the
appropriate translation team, or explain users how to reach or join
their team.  The simplest might be to send them the @file{ABOUT-NLS} file.

Maintainers should @emph{never ever} apply PO file bug reports
themselves, short-cutting translation teams.  If some translator has
difficulty to get some of her points through her team, it should not be
an issue for her to directly negotiate translations with maintainers.
Teams ought to settle their problems themselves, if any.  If you, as
a maintainer, ever think there is a real problem with a team, please
never try to @emph{solve} a team's problem on your own.

@node gettextize Invocation, Adjusting Files, Prerequisites, Maintainers
@section Invoking the @code{gettextize} Program

Some files are consistently and identically needed in every package
internationalized through GNU @code{gettext}.  As a matter of
convenience, the @code{gettextize} program puts all these files right
in your package.  This program has the following synopsis:

@example
gettextize [ @var{option}@dots{} ] [ @var{directory} ]
@end example

@noindent
and accepts the following options:

@table @samp
@item -c
@itemx --copy
Copy the needed files instead of making symbolic links.  Using links
would allow the package to always use the latest @code{gettext} code
available on the system, but it might disturb some mechanism the
maintainer is used to apply to the sources.  Because running
@code{gettextize} is easy there shouldn't be problems with using copies.

@item -f
@itemx --force
Force replacement of files which already exist.

@item -h
@itemx --help
Display this help and exit.

@item --version
Output version information and exit.

@end table

If @var{directory} is given, this is the top level directory of a
package to prepare for using GNU @code{gettext}.  If not given, it
is assumed that the current directory is the top level directory of
such a package.

The program @code{gettextize} provides the following files.  However,
no existing file will be replaced unless the option @code{--force}
(@code{-f}) is specified.

@enumerate
@item
The @file{ABOUT-NLS} file is copied in the main directory of your package,
the one being at the top level.  This file gives the main indications
about how to install and use the Native Language Support features
of your program.  You might elect to use a more recent copy of this
@file{ABOUT-NLS} file than the one provided through @code{gettextize},
if you have one handy.  You may also fetch a more recent copy of file
@file{ABOUT-NLS} from Translation Project sites, and from most GNU
archive sites.

@item
A @file{po/} directory is created for eventually holding
all translation files, but initially only containing the file
@file{po/Makefile.in.in} from the GNU @code{gettext} distribution.
(beware the double @samp{.in} in the file name). If the @file{po/}
directory already exists, it will be preserved along with the files
it contains, and only @file{Makefile.in.in} will be overwritten.

@item
A @file{intl/} directory is created and filled with most of the files
originally in the @file{intl/} directory of the GNU @code{gettext}
distribution.  Also, if option @code{--force} (@code{-f}) is given,
the @file{intl/} directory is emptied first.

@end enumerate

If your site support symbolic links, @code{gettextize} will not
actually copy the files into your package, but establish symbolic
links instead.  This avoids duplicating the disk space needed in
all packages.  Merely using the @samp{-h} option while creating the
@code{tar} archive of your distribution will resolve each link by an
actual copy in the distribution archive.  So, to insist, you really
should use @samp{-h} option with @code{tar} within your @code{dist}
goal of your main @file{Makefile.in}.

It is interesting to understand that most new files for supporting
GNU @code{gettext} facilities in one package go in @file{intl/}
and @file{po/} subdirectories.  One distinction between these two
directories is that @file{intl/} is meant to be completely identical
in all packages using GNU @code{gettext}, while all newly created
files, which have to be different, go into @file{po/}.  There is a
common @file{Makefile.in.in} in @file{po/}, because the @file{po/}
directory needs its own @file{Makefile}, and it has been designed so
it can be identical in all packages.

@node Adjusting Files,  , gettextize Invocation, Maintainers
@section Files You Must Create or Alter

Besides files which are automatically added through @code{gettextize},
there are many files needing revision for properly interacting with
GNU @code{gettext}.  If you are closely following GNU standards for
Makefile engineering and auto-configuration, the adaptations should
be easier to achieve.  Here is a point by point description of the
changes needed in each.

So, here comes a list of files, each one followed by a description of
all alterations it needs.  Many examples are taken out from the GNU
@code{gettext} @value{VERSION} distribution itself.  You may indeed
refer to the source code of the GNU @code{gettext} package, as it
is intended to be a good example and master implementation for using
its own functionality.

@menu
* po/POTFILES.in::              @file{POTFILES.in} in @file{po/}
* configure.in::                @file{configure.in} at top level
* config.guess::                @file{config.guess}, @file{config.sub} at top level
* aclocal::                     @file{aclocal.m4} at top level
* acconfig::                    @file{acconfig.h} at top level
* Makefile::                    @file{Makefile.in} at top level
* src/Makefile::                @file{Makefile.in} in @file{src/}
@end menu

@node po/POTFILES.in, configure.in, Adjusting Files, Adjusting Files
@subsection @file{POTFILES.in} in @file{po/}

The @file{po/} directory should receive a file named
@file{POTFILES.in}.  This file tells which files, among all program
sources, have marked strings needing translation.  Here is an example
of such a file:

@example
@group
# List of source files containing translatable strings.
# Copyright (C) 1995 Free Software Foundation, Inc.

# Common library files
lib/error.c
lib/getopt.c
lib/xmalloc.c

# Package source files
src/gettext.c
src/msgfmt.c
src/xgettext.c
@end group
@end example

@noindent
Hash-marked comments and white lines are ignored.  All other lines
list those source files containing strings marked for translation
(@pxref{Mark Keywords}), in a notation relative to the top level
of your whole distribution, rather than the location of the
@file{POTFILES.in} file itself.

@node configure.in, config.guess, po/POTFILES.in, Adjusting Files
@subsection @file{configure.in} at top level

@enumerate
@item Declare the package and version.

This is done by a set of lines like these:

@example
PACKAGE=gettext
VERSION=@value{VERSION}
AC_DEFINE_UNQUOTED(PACKAGE, "$PACKAGE")
AC_DEFINE_UNQUOTED(VERSION, "$VERSION")
AC_SUBST(PACKAGE)
AC_SUBST(VERSION)
@end example

@noindent
Of course, you replace @samp{gettext} with the name of your package,
and @samp{@value{VERSION}} by its version numbers, exactly as they
should appear in the packaged @code{tar} file name of your distribution
(@file{gettext-@value{VERSION}.tar.gz}, here).

@item Declare the available translations.

This is done by defining @code{ALL_LINGUAS} to the white separated,
quoted list of available languages, in a single line, like this:

@example
ALL_LINGUAS="de fr"
@end example

@noindent
This example means that German and French PO files are available, so
that these languages are currently supported by your package.  If you
want to further restrict, at installation time, the set of installed
languages, this should not be done by modifying @code{ALL_LINGUAS} in
@file{configure.in}, but rather by using the @code{LINGUAS} environment
variable (@pxref{Installers}).

@item Check for internationalization support.

Here is the main @code{m4} macro for triggering internationalization
support.  Just add this line to @file{configure.in}:

@example
AM_GNU_GETTEXT
@end example

@noindent
This call is purposely simple, even if it generates a lot of configure
time checking and actions.

@item Have output files created.

The @code{AC_OUTPUT} directive, at the end of your @file{configure.in}
file, needs to be modified in two ways:

@example
AC_OUTPUT([@var{existing configuration files} intl/Makefile po/Makefile.in],
@var{existing additional actions}])
@end example

The modification to the first argument to @code{AC_OUTPUT} asks
for substitution in the @file{intl/} and @file{po/} directories.
Note the @samp{.in} suffix used for @file{po/} only.  This is because
the distributed file is really @file{po/Makefile.in.in}.

@end enumerate

@node config.guess, aclocal, configure.in, Adjusting Files
@subsection @file{config.guess}, @file{config.sub} at top level

You need to add the GNU @file{config.guess} and @file{config.sub} files
to your distribution.  They are needed because the @file{intl/} directory
has platform dependent support for determining the locale's character
encoding and therefore needs to identify the platform.

You can obtain the newest version of @file{config.guess} and
@file{config.sub} from @file{ftp://ftp.gnu.org/pub/gnu/config/}.
Less recent versions are also contained in the GNU @code{automake} and
GNU @code{libtool} packages.

Normally, @file{config.guess} and @file{config.sub} are put at the
top level of a distribution.  But it is also possible to put them in a
subdirectory, altogether with other configuration support files like
@file{install-sh}, @file{ltconfig}, @file{ltmain.sh},
@file{mkinstalldirs} or @file{missing}.  All you need to do, other than
moving the files, is to add the following line to your
@file{configure.in}.

@example
AC_CONFIG_AUX_DIR([@var{subdir}])
@end example

@node aclocal, acconfig, config.guess, Adjusting Files
@subsection @file{aclocal.m4} at top level

If you do not have an @file{aclocal.m4} file in your distribution,
the simplest is to concatenate the files @file{codeset.m4},
@file{gettext.m4}, @file{glibc21.m4}, @file{iconv.m4}, @file{isc-posix.m4},
@file{lcmessage.m4}, @file{progtest.m4} from GNU @code{gettext}'s
@file{m4/} directory into a single file.

If you already have an @file{aclocal.m4} file, then you will have
to merge the said macro files into your @file{aclocal.m4}.  Note that if
you are upgrading from a previous release of GNU @code{gettext}, you
should most probably @emph{replace} the macros (@code{AM_GNU_GETTEXT},
@code{AM_WITH_NLS}, etc.), as they usually
change a little from one release of GNU @code{gettext} to the next.
Their contents may vary as we get more experience with strange systems
out there.

These macros check for the internationalization support functions
and related informations.  Hopefully, once stabilized, these macros
might be integrated in the standard Autoconf set, because this
piece of @code{m4} code will be the same for all projects using GNU
@code{gettext}.

@node acconfig, Makefile, aclocal, Adjusting Files
@subsection @file{acconfig.h} at top level

Earlier GNU @code{gettext} releases required to put definitions for
@code{ENABLE_NLS}, @code{HAVE_GETTEXT} and @code{HAVE_LC_MESSAGES},
@code{HAVE_STPCPY}, @code{PACKAGE} and @code{VERSION} into an
@file{acconfig.h} file.  This is not needed any more; you can remove
them from your @file{acconfig.h} file unless your package uses them
independently from the @file{intl/} directory.

@node Makefile, src/Makefile, acconfig, Adjusting Files
@subsection @file{Makefile.in} at top level

Here are a few modifications you need to make to your main, top-level
@file{Makefile.in} file.

@enumerate
@item
Add the following lines near the beginning of your @file{Makefile.in},
so the @samp{dist:} goal will work properly (as explained further down):

@example
PACKAGE = @@PACKAGE@@
VERSION = @@VERSION@@
@end example

@item
Add file @file{ABOUT-NLS} to the @code{DISTFILES} definition, so the file gets
distributed.

@item
Wherever you process subdirectories in your @file{Makefile.in}, be sure
you also process dir subdirectories @samp{intl} and @samp{po}.  Special
rules in the @file{Makefiles} take care for the case where no
internationalization is wanted.

If you are using Makefiles, either generated by automake, or hand-written
so they carefully follow the GNU coding standards, the effected goals for
which the new subdirectories must be handled include @samp{installdirs},
@samp{install}, @samp{uninstall}, @samp{clean}, @samp{distclean}.

Here is an example of a canonical order of processing.  In this
example, we also define @code{SUBDIRS} in @code{Makefile.in} for it
to be further used in the @samp{dist:} goal.

@example
SUBDIRS = doc intl lib src @@POSUB@@
@end example

Note that you must arrange for @samp{make} to descend into the
@code{intl} directory before descending into other directories containing
code which make use of the @code{libintl.h} header file.  For this
reason, here we mention @code{intl} before @code{lib} and @code{src}.

@noindent
that you will have to adapt to your own package.

@item
A delicate point is the @samp{dist:} goal, as both
@file{intl/Makefile} and @file{po/Makefile} will later assume that the
proper directory has been set up from the main @file{Makefile}.  Here is
an example at what the @samp{dist:} goal might look like:

@example
distdir = $(PACKAGE)-$(VERSION)
dist: Makefile
	rm -fr $(distdir)
	mkdir $(distdir)
	chmod 777 $(distdir)
	for file in $(DISTFILES); do \
	  ln $$file $(distdir) 2>/dev/null || cp -p $$file $(distdir); \
	done
	for subdir in $(SUBDIRS); do \
	  mkdir $(distdir)/$$subdir || exit 1; \
	  chmod 777 $(distdir)/$$subdir; \
	  (cd $$subdir && $(MAKE) $@@) || exit 1; \
	done
	tar chozf $(distdir).tar.gz $(distdir)
	rm -fr $(distdir)
@end example

@end enumerate

@node src/Makefile,  , Makefile, Adjusting Files
@subsection @file{Makefile.in} in @file{src/}

Some of the modifications made in the main @file{Makefile.in} will
also be needed in the @file{Makefile.in} from your package sources,
which we assume here to be in the @file{src/} subdirectory.  Here are
all the modifications needed in @file{src/Makefile.in}:

@enumerate
@item
In view of the @samp{dist:} goal, you should have these lines near the
beginning of @file{src/Makefile.in}:

@example
PACKAGE = @@PACKAGE@@
VERSION = @@VERSION@@
@end example

@item
If not done already, you should guarantee that @code{top_srcdir}
gets defined.  This will serve for @code{cpp} include files.  Just add
the line:

@example
top_srcdir = @@top_srcdir@@
@end example

@item
You might also want to define @code{subdir} as @samp{src}, later
allowing for almost uniform @samp{dist:} goals in all your
@file{Makefile.in}.  At list, the @samp{dist:} goal below assume that
you used:

@example
subdir = src
@end example

@item
The @code{main} function of your program will normally call
@code{bindtextdomain} (see @pxref{Triggering}), like this:

@example
bindtextdomain (@var{PACKAGE}, LOCALEDIR);
@end example

To make LOCALEDIR known to the program, add the following lines to
Makefile.in:

@example
datadir = @@datadir@@
localedir = $(datadir)/locale
DEFS = -DLOCALEDIR=\"$(localedir)\" @@DEFS@@
@end example

Note that @code{@@datadir@@} defaults to @samp{$(prefix)/share}, thus
@code{$(localedir)} defaults to @samp{$(prefix)/share/locale}.

@item
You should ensure that the final linking will use @code{@@INTLLIBS@@} as
a library.  An easy way to achieve this is to manage that it gets into
@code{LIBS}, like this:

@example
LIBS = @@INTLLIBS@@ @@LIBS@@
@end example

In most packages internationalized with GNU @code{gettext}, one will
find a directory @file{lib/} in which a library containing some helper
functions will be build.  (You need at least the few functions which the
GNU @code{gettext} Library itself needs.)  However some of the functions
in the @file{lib/} also give messages to the user which of course should be
translated, too.  Taking care of this it is not enough to place the support
library (say @file{libsupport.a}) just between the @code{@@INTLLIBS@@}
and @code{@@LIBS@@} in the above example.  Instead one has to write this:

@example
LIBS = ../lib/libsupport.a @@INTLLIBS@@ ../lib/libsupport.a @@LIBS@@
@end example

@item
You should also ensure that directory @file{intl/} will be searched for
C preprocessor include files in all circumstances.  So, you have to
manage so both @samp{-I../intl} and @samp{-I$(top_srcdir)/intl} will
be given to the C compiler.

@item
Your @samp{dist:} goal has to conform with others.  Here is a
reasonable definition for it:

@example
distdir = ../$(PACKAGE)-$(VERSION)/$(subdir)
dist: Makefile $(DISTFILES)
	for file in $(DISTFILES); do \
	  ln $$file $(distdir) 2>/dev/null || cp -p $$file $(distdir); \
	done
@end example

@end enumerate

@node Conclusion, Language Codes, Maintainers, Top
@chapter Concluding Remarks

We would like to conclude this GNU @code{gettext} manual by presenting
an history of the Translation Project so far.  We finally give
a few pointers for those who want to do further research or readings
about Native Language Support matters.

@menu
* History::                     History of GNU @code{gettext}
* References::                  Related Readings
@end menu

@node History, References, Conclusion, Conclusion
@section History of GNU @code{gettext}

Internationalization concerns and algorithms have been informally
and casually discussed for years in GNU, sometimes around GNU
@code{libc}, maybe around the incoming @code{Hurd}, or otherwise
(nobody clearly remembers).  And even then, when the work started for
real, this was somewhat independently of these previous discussions.

This all began in July 1994, when Patrick D'Cruze had the idea and
initiative of internationalizing version 3.9.2 of GNU @code{fileutils}.
He then asked Jim Meyering, the maintainer, how to get those changes
folded into an official release.  That first draft was full of
@code{#ifdef}s and somewhat disconcerting, and Jim wanted to find
nicer ways.  Patrick and Jim shared some tries and experimentations
in this area.  Then, feeling that this might eventually have a deeper
impact on GNU, Jim wanted to know what standards were, and contacted
Richard Stallman, who very quickly and verbally described an overall
design for what was meant to become @code{glocale}, at that time.

Jim implemented @code{glocale} and got a lot of exhausting feedback
from Patrick and Richard, of course, but also from Mitchum DSouza
(who wrote a @code{catgets}-like package), Roland McGrath, maybe David
MacKenzie, Fran@,{c}ois Pinard, and Paul Eggert, all pushing and
pulling in various directions, not always compatible, to the extent
that after a couple of test releases, @code{glocale} was torn apart.

While Jim took some distance and time and became dad for a second
time, Roland wanted to get GNU @code{libc} internationalized, and
got Ulrich Drepper involved in that project.  Instead of starting
from @code{glocale}, Ulrich rewrote something from scratch, but
more conformant to the set of guidelines who emerged out of the
@code{glocale} effort.  Then, Ulrich got people from the previous
forum to involve themselves into this new project, and the switch
from @code{glocale} to what was first named @code{msgutils}, renamed
@code{nlsutils}, and later @code{gettext}, became officially accepted
by Richard in May 1995 or so.

Let's summarize by saying that Ulrich Drepper wrote GNU @code{gettext}
in April 1995.  The first official release of the package, including
PO mode, occurred in July 1995, and was numbered 0.7.  Other people
contributed to the effort by providing a discussion forum around
Ulrich, writing little pieces of code, or testing.  These are quoted
in the @code{THANKS} file which comes with the GNU @code{gettext}
distribution.

While this was being done, Fran@,{c}ois adapted half a dozen of
GNU packages to @code{glocale} first, then later to @code{gettext},
putting them in pretest, so providing along the way an effective
user environment for fine tuning the evolving tools.  He also took
the responsibility of organizing and coordinating the Translation
Project.  After nearly a year of informal exchanges between people from
many countries, translator teams started to exist in May 1995, through
the creation and support by Patrick D'Cruze of twenty unmoderated
mailing lists for that many native languages, and two moderated
lists: one for reaching all teams at once, the other for reaching
all willing maintainers of internationalized free software packages.

Fran@,{c}ois also wrote PO mode in June 1995 with the collaboration
of Greg McGary, as a kind of contribution to Ulrich's package.
He also gave a hand with the GNU @code{gettext} Texinfo manual.

@node References,  , History, Conclusion
@section Related Readings

Eugene H. Dorr (@file{dorre@@well.com}) maintains an interesting
bibliography on internationalization matters, called
@cite{Internationalization Reference List}, which is available as:
@example
ftp://ftp.ora.com/pub/examples/nutshell/ujip/doc/i18n-books.txt
@end example

Michael Gschwind (@file{mike@@vlsivie.tuwien.ac.at}) maintains a
Frequently Asked Questions (FAQ) list, entitled @cite{Programming for
Internationalisation}.  This FAQ discusses writing programs which
can handle different language conventions, character sets, etc.;
and is applicable to all character set encodings, with particular
emphasis on @w{ISO 8859-1}.  It is regularly published in Usenet
groups @file{comp.unix.questions}, @file{comp.std.internat},
@file{comp.software.international}, @file{comp.lang.c},
@file{comp.windows.x}, @file{comp.std.c}, @file{comp.answers}
and @file{news.answers}.  The home location of this document is:
@example
ftp://ftp.vlsivie.tuwien.ac.at/pub/8bit/ISO-programming
@end example

Patrick D'Cruze (@file{pdcruze@@li.org}) wrote a tutorial about NLS
matters, and Jochen Hein (@file{Hein@@student.tu-clausthal.de}) took
over the responsibility of maintaining it.  It may be found as:
@example
ftp://sunsite.unc.edu/pub/Linux/utils/nls/catalogs/Incoming/...
     ...locale-tutorial-0.8.txt.gz
@end example
@noindent
This site is mirrored in:
@example
ftp://ftp.ibp.fr/pub/linux/sunsite/
@end example

A French version of the same tutorial should be findable at:
@example
ftp://ftp.ibp.fr/pub/linux/french/docs/
@end example
@noindent
together with French translations of many Linux-related documents.

@node Language Codes, Country Codes, Conclusion, Top
@appendix Language Codes

The @w{ISO 639} standard defines two character codes for many languages.
All abbreviations for languages used in the Translation Project should
come from this standard.

@table @samp
@include iso-639.texi
@end table

@node Country Codes,  , Language Codes, Top
@appendix Country Codes

The @w{ISO 3166} standard defines two character codes for many countries
and territories.  All abbreviations for countries used in the Translation
Project should come from this standard.

@table @samp
@include iso-3166.texi
@end table

@contents
@bye

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