gettext

Initially, POSIX provided no means of localizing messages. Two proposals were raised in the late 1980s, the 1988 Uniforum gettext and the 1989 X/Open catgets (XPG-3 § 5). Sun Microsystems implemented the first gettext in 1993. The Unix and POSIX developers never really agreed on what kind of interface to use (the other option is the X/Open catgets), so many C libraries, including glibc, implemented both.{{cite web |title=Message Translation |url=https://www.gnu.org/software/libc/manual/html_node/Message-Translation.html |website=The GNU C Library}} {{As of|2019|08}}, whether gettext should be part of POSIX was still a point of debate in the Austin Group, despite the fact that its old foe has already fallen out of use. Concerns cited included its dependence on the system-set locale (a global variable subject to multithreading problems) and its support for newer C-language extensions involving wide strings.{{cite web |title=0001122: POSIX should include gettext() and friends - Austin Group Defect Tracker |url=http://austingroupbugs.net/view.php?id=1122 |website=Austin Group Defect Tracker}}

The GNU Project decided that the message-as-key approach of gettext is simpler and more friendly. (Most other systems, including catgets, requires the developer to come up with "key" names for every string.){{cite web |title=The Programmer's View |url=http://ftp.gnu.org/old-gnu/Manuals/gettext-0.10.35/html_chapter/gettext_8.html |website=gettext 0.10.35| date=30 April 1998}} They released GNU gettext, a free software implementation of the system in 1995. Gettext, GNU or not, has since been ported to many programming languages.{{cite web |title=GNU gettext utilities: List of Programming Languages |url=https://www.gnu.org/software/gettext/manual/html_node/List-of-Programming-Languages.html#List-of-Programming-Languages}} The simplicity of po and widespread editor support even lead to its adoption in non-program contexts for text documents or as an intermediate between other localization formats, with converters like po4a (po for anything) and Translate Toolkit emerging to provide such a bridge.{{cite web |title=po4a |url=https://po4a.org/index.php.en |website=po4a.org}}{{cite web |title=The essential toolkit for localization engineers |url=https://toolkit.translatehouse.org/ |website=Translate Toolkit}}

File:Gettext.svg

The basic interface of gettext is the {{code|gettext(const char*)}} function, which accepts a string that the user will see in the original language, usually English. To save typing time and reduce code clutter, this function is commonly aliased to _:{{Cite web |date= |title=GNU gettext utilities: How Marks Appear in Sources |url=https://www.gnu.org/software/gettext/manual/gettext.html#How-Marks-Appear-in-Sources |url-status=live |archive-url=https://web.archive.org/web/20240325095308/https://www.gnu.org/software/gettext/manual/gettext.html#How-Marks-Appear-in-Sources |archive-date=2024-03-25 |access-date=2024-04-03 |website=www.gnu.org}}

printf(gettext("My name is %s.\n"), my_name);

printf(_("My name is %s.\n"), my_name); // same, but shorter

gettext() then uses the supplied strings as keys for looking up translations, and will return the original string when no translation is available. This is in contrast to POSIX catgets(),{{cite web|url=https://www.gnu.org/software/gettext/manual/html_node/catgets.html |website=gnu.org |title=About catgets |access-date=2017-10-24}} AmigaOS GetString(),{{Cite web |title=AmigaOS Manual: Python Modules and Packages - AmigaOS Documentation Wiki |url=https://wiki.amigaos.net/wiki/AmigaOS_Manual:_Python_Modules_and_Packages#GetString.28.29 |access-date=2023-07-09 |website=wiki.amigaos.net}} or Microsoft Windows LoadString() where a programmatic ID (often an integer) is used. To handle the case where the same original-language text can have different meanings, gettext has functions like cgettext() that accept an additional "context" string.

xgettext is run on the sources to produce a .pot (Portable Object Template) file, which contains a list of all the translatable strings extracted from the sources. Comments starting with /// are used to give translators hints, although other prefixes are also configurable to further limit the scope. One such common prefix is TRANSLATORS:.

For example, an input file with a comment might look like:

/// TRANSLATORS: %s contains the user's name as specified in Preferences

printf(_("My name is %s.\n"), my_name);

xgettext is run using the command:

xgettext -c /

The resultant .pot file looks like this with the comment (note that xgettext recognizes the string as a C-language printf format string):

1. . TRANSLATORS: %s contains the user's name as specified in Preferences
2. , c-format
3. : src/name.c:36

msgid "My name is %s.\n"

msgstr ""

In POSIX shell script, gettext provides a gettext.sh library one can include that provides the many same functions gettext provides in similar languages.{{cite web |title=GNU gettext utilities: sh |url=https://www.gnu.org/software/gettext/manual/html_node/sh.html}} GNU bash also has a simplified construct $"msgid" for the simple gettext function, although it depends on the C library to provide a gettext() function.{{cite web |title=GNU gettext utilities: bash |url=https://www.gnu.org/software/gettext/manual/html_node/bash.html}}

The translator derives a .po (Portable Object) file from the template using the msginit program, then fills out the translations.{{cite web|url=https://www.gnu.org/savannah-checkouts/gnu/gettext/manual/html_node/PO-Files.html |title=GNU gettext utilities: PO Files |website=Gnu.org |access-date=2016-04-03}} msginit initializes the translations so, for instance, for a French language translation, the command to run would be:{{cite web|url=http://www.icanlocalize.com/site/tutorials/how-to-translate-with-gettext-po-and-pot-files/ |title=How to Translate With GetText PO and POT Files |website=Icanlocalize.com |access-date=2016-04-03}}

msginit --locale=fr --input=name.pot

This will create fr.po. The translator then edits the resultant file, either by hand or with a translation tool like Poedit, or Emacs with its editing mode for .po files. An edited entry will look like:

1. : src/name.c:36

msgid "My name is %s.\n"

msgstr "Je m'appelle %s.\n"

Finally, the .po files are compiled with msgfmt into binary .mo (Machine Object) files. GNU gettext may use its own file name extension .gmo on systems with another gettext implementation.{{cite web | url=https://www.gnu.org/software/gettext/manual/html_node/Files.html | title=Files Conveying Translations|website=Gnu.org | access-date=2014-04-22}} These are now ready for distribution with the software package.

GNU msgfmt can also perform some checks relevant to the format string used by the programming language. It also allows for outputting to language-specific formats other than MO;{{cite web |title=msgfmt Invocation |url=https://www.gnu.org/software/gettext/manual/html_node/msgfmt-Invocation.html |website=GNU gettext utilities}} the X/Open equivalent is gencat.

In later phases of the developmental workflow, msgmerge can be used to "update" an old translation to a newer template. There is also msgunfmt for reverse-compiling .mo files, and many other utilities for batch processing.

The user, on Unix-type systems, sets the environment variable LC_MESSAGES, and the program will display strings in the selected language, if there is an .mo file for it.

Users on GNU variants can also use the environment variable LANGUAGE instead. Its main difference from the Unix variable is that it supports multiple languages, separated with a colon, for fallback.{{cite web|url=https://www.gnu.org/software/gettext/manual/html_node/Locale-Environment-Variables.html#Locale-Environment-Variables |title=GNU gettext utilities: Locale Environment Variables |website=Gnu.org |access-date=2016-04-03}}

The ngettext() interface accounts for the count of a noun in the string. As with the convention of gettext(), it is often aliased to N_ in practical use. Consider the code sample:

// parameters: english singular, english plural, integer count

printf(ngettext("%d translated message", "%d translated messages", n), n);

A header in the "" (empty string) entry of the PO file stores some metadata, one of which is the plural form that the language uses, usually specified using a C-style ternary operator. Suppose we want to translate for the Slovene language:

msgid ""

msgstr ""

"..."

"Language: sl\n"

"Plural-Forms: nplurals=4; plural=(n%100==1 ? 1 : n%100==2 ? 2 : n%100==3 || n%100==4 ? 3 : 0);\n"

Since now there are four plural forms, the final po would look like:

1. : src/msgfmt.c:876
2. , c-format

msgid "%d translated message"

msgid_plural "%d translated messages"

msgstr[0] "%d prevedenih sporočil"

msgstr[1] "%d prevedeno sporočilo"

msgstr[2] "%d prevedeni sporočili"

msgstr[3] "%d prevedena sporočila"

Reference plural rules for languages are provided by the Unicode consortium.{{cite web |title=Language Plural Rules |url=https://unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html |website=unicode.org}} msginit also prefills the appropriate rule when creating a file for one specific language.

In addition to C, gettext has the following implementations: C# for both ASP.NET{{cite web|url=https://code.google.com/p/gettext-cs-utils/ |title=Google Code Archive - Long-term storage for Google Code Project Hosting |website=Code.google.com |access-date=2016-04-03}}{{cite web|url=https://github.com/turquoiseowl/i18n |title=turquoiseowl/i18n: Smart internationalization for ASP.NET |website=GitHub.com |access-date=2016-04-03}} and for WPF,{{cite web|url=https://github.com/robert-j-engdahl/ngettext-wpf |title=NGettext.Wpf - Proper internationalization support for WPF (via NGettext)|website=GitHub|date=16 August 2019}} Perl,{{cite web|url=https://github.com/gflohr/libintl-perl |title=libintl-perl - An Internationalization Library for Perl That Aims To Be Compatible With the Uniforum Message Translations System as Implemented For Example in GNU Gettext |website=github.com |access-date=2017-09-14}} PHP,{{cite web|url=https://secure.php.net/manual/en/book.gettext.php |title=Gettext |website=php.net |access-date=2017-10-24}} Python,{{cite web|url=https://docs.python.org/library/gettext.html|title=gettext – Multilingual internationalization services – Python 3.7.0 documentation|website=docs.python.org|access-date=2018-09-21}} R,{{Cite web|title=gettext: Translate Text Messages|url=https://rdrr.io/r/base/gettext.html|access-date=2021-11-13|website=rdrr.io|language=en}} Scala,{{cite web|url=https://github.com/makkarpov/scalingua|title=makkarpov/scalingua: A simple gettext-like internationalization library for Scala|website=github.com|access-date=2016-04-28}} and Node.js.{{cite web|url=https://github.com/DanielBaulig/node-gettext |title=DanielBaulig/node-gettext: An adaption of Joshua I. Miller's Javascript Gettext library for node.js |website=GitHub.com |access-date=2016-04-03}}

GNU gettext has native support for Objective-C, but there is no support for the Swift programming language yet. A commonly used gettext implementation on these Cocoa platforms is POLocalizedString.{{cite web |title=hulab/POLocalizedString: gettext for iOS/OS X/watchOS/tvOS |url=https://github.com/hulab/POLocalizedString |website=GitHub |publisher=hulab |date=19 September 2019}} The Microsoft Outlook for iOS team also provides a LocalizedStringsKit library with a gettext-like API.{{cite web |title=microsoft/LocalizedStringKit: Generate .strings files directly from your code |url=https://github.com/microsoft/LocalizedStringKit |website=GitHub |publisher=Microsoft |date=12 February 2020}}

{{Commons category|GNU gettext}}

{{Portal|Free and open-source software}}

• gtranslator
• Poedit
• Translate Toolkit
• Virtaal
• Weblate

{{Reflist}}

• {{official website|https://www.gnu.org/software/gettext/gettext.html|Official GNU gettext site}}

Category:GNU Project software

Category:Internationalization and localization

Category:Software-localization tools