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Localization (l10n) and PO files

Once you have internationalized your code by marking translatable strings (see Internationalization (i18n) API), you are ready to start creating translations: this is localization (l10n) of your program, which is achieved by authoring a .po file with a list of translated strings.

In fact, the .po files need not be created by the programmer — they can instead be contributed by users, which allows native speakers of other languages to help you out. There are numerous software tools to help people create and edit .po files, some of which we mention below.

Localization involves three components: setting up the po directory to hold translations, extracting the strings to be translated, and creating/editing .po files for various locales. We summarize each of these components below.

The po directory

Every Julia package or program should set up a po directory to contain its translation files. (For Julia packages, this is typically located in the top level of the package directory, as described in Gettext for modules and packages.) The po directory's location is configured by a call to bindtextdomain in the code (see Domains).

The po directory will initially be empty, but each new localization should add two files:

po/<locale>/LC_MESSAGES/<domain>.po
po/<locale>/LC_MESSAGES/<domain>.mo

  • Here, <locale> is the name of the locale (language and culture) of the localization, typically of the form ll or ll_CC, where ll is the two-letter language code (e.g. en for English or fr for French), and CC is the two-letter code of a country or territory (e.g. en_GB would indicate localization for British English). See also Locale Names in the GNU gettext manual.

  • <domain> is the name of the Gettext domain used by the program or package (see Domains), typically the name of the program or package followed by a unique identifier like a UUID; for a package/module, this is the value of __GETTEXT_DOMAIN__.

  • The <domain>.po file is a human-readable/editable text file containing the translated messages. The <domain>.mo file is a condensed binary representation of the <domain>.po data, which can be generated from <domain>.po by the GNU msgfmt program.

Extracting the strings to be translated

The strings to be translated consist of every call to the localization macros _"...", @ngettext, and so on in the program or package (see Internationalization (i18n) API).

Currently, this list of strings must be extracted manually, but in the near future we hope to automate this process. See: Gettext.jl#22.

Creating/editing .po files

Once a list of strings has been extracted, typically in the form of a "template" .pot file that contains the empty translations (""), there are various ways that you can edit/create .po files:

(We hope that this is a useful list of resources, but currently make no specific recommendations.)