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(standards.info)Internationalization

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Internationalization
====================

   GNU has a library called GNU gettext that makes it easy to translate
the messages in a program into various languages.  You should use this
library in every program.  Use English for the messages as they appear
in the program, and let gettext provide the way to translate them into
other languages.

   Using GNU gettext involves putting a call to the `gettext' macro
around each string that might need translation--like this:

     printf (gettext ("Processing file `%s'..."));

This permits GNU gettext to replace the string `"Processing file
`%s'..."' with a translated version.

   Once a program uses gettext, please make a point of writing calls to
`gettext' when you add new strings that call for translation.

   Using GNU gettext in a package involves specifying a "text domain
name" for the package.  The text domain name is used to separate the
translations for this package from the translations for other packages.
Normally, the text domain name should be the same as the name of the
package--for example, `fileutils' for the GNU file utilities.

   To enable gettext to work well, avoid writing code that makes
assumptions about the structure of words or sentences.  When you want
the precise text of a sentence to vary depending on the data, use two or
more alternative string constants each containing a complete sentences,
rather than inserting conditionalized words or phrases into a single
sentence framework.

   Here is an example of what not to do:

     printf ("%d file%s processed", nfiles,
             nfiles != 1 ? "s" : "");

The problem with that example is that it assumes that plurals are made
by adding `s'.  If you apply gettext to the format string, like this,

     printf (gettext ("%d file%s processed"), nfiles,
             nfiles != 1 ? "s" : "");

the message can use different words, but it will still be forced to use
`s' for the plural.  Here is a better way:

     printf ((nfiles != 1 ? "%d files processed"
              : "%d file processed"),
             nfiles);

This way, you can apply gettext to each of the two strings
independently:

     printf ((nfiles != 1 ? gettext ("%d files processed")
              : gettext ("%d file processed")),
             nfiles);

This can be any method of forming the plural of the word for "file", and
also handles languages that require agreement in the word for
"processed".

   A similar problem appears at the level of sentence structure with
this code:

     printf ("#  Implicit rule search has%s been done.\n",
             f->tried_implicit ? "" : " not");

Adding `gettext' calls to this code cannot give correct results for all
languages, because negation in some languages requires adding words at
more than one place in the sentence.  By contrast, adding `gettext'
calls does the job straightfowardly if the code starts out like this:

     printf (f->tried_implicit
             ? "#  Implicit rule search has been done.\n",
             : "#  Implicit rule search has not been done.\n");