The facilities in GNU
gettext focus on messages; strings printed
by a program, either directly or via formatting with
When using GNU
gettext, each application has its own
text domain. This is a unique name, such as ‘kpilot’ or ‘gawk’,
that identifies the application.
A complete application may have multiple components—programs written
in C or C++, as well as scripts written in
All of the components use the same text domain.
To make the discussion concrete, assume we’re writing an application
guide. Internationalization consists of the
following steps, in this order:
guide’s components and marks each string that is a candidate for translation. For example,
"`-F': option required"is a good candidate for translation. A table with strings of option names is not (e.g.,
gawk’s --profile option should remain the same, no matter what the local language).
"guide") to the
gettextlibrary, by calling the
.po) and translations are created and shipped with the application. For example, there might be a fr.po for a French translation.
guideis built and installed, the binary translation files are installed in a standard place.
gettextto use .gmo files in a different directory than the standard one by using the
guidelooks up each string via a call to
gettext(). The returned string is the translated string if available, or the original string if not.
In C (or C++), the string marking and dynamic translation lookup
are accomplished by wrapping each string in a call to
printf("%s", gettext("Don't Panic!\n"));
The tools that extract messages from source code pull out all
strings enclosed in calls to
gettext developers, recognizing that typing
‘gettext(…)’ over and over again is both painful and ugly to look
at, use the macro ‘_’ (an underscore) to make things easier:
/* In the standard header file: */ #define _(str) gettext(str) /* In the program text: */ printf("%s", _("Don't Panic!\n"));
This reduces the typing overhead to just three extra characters per string and is considerably easier to read as well.
There are locale categories
for different types of locale-related information.
The defined locale categories that
gettext knows about are:
Text messages. This is the default category for
operations, but it is possible to supply a different one explicitly,
if necessary. (It is almost never necessary to supply a different category.)
Text-collation information; i.e., how different characters and/or groups of characters sort in a given language.
Character-type information (alphabetic, digit, upper- or lowercase, and
This information is accessed via the
POSIX character classes in regular expressions,
(see Regexp Operators).
Monetary information, such as the currency symbol, and whether the symbol goes before or after a number.
Numeric information, such as which characters to use for the decimal point and the thousands separator.83
Response information, such as how “yes” and “no” appear in the local language, and possibly other information as well.
Time- and date-related information, such as 12- or 24-hour clock, month printed before or after the day in a date, local month abbreviations, and so on.
All of the above. (Not too useful in the context of
For some operating systems, the
port doesn’t support GNU
Therefore, these features are not available
if you are using one of those operating systems. Sorry.
Americans use a comma every three decimal places and a period for the decimal point, while many Europeans do exactly the opposite: 1,234.56 versus 1.234,56.