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gettext grok
To fully exploit the functionality of the GNU 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:
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 gettext
function. The method which is presented here only works correctly
with the GNU implementation of the gettext functions.
In the function 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:
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, LANGUAGE changes. According
to the process explained above the new value of this variable is found
as soon as the 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 dcgettext function as long as no new catalog is loaded. But
if dcgettext is not called the program also cannot find the
LANGUAGE variable be changed (see section 10.2.7 Optimization of the *gettext functions). A
solution for this is very easy. Include the following code in the
language switching function.
/* Change language. */
setenv ("LANGUAGE", "fr", 1);
/* Make change known. */
{
extern int _nl_msg_cat_cntr;
++_nl_msg_cat_cntr;
}
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The variable _nl_msg_cat_cntr is defined in `loadmsgcat.c'.
You don't need to know what this is for. But it can be used to detect
whether a gettext implementation is GNU gettext and not non-GNU
system's native gettext implementation.
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