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(libc.info)Locale Information

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Accessing Locale Information
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   There are several ways to access locale information.  The simplest
way is to let the C library itself do the work.  Several of the
functions in this library implicitly access the locale data, and use
what information is provided by the currently selected locale.  This is
how the locale model is meant to work normally.

   As an example take the `strftime' function, which is meant to nicely
format date and time information (Note: Formatting Calendar Time).
Part of the standard information contained in the `LC_TIME' category is
the names of the months.  Instead of requiring the programmer to take
care of providing the translations the `strftime' function does this
all by itself.  `%A' in the format string is replaced by the
appropriate weekday name of the locale currently selected by `LC_TIME'.
This is an easy example, and wherever possible functions do things
automatically in this way.

   But there are quite often situations when there is simply no function
to perform the task, or it is simply not possible to do the work
automatically.  For these cases it is necessary to access the
information in the locale directly.  To do this the C library provides
two functions: `localeconv' and `nl_langinfo'.  The former is part of
ISO C and therefore portable, but has a brain-damaged interface.  The
second is part of the Unix interface and is portable in as far as the
system follows the Unix standards.

The Lame Way to Locale Data

ISO C's `localeconv'.

The Elegant and Fast Way

X/Open's `nl_langinfo'.