NL_LANGINFO(3)             POSIX Programmer's Manual            NL_LANGINFO(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       nl_langinfo, nl_langinfo_l -- language information

SYNOPSIS
       #include <langinfo.h>

       char *nl_langinfo(nl_item item);
       char *nl_langinfo_l(nl_item item, locale_t locale);

DESCRIPTION
       The nl__langinfo() and nl__langinfo___l() functions shall return a pointer
       to a string containing information relevant to the particular language
       or cultural area defined in the current locale, or in the locale
       represented by locale, respectively (see <langinfo.h>).  The manifest
       constant names and values of item are defined in <langinfo.h>.  For
       example:


           nl_langinfo(ABDAY_1)

       would return a pointer to the string "Dom" if the identified language
       was Portuguese, and "Sun" if the identified language was English.


           nl_langinfo_l(ABDAY_1, loc)

       would return a pointer to the string "Dom" if the identified language
       of the locale represented by loc was Portuguese, and "Sun" if the
       identified language of the locale represented by loc was English.

       The nl__langinfo() function need not be thread-safe.

       The behavior is undefined if the locale argument to nl__langinfo___l() is
       the special locale object LC_GLOBAL_LOCALE or is not a valid locale
       object handle.

RETURN VALUE
       In a locale where langinfo data is not defined, these functions shall
       return a pointer to the corresponding string in the POSIX locale. In
       all locales, these functions shall return a pointer to an empty string
       if item contains an invalid setting.

       The application shall not modify the string returned. The pointer
       returned by nl__langinfo() might be invalidated or the string content
       might be overwritten by a subsequent call to nl__langinfo() in any
       thread or to nl__langinfo___l() in the same thread or the initial thread,
       by subsequent calls to setlocale() with a category corresponding to the
       category of item (see <langinfo.h>) or the category LC_ALL, or by
       subsequent calls to uselocale() which change the category corresponding
       to the category of item.  The pointer returned by nl__langinfo___l() might
       be invalidated or the string content might be overwritten by a
       subsequent call to nl__langinfo___l() in the same thread or to
       nl__langinfo() in any thread, or by subsequent calls to freelocale() or
       newlocale() which free or modify the locale object that was passed to
       nl__langinfo___l().  The returned pointer and the string content might
       also be invalidated if the calling thread is terminated.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
   Getting Date and Time Formatting Information
       The following example returns a pointer to a string containing date and
       time formatting information, as defined in the LC__TIME category of the
       current locale.


           #include <time.h>
           #include <langinfo.h>
           ...
           strftime(datestring, sizeof(datestring), nl_langinfo(D_T_FMT), tm);
           ...

APPLICATION USAGE
       The array pointed to by the return value should not be modified by the
       program, but may be modified by further calls to these functions.

RATIONALE
       The possible interactions between internal data used by nl__langinfo()
       and nl__langinfo___l() are complicated by the fact that nl__langinfo___l()
       must be thread-safe but nl__langinfo() need not be. The various
       implementation choices are:

        1. nl__langinfo___l() and nl__langinfo() use separate buffers, or at least
           one of them does not use an internal string buffer. In this case
           there are no interactions.

        2. nl__langinfo___l() and nl__langinfo() share an internal per-thread
           buffer. There can be interactions, but only in the same thread.

        3. nl__langinfo___l() uses an internal per-thread buffer, and
           nl__langinfo() uses (in all threads) the same buffer that
           nl__langinfo___l() uses in the initial thread. There can be
           interactions, but only when nl__langinfo___l() is called in the
           initial thread.

FUTURE DIRECTIONS
       None.

SEE ALSO
       setlocale(), uselocale()

       The Base Definitions volume of POSIX.1-2017, Chapter _7, Locale,
       <langinfo.h>, <locale.h>, <nl_types.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                       NL_LANGINFO(3)
