nl_langinfo(3p) — Linux manual page

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

PROLOG

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

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(3p), uselocale(3p)

       The Base Definitions volume of POSIX.1‐2017, Chapter 7, Locale,
       langinfo.h(0p), locale.h(0p), nl_types.h(0p)

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(3P)

Pages that refer to this page: langinfo.h(0p), nl_types.h(0p), localeconv(3p), setlocale(3p)

---