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(), 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 .