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().

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.1‐2008, 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,  2013  Edition,  Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013  by  the
       Institute  of  Electrical  and  Electronics  Engineers,  Inc and The Open Group.  (This is
       POSIX.1-2008 with the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/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 .