NL_LANGINFO(3POSIX)

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 .