NL_LANGINFO
Section: POSIX Programmer's Manual (3P)
Updated: 2017
Page Index
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
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