'\" et
.TH NL_LANGINFO "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"
.SH 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.

.SH NAME
nl_langinfo,
nl_langinfo_l
\(em language information
.SH SYNOPSIS
.LP
.nf
#include <langinfo.h>
.P
char *nl_langinfo(nl_item \fIitem\fP);
char *nl_langinfo_l(nl_item \fIitem\fP, locale_t \fIlocale\fP);
.fi
.SH DESCRIPTION
The
\fInl_langinfo\fR()
and
\fInl_langinfo_l\fR()
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
.IR locale ,
respectively (see
.IR <langinfo.h> ).
The manifest constant names and values of
.IR item
are defined in
.IR <langinfo.h> .
For example:
.sp
.RS 4
.nf
\fB
nl_langinfo(ABDAY_1)
.fi \fR
.P
.RE
.P
would return a pointer to the string
.BR \(dqDom\(dq 
if the identified language was Portuguese, and
.BR \(dqSun\(dq 
if the identified language was English.
.sp
.RS 4
.nf
\fB
nl_langinfo_l(ABDAY_1, loc)
.fi \fR
.P
.RE
.P
would return a pointer to the string
.BR \(dqDom\(dq 
if the identified language of the locale represented by
.IR loc
was Portuguese, and
.BR \(dqSun\(dq 
if the identified language of the locale represented by
.IR loc
was English.
.P
The
\fInl_langinfo\fR()
function need not be thread-safe.
.P
The behavior is undefined if the
.IR locale
argument to
\fInl_langinfo_l\fR()
is the special locale object LC_GLOBAL_LOCALE or is not a valid locale
object handle.
.SH "RETURN VALUE"
In a locale where
.IR 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
.IR item
contains an invalid setting.
.P
The application shall not modify the string returned. The pointer
returned by
\fInl_langinfo\fR()
might be invalidated or the string content might be overwritten by a
subsequent call to
\fInl_langinfo\fR()
in any thread or to
\fInl_langinfo_l\fR()
in the same thread or the initial thread, by subsequent calls to
\fIsetlocale\fR()
with a category corresponding to the category of
.IR item
(see
.IR <langinfo.h> )
or the category LC_ALL, or by subsequent calls to
\fIuselocale\fR()
which change the category corresponding to the category of
.IR item .
The pointer returned by
\fInl_langinfo_l\fR()
might be invalidated or the string content might be overwritten by a
subsequent call to
\fInl_langinfo_l\fR()
in the same thread or to
\fInl_langinfo\fR()
in any thread, or by subsequent calls to
\fIfreelocale\fR()
or
\fInewlocale\fR()
which free or modify the locale object that was passed to
\fInl_langinfo_l\fR().
.SH "ERRORS"
No errors are defined.
.br
.LP
.IR "The following sections are informative."
.SH EXAMPLES
.SS "Getting Date and Time Formatting Information"
.P
The following example returns a pointer to a string containing date and
time formatting information, as defined in the
.IR LC_TIME
category of the current locale.
.sp
.RS 4
.nf
\fB
#include <time.h>
#include <langinfo.h>
\&...
strftime(datestring, sizeof(datestring), nl_langinfo(D_T_FMT), tm);
\&...
.fi \fR
.P
.RE
.SH "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.
.SH RATIONALE
The possible interactions between internal data used by
\fInl_langinfo\fR()
and
\fInl_langinfo_l\fR()
are complicated by the fact that
\fInl_langinfo_l\fR()
must be thread-safe but
\fInl_langinfo\fR()
need not be. The various implementation choices are:
.IP " 1." 4
\fInl_langinfo_l\fR()
and
\fInl_langinfo\fR()
use separate buffers, or at least one of them does not use an internal
string buffer. In this case there are no interactions.
.IP " 2." 4
\fInl_langinfo_l\fR()
and
\fInl_langinfo\fR()
share an internal per-thread buffer. There can be interactions, but
only in the same thread.
.IP " 3." 4
\fInl_langinfo_l\fR()
uses an internal per-thread buffer, and
\fInl_langinfo\fR()
uses (in all threads) the same buffer that
\fInl_langinfo_l\fR()
uses in the initial thread. There can be interactions, but only when
\fInl_langinfo_l\fR()
is called in the initial thread.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIsetlocale\fR\^(\|)",
.IR "\fIuselocale\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2008,
.IR "Chapter 7" ", " "Locale",
.IR "\fB<langinfo.h>\fP",
.IR "\fB<locale.h>\fP",
.IR "\fB<nl_types.h>\fP"
.SH 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
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to have been introduced during the conversion of the source files to
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https://www.kernel.org/doc/man-pages/reporting_bugs.html .
