man3/nl_langinfo.3

.\" Copyright (c) 2001 Markus Kuhn <mkuhn@acm.org>
.\" and Copyright (c) 2015 Sam Varshavchik <mrsam@courier-mta.com>
.\" and Copyright (c) 2015 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
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.\" References consulted:
.\"   GNU glibc-2 manual
.\"   OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html
.\"
.\" Corrected prototype, 2002-10-18, aeb
.\"
.TH NL_LANGINFO 3  2021-03-22 "GNU" "Linux Programmer's Manual"
.SH NAME
nl_langinfo, nl_langinfo_l \- query language and locale information
.SH SYNOPSIS
.nf
.B #include <langinfo.h>
.PP
.BI "char *nl_langinfo(nl_item " item );
.BI "char *nl_langinfo_l(nl_item " item ", locale_t " locale );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR nl_langinfo_l ():
.nf
    Since glibc 2.24:
        _POSIX_C_SOURCE >= 200809L
    Glibc 2.23 and earlier:
        _POSIX_C_SOURCE >= 200112L
.fi
.SH DESCRIPTION
The
.BR nl_langinfo ()
and
.BR nl_langinfo_l ()
functions provide access to locale information
in a more flexible way than
.BR localeconv (3).
.BR nl_langinfo ()
returns a string which is the value corresponding to
\fIitem\fP in the program's current global
locale.
.BR nl_langinfo_l ()
returns a string which is the value corresponding to \fIitem\fP
for the locale identified by the locale object \fIlocale\fP,
which was previously created by
.BR newlocale (3).
Individual and additional elements of the locale categories can
be queried.
.PP
Examples for the locale elements that can be specified in \fIitem\fP
using the constants defined in \fI<langinfo.h>\fP are:
.TP
.BR CODESET \ (LC_CTYPE)
Return a string with the name of the character encoding used in the
selected locale, such as "UTF-8", "ISO-8859-1", or "ANSI_X3.4-1968"
(better known as US-ASCII).
This is the same string that you get with
"locale charmap".
For a list of character encoding names,
try "locale \-m" (see
.BR locale (1)).
.TP
.BR D_T_FMT \ (LC_TIME)
Return a string that can be used as a format string for
.BR strftime (3)
to represent time and date in a locale-specific way
.RB ( %c
conversion specification).
.TP
.BR D_FMT \ (LC_TIME)
Return a string that can be used as a format string for
.BR strftime (3)
to represent a date in a locale-specific way
.RB ( %x
conversion specification).
.TP
.BR T_FMT \ (LC_TIME)
Return a string that can be used as a format string for
.BR strftime (3)
to represent a time in a locale-specific way
.RB ( %X
conversion specification).
.TP
.BR AM_STR \ (LC_TIME)
Return a string that represents affix for ante meridiem (before noon, "AM")
time.
(Used in
.B %p
.BR strftime (3)
conversion specification.)
.TP
.BR PM_STR \ (LC_TIME)
Return a string that represents affix for post meridiem (before midnight, "PM")
time.
(Used in
.B %p
.BR strftime (3)
conversion specification.)
.TP
.BR T_FMT_AMPM \ (LC_TIME)
Return a string that can be used as a format string for
.BR strftime (3)
to represent a time in a.m. or p.m. notation a locale-specific way
.RB ( %r
conversion specification).
.TP
.BR ERA \ (LC_TIME)
Return era description, which contains information about how years are counted
and displayed for each era in a locale.
Each era description segment shall have the format:
.RS
.IP
.IR direction : offset : start_date : end_date : era_name : era_format
.RE
.IP
according to the definitions below:
.RS
.TP 12
.I direction
Either a
.RB \[dq] + "\[dq] or a \[dq]" - \[dq]
character.
The
.RB \[dq] + \[dq]
means that years increase from the
.I start_date
towards the
.IR end_date ,
.RB \[dq] - \[dq]
means the opposite.
.TP
.I offset
The epoch year of the
.IR start_date .
.TP
.I start_date
A date in the form
.IR yyyy / mm / dd ,
where
.IR yyyy ", " mm ", and " dd
are the year, month, and day numbers respectively of the start of the era.
.TP
.I end_date
The ending date of the era, in the same format as the
.IR start_date ,
or one of the two special values
.RB \[dq] -* \[dq]
(minus infinity) or
.RB \[dq] +* \[dq]
(plus infinity).
.TP
.I era_name
The name of the era, corresponding to the
.B %EC
.BR strftime (3)
conversion specification.
.TP
.I era_format
The format of the year in the era, corresponding to the
.B %EY
.BR strftime (3)
conversion specification.
.RE
.IP
Era description segments are separated by semicolons.
Most locales do not define this value.
Examples of locales that do define this value are the Japanese and Thai
locales.
.TP
.BR ERA_D_T_FMT \ (LC_TIME)
Return a string that can be used as a format string for
.BR strftime (3)
for alternative representation of time and date in a locale-specific way
.RB ( %Ec
conversion specification).
.TP
.BR ERA_D_FMT \ (LC_TIME)
Return a string that can be used as a format string for
.BR strftime (3)
for alternative representation of a date in a locale-specific way
.RB ( %Ex
conversion specification).
.TP
.BR ERA_T_FMT \ (LC_TIME)
Return a string that can be used as a format string for
.BR strftime (3)
for alternative representation of a time in a locale-specific way
.RB ( %EX
conversion specification).
.TP
.BR DAY_ "{1\(en7} (LC_TIME)"
Return name of the \fIn\fP-th day of the week. [Warning: this follows
the US convention DAY_1 = Sunday, not the international convention
(ISO 8601) that Monday is the first day of the week.]
(Used in
.B %A
.BR strftime (3)
conversion specification.)
.TP
.BR ABDAY_ "{1\(en7} (LC_TIME)"
Return abbreviated name of the \fIn\fP-th day of the week.
(Used in
.B %a
.BR strftime (3)
conversion specification.)
.TP
.BR MON_ "{1\(en12} (LC_TIME)"
Return name of the \fIn\fP-th month.
(Used in
.B %B
.BR strftime (3)
conversion specification.)
.TP
.BR ABMON_ "{1\(en12} (LC_TIME)"
Return abbreviated name of the \fIn\fP-th month.
(Used in
.B %b
.BR strftime (3)
conversion specification.)
.TP
.BR RADIXCHAR \ (LC_NUMERIC)
Return radix character (decimal dot, decimal comma, etc.).
.TP
.BR THOUSEP \ (LC_NUMERIC)
Return separator character for thousands (groups of three digits).
.TP
.BR YESEXPR \ (LC_MESSAGES)
Return a regular expression that can be used with the
.BR regex (3)
function to recognize a positive response to a yes/no question.
.TP
.BR NOEXPR \ (LC_MESSAGES)
Return a regular expression that can be used with the
.BR regex (3)
function to recognize a negative response to a yes/no question.
.TP
.BR CRNCYSTR \ (LC_MONETARY)
Return the currency symbol, preceded by "\-" if the symbol should
appear before the value, "+" if the symbol should appear after the
value, or "." if the symbol should replace the radix character.
.PP
The above list covers just some examples of items that can be requested.
For a more detailed list, consult
.IR "The GNU C Library Reference Manual" .
.SH RETURN VALUE
On success, these functions return a pointer to a string which
is the value corresponding to
.I item
in the specified locale.
.PP
If no locale has been selected by
.BR setlocale (3)
for the appropriate category,
.BR nl_langinfo ()
return a pointer to the corresponding string in the "C" locale.
The same is true of
.BR nl_langinfo_l ()
if
.I locale
specifies a locale where
.I langinfo
data is not defined.
.PP
If \fIitem\fP is not valid, a pointer to an empty string is returned.
.PP
The pointer returned by these functions may point to static data that
may be overwritten, or the pointer itself may be invalidated,
by a subsequent call to
.BR nl_langinfo (),
.BR nl_langinfo_l (),
or
.BR setlocale (3).
The same statements apply to
.BR nl_langinfo_l ()
if the locale object referred to by
.I locale
is freed or modified by
.BR freelocale (3)
or
.BR newlocale (3).
.PP
POSIX specifies that the application may not modify
the string returned by these functions.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR nl_langinfo ()
T}	Thread safety	MT-Safe locale
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SUSv2.
.SH NOTES
The behavior of
.BR nl_langinfo_l ()
is undefined if
.I locale
is the special locale object
.BR LC_GLOBAL_LOCALE
or is not a valid locale object handle.
.SH EXAMPLES
The following program sets the character type and the numeric locale
according to the environment and queries the terminal character set and
the radix character.
.PP
.EX
#include <langinfo.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char *argv[])
{
    setlocale(LC_CTYPE, "");
    setlocale(LC_NUMERIC, "");

    printf("%s\en", nl_langinfo(CODESET));
    printf("%s\en", nl_langinfo(RADIXCHAR));

    exit(EXIT_SUCCESS);
}
.EE
.SH SEE ALSO
.BR locale (1),
.BR localeconv (3),
.BR setlocale (3),
.BR charsets (7),
.BR locale (7)
.PP
The GNU C Library Reference Manual