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.\" $OpenBSD: setlocale.3,v 1.21 2018/04/04 14:53:02 schwarze Exp $
.\" $NetBSD: setlocale.3,v 1.3 1997/07/14 23:19:47 kleink Exp $
.\"
.\" Copyright (c) 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Donn Seeley at BSDI.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)setlocale.3 8.1 (Berkeley) 6/9/93
.\"
.Dd $Mdocdate: April 4 2018 $
.Dt SETLOCALE 3
.Os
.Sh NAME
.Nm setlocale
.Nd select character encoding
.Sh SYNOPSIS
.In locale.h
.Ft char *
.Fn setlocale "int category" "const char *locale"
.Sh DESCRIPTION
The
.Fn setlocale
function sets and retrieves the active
.Fa locale
for the current process.
The locale modifies the behaviour of some functions in the C library
with respect to the character encoding, and on other operating systems
also with respect to some language and cultural conventions.
For more information about locales in general, see the
.Xr locale 1
manual page.
.Pp
On
.Ox ,
the only useful value for the
.Fa category
is
.Dv LC_CTYPE .
It sets the locale used for character encoding, character classification,
and case conversion.
For compatibility with natural language support in
.Xr packages 7 ,
all other categories \(em
.Dv LC_COLLATE ,
.Dv LC_MESSAGES ,
.Dv LC_MONETARY ,
.Dv LC_NUMERIC ,
and
.Dv LC_TIME
\(em can be set and retrieved, too, but their values are ignored by the
.Ox
C library.
A category of
.Dv LC_ALL
sets the entire locale generically.
.Pp
The syntax and semantics of the
.Fa locale
argument are not standardized and vary among operating systems.
On
.Ox ,
if the
.Fa locale
string ends with
.Qq ".UTF-8" ,
the UTF-8 locale is selected; otherwise, the
.Qq C
locale is selected, which uses the ASCII character set.
If the
.Fa locale
contains a dot but does not end with
.Qq ".UTF-8" ,
.Fn setlocale
fails.
.Pp
If
.Fa locale
is an empty string
.Pq Qq ,
the value of the environment variable
.Ev LC_ALL ,
with a fallback to the variable corresponding to
.Fa category ,
and with a further fallback to
.Ev LANG ,
is used instead, as documented in the
.Xr locale 1
manual page.
.Pp
If
.Fa locale
is
.Dv NULL ,
the locale remains unchanged.
This can be used to determine the currently active locale.
.Pp
By default, C programs start in the
.Qq C
locale.
The only function in the library that sets the locale is
.Fn setlocale ;
the locale is never changed as a side effect of some other routine.
.Sh RETURN VALUES
In case of success,
.Fn setlocale
returns a pointer to a static string describing the locale
that is in force after the call.
Subsequent calls to
.Fn setlocale
may change the content of the string.
The format of the string is not standardized and varies among
operating systems.
.Pp
On
.Ox ,
if
.Fn setlocale
was never called with a
.Pf non- Dv NULL
.Fa locale
argument, the string
.Qq C
is returned.
Otherwise, if the
.Fa category
was not
.Dv LC_ALL
or if the locale is the same for all categories, a copy of the
.Fa locale
argument is returned.
Otherwise, the locales for the six categories
.Dv LC_COLLATE ,
.Dv LC_CTYPE ,
.Dv LC_MESSAGES ,
.Dv LC_MONETARY ,
.Dv LC_NUMERIC ,
.Dv LC_TIME
are concatenated in that order, with slash
.Pq Ql /
characters in between.
.Pp
In case of failure,
.Fn setlocale
returns
.Dv NULL .
On
.Ox ,
that can only happen if the
.Fa category
is invalid, if a character encoding other than UTF-8 is requested,
if the requested
.Fa locale
name is of excessive length, or if memory allocation fails.
.Sh EXAMPLES
Calling
.Pp
.Dl setlocale(LC_CTYPE, \(dqen_US.UTF-8\(dq);
.Pp
at the beginning of a program selects the UTF-8 locale and returns
.Qq en_US.UTF-8 .
Calling
.Pp
.Dl setlocale(LC_ALL, NULL);
.Pp
right afterwards leaves the locale unchanged and returns
.Qq C/en_US.UTF-8/C/C/C/C .
.Sh STANDARDS
The
.Fn setlocale
function conforms to
.St -ansiC .
.Sh HISTORY
The
.Fn setlocale
function first appeared in
.Bx 4.4 .
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