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.\" and 1999 by Bruno Haible (haible@clisp.cons.org)
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.\" Modified Sat Jul 24 18:20:12 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified Tue Jul 15 16:49:10 1997 by Andries Brouwer (aeb@cwi.nl)
.\" Modified Sun Jul  4 14:52:16 1999 by Bruno Haible (haible@clisp.cons.org)
.\" Modified Tue Aug 24 17:11:01 1999 by Andries Brouwer (aeb@cwi.nl)
.\"
.TH SETLOCALE 3  "July 4, 1999" "GNU" "Linux Programmer's Manual"
.SH NAME
setlocale \- set the current locale.
.SH SYNOPSIS
.nf
.B #include <locale.h>
.sp
.BI "char *setlocale(int " category ", const char * " locale ");"
.fi
.SH DESCRIPTION
The 
.B setlocale()
function is used to set or query the program's current locale.
.PP
If
.I locale
is not
.BR NULL ,
the program's current locale is modified according to the arguments.
The argument
.I category
determines which parts of the program's current locale should be modified.
.TP
.B LC_ALL
for all of the locale.
.TP
.B LC_COLLATE
for regular expression matching (it determines the meaning
of range expressions and equivalence classes) and string collation.
.TP
.B LC_CTYPE
for regular expression matching, character classification, conversion,
case-sensitive comparison, and wide character functions.
.TP
.B LC_MESSAGES
for localizable natural-language messages.
.TP
.B LC_MONETARY
for monetary formatting.
.TP
.B LC_NUMERIC
for number formatting (such as the decimal point and the thousands separator).
.TP
.B LC_TIME
for time and date formatting.
.PP
The argument
.I locale
is a pointer to a character string containing the
required setting of
.IR category .
Such a string is either a well-known constant like "C" or "da_DK"
(see below), or an opaque string that was returned by another call of
.BR setlocale .
.PP
If
.I locale
is
.BR """""" ,
each part of the locale that should be modified is set according to the
environment variables. The details are implementation dependent.
For glibc, first
.\" [This is false on my system - must check which library versions do this]
.\" if
.\" .I category
.\" is LC_MESSAGES, the environment variable LANGUAGE is inspected,
.\" then
(regardless of
.IR category ),
the environment variable LC_ALL is inspected,
next the environment variable with the same name as the category
(LC_COLLATE, LC_CTYPE, LC_MESSAGES, LC_MONETARY, LC_NUMERIC, LC_TIME)
and finally the environment variable LANG.
The first existing environment variable is used.
If its value is not a valid locale specification, the locale
is unchanged, and
.B setlocale
returns NULL.
.\" The environment variable LANGUAGE may contain several, colon-separated,
.\" locale names.
.PP
The locale
.B """C"""
or
.B """POSIX"""
is a portable locale; its LC_CTYPE part corresponds to the 7-bit ASCII
character set.
.PP
A locale name is typically of the form
.IR language "[_" territory "][." codeset "][@" modifier "],"
where
.I language
is an ISO 639 language code,
.I territory
is an ISO 3166 country code, and
.I codeset
is a character set or encoding identifier like
.B "ISO-8859-1"
or
.BR "UTF-8" .
.PP
If
.I locale
is
.BR NULL ,
the current locale is only queried, not modified.
.PP
On startup of the main program, the portable
.B """C"""
locale is selected as default.
A program may be made portable to all locales by calling
.B setlocale(LC_ALL, """""")
after program  initialization, by using the values returned
from a
.B localeconv()
call
for locale \- dependent information, by using the multi-byte and wide
character functions for text processing if
.BR "MB_CUR_MAX > 1" ,
and by using
.BR strcoll() ", " wstrcoll()
or 
.BR strxfrm() ", " wstrxfrm()
to compare strings.
.SH "RETURN VALUE"
A successful call to
.B setlocale()
returns a string that corresponds to the locale set.
This string may be allocated in static storage.
The string returned is such that a subsequent call with that string
and its associated category will restore that part of the process's
locale. The return value is
.B NULL
if the request cannot be honored.
.SH "CONFORMING TO"
ANSI C, POSIX.1
.SH NOTES
Linux (that is, GNU libc) supports the portable locales
.BR """C""" " and " """POSIX""" .
In the good old days there used to be support for
the European Latin-1 
.B """ISO-8859-1"""
locale (e.g. in libc-4.5.21 and libc-4.6.27), and the Russian
.B """KOI-8"""
(more precisely, "koi-8r") locale (e.g. in libc-4.6.27),
so that having an environment variable LC_CTYPE=ISO-8859-1
sufficed to make isprint() return the right answer.
These days non-English speaking Europeans have to work a bit harder,
and must install actual locale files.
.SH "SEE ALSO"
.BR locale (1),
.BR localedef (1),
.BR strcoll (3),
.BR isalpha (3),
.BR localeconv (3),
.BR strftime (3),
.BR charsets (4),
.BR locale (7)