326 lines
7.8 KiB
Groff
326 lines
7.8 KiB
Groff
.\" $OpenBSD: setlocale.3,v 1.24 2022/08/04 06:20:24 jsg Exp $
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.\" $NetBSD: setlocale.3,v 1.3 1997/07/14 23:19:47 kleink Exp $
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.\"
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.\" Copyright (c) 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Donn Seeley at BSDI.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)setlocale.3 8.1 (Berkeley) 6/9/93
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.\"
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.Dd $Mdocdate: August 4 2022 $
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.Dt SETLOCALE 3
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.Os
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.Sh NAME
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.Nm setlocale
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.Nd select character encoding
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.Sh SYNOPSIS
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.In locale.h
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.Ft char *
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.Fn setlocale "int category" "const char *locale"
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.Sh DESCRIPTION
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The
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.Fn setlocale
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function sets and retrieves the active
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.Fa locale
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for the current process.
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The locale modifies the behaviour of some functions in the C library
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with respect to the character encoding, and on other operating systems
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also with respect to some language and cultural conventions.
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For more information about locales in general, see the
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.Xr locale 1
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manual page.
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.Pp
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On
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.Ox ,
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the only useful value for the
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.Fa category
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is
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.Dv LC_CTYPE .
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It sets the locale used for character encoding, character classification,
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and case conversion.
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For compatibility with natural language support in
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.Xr packages 7 ,
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all other categories \(em
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.Dv LC_COLLATE ,
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.Dv LC_MESSAGES ,
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.Dv LC_MONETARY ,
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.Dv LC_NUMERIC ,
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and
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.Dv LC_TIME
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\(em can be set and retrieved, too, but their values are ignored by the
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.Ox
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C library.
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A category of
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.Dv LC_ALL
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sets the entire locale generically, which is strongly discouraged for
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security reasons in portable programs.
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.Pp
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The syntax and semantics of the
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.Fa locale
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argument are not standardized and vary among operating systems.
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On
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.Ox ,
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if the
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.Fa locale
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string ends with
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.Qq ".UTF-8" ,
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the UTF-8 locale is selected; otherwise, the
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.Qq C
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locale is selected, which uses the ASCII character set.
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If the
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.Fa locale
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contains a dot but does not end with
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.Qq ".UTF-8" ,
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.Fn setlocale
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fails.
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.Pp
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If
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.Fa locale
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is an empty string
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.Pq Qq ,
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the value of the environment variable
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.Ev LC_ALL ,
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with a fallback to the variable corresponding to
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.Fa category ,
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and with a further fallback to
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.Ev LANG ,
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is used instead, as documented in the
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.Xr locale 1
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manual page.
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.Pp
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If
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.Fa locale
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is
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.Dv NULL ,
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the locale remains unchanged.
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This can be used to determine the currently active locale.
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.Pp
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By default, C programs start in the
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.Qq C
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locale.
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The only function in the library that sets the locale is
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.Fn setlocale ;
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the locale is never changed as a side effect of some other routine.
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.Pp
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The
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.Dv LC_CTYPE
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category modifies the behaviour of at least the following functions:
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.Xr iswctype 3 ,
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.Xr mblen 3 ,
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.Xr mbrlen 3 ,
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.Xr mbrtowc 3 ,
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.Xr mbsrtowcs 3 ,
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.Xr mbstowcs 3 ,
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.Xr mbtowc 3 ,
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.Xr towctrans 3 ,
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.Xr towlower 3 ,
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.Xr towupper 3 ,
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.Xr wcrtomb 3 ,
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.Xr wcscasecmp 3 ,
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.Xr wcsrtombs 3 ,
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.Xr wcstombs 3 ,
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.Xr wctomb 3 ,
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.Xr wctrans 3 ,
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.Xr wctype 3 ,
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and the functions documented in
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.Xr iswalnum 3 .
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.Sh RETURN VALUES
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In case of success,
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.Fn setlocale
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returns a pointer to a static string describing the locale
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that is in force after the call.
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Subsequent calls to
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.Fn setlocale
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may change the content of the string.
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The format of the string is not standardized and varies among
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operating systems.
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.Pp
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On
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.Ox ,
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if
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.Fn setlocale
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was never called with a
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.Pf non- Dv NULL
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.Fa locale
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argument, the string
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.Qq C
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is returned.
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Otherwise, if the
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.Fa category
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was not
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.Dv LC_ALL
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or if the locale is the same for all categories, a copy of the
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.Fa locale
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argument is returned.
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Otherwise, the locales for the six categories
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.Dv LC_COLLATE ,
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.Dv LC_CTYPE ,
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.Dv LC_MESSAGES ,
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.Dv LC_MONETARY ,
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.Dv LC_NUMERIC ,
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.Dv LC_TIME
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are concatenated in that order, with slash
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.Pq Ql /
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characters in between.
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.Pp
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In case of failure,
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.Fn setlocale
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returns
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.Dv NULL .
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On
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.Ox ,
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that can only happen if the
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.Fa category
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is invalid, if a character encoding other than UTF-8 is requested,
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if the requested
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.Fa locale
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name is of excessive length, or if memory allocation fails.
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.Sh EXAMPLES
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Calling
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.Pp
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.Dl setlocale(LC_CTYPE, \(dqen_US.UTF-8\(dq);
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.Pp
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at the beginning of a program selects the UTF-8 locale and returns
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.Qq en_US.UTF-8 .
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Calling
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.Pp
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.Dl setlocale(LC_ALL, NULL);
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.Pp
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right afterwards leaves the locale unchanged and returns
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.Qq C/en_US.UTF-8/C/C/C/C .
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.Sh SEE ALSO
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.Xr locale 1 ,
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.Xr newlocale 3 ,
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.Xr nl_langinfo 3 ,
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.Xr uselocale 3
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.Sh STANDARDS
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The
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.Fn setlocale
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function conforms to
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.St -ansiC .
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.Sh HISTORY
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The
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.Fn setlocale
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function first appeared in
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.Bx 4.3 Net/2 .
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.Sh CAVEATS
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On systems other than
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.Ox ,
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calling
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.Fn setlocale
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or
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.Xr uselocale 3
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with a
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.Fa category
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other than
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.Dv LC_CTYPE
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can cause erratic behaviour of many library functions.
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For security reasons, make sure that portable programs only use
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.Dv LC_CTYPE .
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.Pp
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For example, the following functions may be affected.
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The list is probably incomplete.
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For example, additional library functions may be impacted
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if they directly or indirectly call affected functions,
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or if they attempt to imitate aspects of their behaviour.
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Functions that are not standardized may be affected too.
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.Bl -tag -width Ds
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.It Dv LC_COLLATE
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.Xr glob 3 ,
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.Xr strcoll 3 ,
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.Xr strxfrm 3 ,
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.Xr wcscoll 3 ,
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.Xr wcsxfrm 3 ,
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and the functions documented in
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.Xr regexec 3
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.It Dv LC_MESSAGES
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.Xr catgets 3 ,
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.Xr catopen 3 ,
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.Xr nl_langinfo 3 ,
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.Xr perror 3 ,
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.Xr psignal 3 ,
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.Xr strerror 3 ,
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.Xr strsignal 3 ,
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and the functions documented in
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.Xr err 3
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.It Dv LC_MONETARY
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.Xr localeconv 3 ,
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.Xr nl_langinfo 3 ,
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.Fn strfmon
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.It Dv LC_NUMERIC
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.Xr atof 3 ,
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.Xr localeconv 3 ,
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.Xr nl_langinfo 3 ,
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.Fn strfmon ,
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and the functions documented in
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.Xr printf 3 ,
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.Xr scanf 3 ,
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.Xr strtod 3 ,
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.Xr wcstod 3 ,
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.Xr wprintf 3 ,
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.Xr wscanf 3 .
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This category is particularly dangerous because it can cause bugs
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in the parsing and formatting of numbers, for example failures to
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recognize or properly write decimal points.
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.It Dv LC_TIME
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.Fn getdate ,
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.Xr nl_langinfo 3 ,
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.Xr strftime 3 ,
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.Xr strptime 3 .
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Similarly, this is prone to causing bugs in the parsing and formatting
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of date strings.
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.It Dv LC_CTYPE
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On systems other than
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.Ox ,
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this category may affect the behaviour of additional functions,
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for example:
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.Xr btowc 3 ,
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.Xr isalnum 3 ,
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.Xr isalpha 3 ,
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.Xr isblank 3 ,
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.Xr iscntrl 3 ,
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.Xr isdigit 3 ,
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.Xr isgraph 3 ,
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.Xr islower 3 ,
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.Xr isprint 3 ,
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.Xr ispunct 3 ,
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.Xr isspace 3 ,
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.Xr isupper 3 ,
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.Xr isxdigit 3 ,
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.Xr mbsinit 3 ,
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.Xr strcasecmp 3 ,
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.Xr strcoll 3 ,
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.Xr strxfrm 3 ,
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.Xr tolower 3 ,
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.Xr toupper 3 ,
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.Xr vis 3 ,
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.Xr wcscoll 3 ,
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.Xr wcsxfrm 3 ,
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.Xr wctob 3
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.El
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