SETLOCALE(3P) POSIX Programmer's Manual SETLOCALE(3P)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.
NAMEsetlocale — set program locale
SYNOPSIS
#include <locale.h>
char *setlocale(int category, const char *locale);
DESCRIPTION
The functionality described on this reference page is aligned with the
ISO C standard. Any conflict between the requirements described here
and the ISO C standard is unintentional. This volume of POSIX.1‐2008
defers to the ISO C standard.
The setlocale() function selects the appropriate piece of the global
locale, as specified by the category and locale arguments, and can be
used to change or query the entire global locale or portions thereof.
The value LC_ALL for category names the entire global locale; other
values for category name only a part of the global locale:
LC_COLLATE Affects the behavior of regular expressions and the colla‐
tion functions.
LC_CTYPE Affects the behavior of regular expressions, character
classification, character conversion functions, and wide-
character functions.
LC_MESSAGES Affects the affirmative and negative response expressions
returned by nl_langinfo() and the way message catalogs are
located. It may also affect the behavior of functions that
return or write message strings.
LC_MONETARY Affects the behavior of functions that handle monetary val‐
ues.
LC_NUMERIC Affects the behavior of functions that handle numeric val‐
ues.
LC_TIME Affects the behavior of the time conversion functions.
The locale argument is a pointer to a character string containing the
required setting of category. The contents of this string are imple‐
mentation-defined. In addition, the following preset values of locale
are defined for all settings of category:
"POSIX" Specifies the minimal environment for C-language transla‐
tion called the POSIX locale. The POSIX locale is the
default global locale at entry to main().
"C" Equivalent to "POSIX".
"" Specifies an implementation-defined native environment.
The determination of the name of the new locale for the
specified category depends on the value of the associated
environment variables, LC_* and LANG; see the Base Defini‐
tions volume of POSIX.1‐2008, Chapter 7, Locale and Chapter
8, Environment Variables.
A null pointer
Directs setlocale() to query the current global locale set‐
ting and return the name of the locale if category is not
LC_ALL, or a string which encodes the locale name(s) for
all of the individual categories if category is LC_ALL.
Setting all of the categories of the global locale is similar to suc‐
cessively setting each individual category of the global locale, except
that all error checking is done before any actions are performed. To
set all the categories of the global locale, setlocale() can be invoked
as:
setlocale(LC_ALL, "");
In this case, setlocale() shall first verify that the values of all the
environment variables it needs according to the precedence rules
(described in the Base Definitions volume of POSIX.1‐2008, Chapter 8,
Environment Variables) indicate supported locales. If the value of any
of these environment variable searches yields a locale that is not sup‐
ported (and non-null), setlocale() shall return a null pointer and the
global locale shall not be changed. If all environment variables name
supported locales, setlocale() shall proceed as if it had been called
for each category, using the appropriate value from the associated
environment variable or from the implementation-defined default if
there is no such value.
The global locale established using setlocale() shall only be used in
threads for which no current locale has been set using uselocale() or
whose current locale has been set to the global locale using uselo‐
cale(LC_GLOBAL_LOCALE).
The implementation shall behave as if no function defined in this vol‐
ume of POSIX.1‐2008 calls setlocale().
RETURN VALUE
Upon successful completion, setlocale() shall return the string associ‐
ated with the specified category for the new locale. Otherwise, setlo‐
cale() shall return a null pointer and the global locale shall not be
changed.
A null pointer for locale shall cause setlocale() to return a pointer
to the string associated with the specified category for the current
global locale. The global locale shall not be changed.
The string returned by setlocale() is such that a subsequent call with
that string and its associated category shall restore that part of the
global locale. The application shall not modify the string returned.
The returned string pointer might be invalidated or the string content
might be overwritten by a subsequent call to setlocale().
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
The following code illustrates how a program can initialize the inter‐
national environment for one language, while selectively modifying the
global locale such that regular expressions and string operations can
be applied to text recorded in a different language:
setlocale(LC_ALL, "De");
setlocale(LC_COLLATE, "Fr@dict");
Internationalized programs can initiate language operation according to
environment variable settings (see the Base Definitions volume of
POSIX.1‐2008, Section 8.2, Internationalization Variables) by calling
setlocale() as follows:
setlocale(LC_ALL, "");
Changing the setting of LC_MESSAGES has no effect on catalogs that have
already been opened by calls to catopen().
In order to make use of different locale settings while multiple
threads are running, applications should use uselocale() in preference
to setlocale().
RATIONALE
References to the international environment or locale in the following
text relate to the global locale for the process. This can be overrid‐
den for individual threads using uselocale().
The ISO C standard defines a collection of functions to support inter‐
nationalization. One of the most significant aspects of these func‐
tions is a facility to set and query the international environment.
The international environment is a repository of information that
affects the behavior of certain functionality, namely:
1. Character handling
2. Collating
3. Date/time formatting
4. Numeric editing
5. Monetary formatting
6. Messaging
The setlocale() function provides the application developer with the
ability to set all or portions, called categories, of the international
environment. These categories correspond to the areas of functionality
mentioned above. The syntax for setlocale() is as follows:
char *setlocale(int category, const char *locale);
where category is the name of one of following categories, namely:
LC_COLLATE LC_CTYPE LC_MESSAGES LC_MONETARY LC_NUMERIC LC_TIME
In addition, a special value called LC_ALL directs setlocale() to set
all categories.
There are two primary uses of setlocale():
1. Querying the international environment to find out what it is set
to
2. Setting the international environment, or locale, to a specific
value
The behavior of setlocale() in these two areas is described below.
Since it is difficult to describe the behavior in words, examples are
used to illustrate the behavior of specific uses.
To query the international environment, setlocale() is invoked with a
specific category and the null pointer as the locale. The null pointer
is a special directive to setlocale() that tells it to query rather
than set the international environment. The following syntax is used
to query the name of the international environment:
setlocale({LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES, LC_MONETARY, \
LC_NUMERIC, LC_TIME},(char *) NULL);
The setlocale() function shall return the string corresponding to the
current international environment. This value may be used by a subse‐
quent call to setlocale() to reset the international environment to
this value. However, it should be noted that the return value from set‐
locale() may be a pointer to a static area within the function and is
not guaranteed to remain unchanged (that is, it may be modified by a
subsequent call to setlocale()). Therefore, if the purpose of calling
setlocale() is to save the value of the current international environ‐
ment so it can be changed and reset later, the return value should be
copied to an array of char in the calling program.
There are three ways to set the international environment with setlo‐
cale():
setlocale(category, string)
This usage sets a specific category in the international environ‐
ment to a specific value corresponding to the value of the
string. A specific example is provided below:
setlocale(LC_ALL, "fr_FR.ISO-8859-1");
In this example, all categories of the international environment
are set to the locale corresponding to the string
"fr_FR.ISO-8859-1", or to the French language as spoken in France
using the ISO/IEC 8859‐1:1998 standard codeset.
If the string does not correspond to a valid locale, setlocale()
shall return a null pointer and the international environment is
not changed. Otherwise, setlocale() shall return the name of the
locale just set.
setlocale(category, "C")
The ISO C standard states that one locale must exist on all con‐
forming implementations. The name of the locale is C and corre‐
sponds to a minimal international environment needed to support
the C programming language.
setlocale(category, "")
This sets a specific category to an implementation-defined
default. This corresponds to the value of the environment vari‐
ables.
FUTURE DIRECTIONS
None.
SEE ALSOcatopen(), exec, fprintf(), fscanf(), isalnum(), isalpha(), isblank(),
iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), iss‐
pace(), isupper(), iswalnum(), iswalpha(), iswblank(), iswcntrl(),
iswctype(), iswdigit(), iswgraph(), iswlower(), iswprint(), iswpunct(),
iswspace(), iswupper(), iswxdigit(), isxdigit(), localeconv(), mblen(),
mbstowcs(), mbtowc(), nl_langinfo(), perror(), psiginfo(), setlocale(),
strcoll(), strerror(), strfmon(), strsignal(), strtod(), strxfrm(),
tolower(), toupper(), towlower(), towupper(), uselocale(), wcscoll(),
wcstod(), wcstombs(), wcsxfrm(), wctomb()
The Base Definitions volume of POSIX.1‐2008, Chapter 7, Locale, Chapter
8, Environment Variables, <langinfo.h>, <locale.h>
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 Electri‐
cal 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 in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 SETLOCALE(3P)
