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SETLOCALE(3P) POSIX Programmer's Manual SETLOCALE(3P)
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.
setlocale — set program locale
#include <locale.h>
char *setlocale(int category, const char *locale);
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
collation 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
values.
LC_NUMERIC Affects the behavior of functions that handle numeric
values.
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
implementation-defined. In addition, the following preset values of
locale are defined for all settings of category:
"POSIX" Specifies the minimal environment for C-language
translation 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
Definitions volume of POSIX.1‐2008, Chapter 7, Locale and
Chapter 8, Environment Variables.
A null pointer
Directs setlocale() to query the current global locale
setting 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
successively 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 supported (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
uselocale(LC_GLOBAL_LOCALE).
The implementation shall behave as if no function defined in this
volume of POSIX.1‐2008 calls setlocale().
Upon successful completion, setlocale() shall return the string
associated with the specified category for the new locale. Otherwise,
setlocale() 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().
No errors are defined.
The following sections are informative.
None.
The following code illustrates how a program can initialize the
international 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().
References to the international environment or locale in the
following text relate to the global locale for the process. This can
be overridden for individual threads using uselocale().
The ISO C standard defines a collection of functions to support
internationalization. One of the most significant aspects of these
functions 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
subsequent call to setlocale() to reset the international environment
to this value. However, it should be noted that the return value from
setlocale() 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
environment 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
setlocale():
setlocale(category, string)
This usage sets a specific category in the international
environment 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
conforming implementations. The name of the locale is C and
corresponds 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
variables.
None.
catopen(3p), exec(1p), fprintf(3p), fscanf(3p), isalnum(3p),
isalpha(3p), isblank(3p), iscntrl(3p), isdigit(3p), isgraph(3p),
islower(3p), isprint(3p), ispunct(3p), isspace(3p), isupper(3p),
iswalnum(3p), iswalpha(3p), iswblank(3p), iswcntrl(3p), iswctype(3p),
iswdigit(3p), iswgraph(3p), iswlower(3p), iswprint(3p), iswpunct(3p),
iswspace(3p), iswupper(3p), iswxdigit(3p), isxdigit(3p),
localeconv(3p), mblen(3p), mbstowcs(3p), mbtowc(3p), nl_langinfo(3p),
perror(3p), psiginfo(3p), setlocale(3p), strcoll(3p), strerror(3p),
strfmon(3p), strsignal(3p), strtod(3p), strxfrm(3p), tolower(3p),
toupper(3p), towlower(3p), towupper(3p), uselocale(3p), wcscoll(3p),
wcstod(3p), wcstombs(3p), wcsxfrm(3p), wctomb(3p)
The Base Definitions volume of POSIX.1‐2008, Chapter 7, Locale,
Chapter 8, Environment Variables, langinfo.h(0p), locale.h(0p)
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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 SETLOCALE(3P)
Pages that refer to this page: ctype.h(0p), locale.h(0p), wctype.h(0p), awk(1p), exec(3p), fprintf(3p), fscanf(3p), fwprintf(3p), fwscanf(3p), getdate(3p), isalnum(3p), isalpha(3p), isblank(3p), iscntrl(3p), isgraph(3p), islower(3p), isprint(3p), ispunct(3p), isspace(3p), isupper(3p), iswalnum(3p), iswalpha(3p), iswblank(3p), iswcntrl(3p), iswctype(3p), iswdigit(3p), iswgraph(3p), iswlower(3p), iswprint(3p), iswpunct(3p), iswspace(3p), iswupper(3p), iswxdigit(3p), localeconv(3p), nl_langinfo(3p), setlocale(3p), strsignal(3p), strtod(3p), tolower(3p), toupper(3p), towlower(3p), towupper(3p), uselocale(3p), wcstod(3p)