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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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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.1‐2017 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.1‐2017,
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.1‐2017,
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.1‐2017 calls setlocale().
The setlocale() function need not be thread-safe.
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(). The returned pointer might also be invalidated if
the calling thread is terminated.
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.1‐2017, 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), newlocale(3p), nl_langinfo(3p),
perror(3p), psiginfo(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.1‐2017, 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 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. 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.opengroup.org/unix/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 2017 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), strsignal(3p), strtod(3p), tolower(3p), toupper(3p), towlower(3p), towupper(3p), uselocale(3p), wcstod(3p)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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