NAME
setlocale - set program locale
SYNOPSIS
#include <locale.h>
char *setlocale(int category, const char *locale);
DESCRIPTION
The setlocale() function selects the appropriate piece of the program’s
locale, as specified by the category and locale arguments, and may be
used to change or query the program’s entire locale or portions
thereof. The value LC_ALL for category names the program’s entire
locale; other values for category name only a part of the program’s
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 what strings are expected by commands and utilities as
affirmative or negative responses.
It also affects what strings are given by commands and utilities as
affirmative or negative responses, and the content of messages.
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. If setlocale() is not invoked, the
POSIX locale is the default at entry to main().
"C" Equivalent to "POSIX" .
"" Specifies an implementation-defined native environment. This
corresponds to the value of the associated environment
variables, LC_* and LANG ; see the Base Definitions volume of
IEEE Std 1003.1-2001, Chapter 7, Locale and the Base Definitions
volume of IEEE Std 1003.1-2001, Chapter 8, Environment
Variables.
A null pointer
Used to direct setlocale() to query the current
internationalized environment and return the name of the locale.
The locale state is common to all threads within a process.
RETURN VALUE
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 program’s locale is not
changed.
A null pointer for locale causes setlocale() to return a pointer to the
string associated with the category for the program’s current locale.
The program’s 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
program’s locale. The application shall not modify the string returned
which may 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
international environment for one language, while selectively modifying
the program’s 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 must call setlocale() to initiate a specific
language operation. This can be done 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().
RATIONALE
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.
FUTURE DIRECTIONS
None.
SEE ALSO
exec() , isalnum() , isalpha() , isblank() , iscntrl() , isdigit() ,
isgraph() , islower() , isprint() , ispunct() , isspace() , isupper() ,
iswalnum() , iswalpha() , iswblank() , iswcntrl() , iswctype() ,
iswdigit() , iswgraph() , iswlower() , iswprint() , iswpunct() ,
iswspace() , iswupper() , iswxdigit() , isxdigit() , localeconv() ,
mblen() , mbstowcs() , mbtowc() , nl_langinfo() , printf() , scanf() ,
setlocale , strcoll() , strerror() , strfmon() , strtod() , strxfrm() ,
tolower() , toupper() , towlower() , towupper() , wcscoll() , wcstod()
, wcstombs() , wcsxfrm() , wctomb() , the Base Definitions volume of
IEEE Std 1003.1-2001, <langinfo.h>, <locale.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .