trusty (3) setlocale.3posix.gz
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 .