setlocale(3p) — Linux manual page


SETLOCALE(3P)             POSIX Programmer's Manual            SETLOCALE(3P)

PROLOG         top

       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.

NAME         top

       setlocale — set program locale

SYNOPSIS         top

       #include <locale.h>

       char *setlocale(int category, const char *locale);

DESCRIPTION         top

       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

       LC_NUMERIC  Affects the behavior of functions that handle numeric

       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

       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

       The implementation shall behave as if no function defined in this
       volume of POSIX.1‐2008 calls setlocale().

RETURN VALUE         top

       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

ERRORS         top

       No errors are defined.

       The following sections are informative.

EXAMPLES         top



       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().

RATIONALE         top

       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,

        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

           char *setlocale(int category, const char *locale);

       where category is the name of one of following categories, namely:


       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

        2. Setting the international environment, or locale, to a specific

       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:

               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(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



SEE ALSO         top

       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)

COPYRIGHT         top

       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 .

       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 .

IEEE/The Open Group                 2013                       SETLOCALE(3P)

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