setlocale(3) — Linux manual page


SETLOCALE(3)            Linux Programmer's Manual           SETLOCALE(3)

NAME         top

       setlocale - set the current locale

SYNOPSIS         top

       #include <locale.h>

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

DESCRIPTION         top

       The setlocale() function is used to set or query the program's
       current locale.

       If locale is not NULL, the program's current locale is modified
       according to the arguments.  The argument category determines
       which parts of the program's current locale should be modified.

       Category            Governs
       LC_ALL              All of the locale
       LC_ADDRESS          Formatting of addresses and geography-related
                           items (*)
       LC_COLLATE          String collation
       LC_CTYPE            Character classification
       LC_IDENTIFICATION   Metadata describing the locale (*)
       LC_MEASUREMENT      Settings related to measurements (metric
                           versus US customary) (*)
       LC_MESSAGES         Localizable natural-language messages
       LC_MONETARY         Formatting of monetary values
       LC_NAME             Formatting of salutations for persons (*)
       LC_NUMERIC          Formatting of nonmonetary numeric values
       LC_PAPER            Settings related to the standard paper size
       LC_TELEPHONE        Formats to be used with telephone services
       LC_TIME             Formatting of date and time values

       The categories marked with an asterisk in the above table are GNU
       extensions.  For further information on these locale categories,
       see locale(7).

       The argument locale is a pointer to a character string containing
       the required setting of category.  Such a string is either a
       well-known constant like "C" or "da_DK" (see below), or an opaque
       string that was returned by another call of setlocale().

       If locale is an empty string, "", each part of the locale that
       should be modified is set according to the environment variables.
       The details are implementation-dependent.  For glibc, first
       (regardless of category), the environment variable LC_ALL is
       inspected, next the environment variable with the same name as
       the category (see the table above), and finally the environment
       variable LANG.  The first existing environment variable is used.
       If its value is not a valid locale specification, the locale is
       unchanged, and setlocale() returns NULL.

       The locale "C" or "POSIX" is a portable locale; it exists on all
       conforming systems.

       A locale name is typically of the form
       language[_territory][.codeset][@modifier], where language is an
       ISO 639 language code, territory is an ISO 3166 country code, and
       codeset is a character set or encoding identifier like ISO-8859-1
       or UTF-8.  For a list of all supported locales, try "locale -a"
       (see locale(1)).

       If locale is NULL, the current locale is only queried, not

       On startup of the main program, the portable "C" locale is
       selected as default.  A program may be made portable to all
       locales by calling:

           setlocale(LC_ALL, "");

       after program initialization, and then:

       • using the values returned from a localeconv(3) call for locale-
         dependent information;

       • using the multibyte and wide character functions for text
         processing if MB_CUR_MAX > 1;

       • using strcoll(3) and strxfrm(3) to compare strings; and

       • using wcscoll(3) and wcsxfrm(3) to compare wide-character

RETURN VALUE         top

       A successful call to setlocale() returns an opaque string that
       corresponds to the locale set.  This string may be allocated in
       static storage.  The string returned is such that a subsequent
       call with that string and its associated category will restore
       that part of the process's locale.  The return value is NULL if
       the request cannot be honored.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface          Attribute     Value                      │
       │setlocale()        │ Thread safety │ MT-Unsafe const:locale env │

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008, C89, C99.

       The C standards specify only the categories LC_ALL, LC_COLLATE,
       LC_MESSAGES.  The remaining categories are GNU extensions.

SEE ALSO         top

       locale(1), localedef(1), isalpha(3), localeconv(3),
       nl_langinfo(3), rpmatch(3), strcoll(3), strftime(3), charsets(7),

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at

GNU                            2021-03-22                   SETLOCALE(3)

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