SETLOCALE(3)

NAME
setlocale - set the current locale.

SYNOPSIS
#include <locale.h>

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

DESCRIPTION
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.

LC_ALL
    for all of the locale.

LC_COLLATE
    for string collation. Affected functions: strcoll(), strxfrm(), wstrcoll(), wstrxfrm().

LC_CTYPE
    for character classification, conversion, case-sensitive comparison, and regular expression matching. Affected functions: isalnum(), isalpha(), isblank(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), isxdigit(), tolower(), toupper(), strcasecmp(), strncasecmp(), iswalnum(), iswalpha(), iswblank(), iswcntrl(), iswdigit(), iswgraph(), iswlower(), iswprint(), iswpunct(), iswspace(), iswupper(), iswxdigit(), iswctype(), towlower(), towupper(), towctrans(), wcscasecmp(), wcsncasecmp(), wcwidth(), wcswidth(), regcomp, regexec().

LC_MESSAGES
    for localizable natural-language messages. Affected functions: gettext(), dgettext().

LC_MONETARY
    for monetary formatting. Affected: the function localeconv().

LC_NUMERIC
    for number formatting (such as the decimal point and the thousands separator). Affected: the function localeconv().

LC_TIME
    for time and date formatting. Affected: the function strftime().

If locale is "", each part of the locale that should be modified is set according to the environment variables. The following environment variables are inspected, in order of precedence. If an environment variable is not set or if its value is empty, it is ignored.

LC_COLLATE
    "LC_ALL", "LC_COLLATE", "LANG".

LC_CTYPE
    "LC_ALL", "LC_CTYPE", "LANG".

LC_MESSAGES
    "LANGUAGE" (may contain several, colon-separated, locale names), "LC_ALL", "LC_MESSAGES", "LANG".

LC_MONETARY
    "LC_ALL", "LC_MONETARY", "LANG".

LC_NUMERIC
    "LC_ALL", "LC_NUMERIC", "LANG".

LC_TIME
    "LC_ALL", "LC_TIME", "LANG".

The locale "C" or "POSIX" is a portable locale; its LC_CTYPE part corresponds to the 7-bit ASCII character set.

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.

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

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, by using the values returned from a localeconv() call for locale - dependent information, by using the multi-byte and wide character functions for text processing if MB_CUR_MAX > 1, and by using strcoll(), wstrcoll() or strxfrm(), wstrxfrm() to compare strings.

RETURN VALUE
A successful call to setlocale() returns a 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.

CONFORMING TO
ANSI C, POSIX.1

NOTES
Linux (that is, GNU libc) supports the portable locales "C" and "POSIX". In the good old days there used to be support for the European Latin-1 "ISO-8859-1" locale (e.g. in libc-4.5.21 and libc-4.6.27), and the Russian "KOI-8" (more precisely, "koi-8r") locale (e.g. in libc-4.6.27), so that having an environment variable LC_CTYPE=ISO-8859-1 sufficed to make isprint() return the right answer. These days non-English speaking Europeans have to work a bit harder, and must install actual locale files.

The printf() and scanf() families of functions are affected by the current locale: The decimal dot depends on the LC_NUMERIC part of the locale, and the tokenization uses isspace() and thus depends on the LC_CTYPE part of the locale.

SEE ALSO
locale(1), localedef(1), strcoll(3), isalpha(3), localeconv(3), strftime(3), charsets(4), locale(7)