setlocale - set the current locale
char *setlocale(int category, const char *locale);
The setlocale() function is used to set or query the program's current
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.
for regular expression matching (it determines the meaning of
range expressions and equivalence classes) and string collation.
for regular expression matching, character classification,
conversion, case-sensitive comparison, and wide character
for localizable natural-language messages.
for monetary formatting.
for number formatting (such as the decimal point and the
for time and date formatting.
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 "", 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 (LC_COLLATE, LC_CTYPE,
LC_MESSAGES, LC_MONETARY, LC_NUMERIC, LC_TIME) 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; 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. For a
list of all supported locales, try "locale -a", cf. locale(1).
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:
after program initialization, by using the values returned from a
localeconv(3) call for locale-dependent information, by using the
multibyte and wide character functions for text processing if
MB_CUR_MAX > 1, and by using strcoll(3), wcscoll(3) or strxfrm(3),
wcsxfrm(3) to compare strings.
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
C89, C99, POSIX.1-2001.
Linux (that is, glibc) 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(3) return the right
answer. These days non-English speaking Europeans have to work a bit
harder, and must install actual locale files.
locale(1), localedef(1), isalpha(3), localeconv(3), nl_langinfo(3),
rpmatch(3), strcoll(3), strftime(3), charsets(7), locale(7)
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