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 accord-
ing 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, con-
version, case-sensitive comparison, and wide character func-
for localizable natural-language messages.
for monetary formatting.
for number formatting (such as the decimal point and the thou-
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 implementa-
tion-dependent. For glibc, first (regardless of category), the envi-
ronment 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 set-
locale() returns NULL.
The locale "C" or "POSIX" is a portable locale; its LC_CTYPE part cor-
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 corre-
sponds to the locale set. This string may be allocated in static stor-
age. 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)
This page is part of release 3.35 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://man7.org/linux/man-pages/.
GNU 2008-12-05 SETLOCALE(3)
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