SETLOCALE(3) Linux Programmer’s Manual SETLOCALE(3)
setlocale - set the current locale.
#include <locale.h>
char *setlocale(int category, const char * locale);
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 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.
LC_COLLATE
for regular expression matching (it determines the meaning of
range expressions and equivalence classes) and string collation.
LC_CTYPE
for regular expression matching, character classification, con‐
version, case-sensitive comparison, and wide character func‐
tions.
LC_MESSAGES
for localizable natural-language messages.
LC_MONETARY
for monetary formatting.
LC_NUMERIC
for number formatting (such as the decimal point and the thou‐
sands separator).
LC_TIME
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_MONE‐
TARY, 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 cor‐
responds to the 7-bit ASCII character set.
A locale name is typically of the form language[_territory][.code‐
set][@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 set‐
locale(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 process‐
ing if MB_CUR_MAX > 1, and by using strcoll(), wstrcoll() or strxfrm(),
wstrxfrm() to compare strings.
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.
ANSI C, POSIX.1
Linux (that is, GNU libc) supports the portable locales "C" and
"POSIX". In the good old days there used to be support for the Euro‐
pean 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.
locale(1), localedef(1), strcoll(3), isalpha(3), localeconv(3), strf‐
time(3), charsets(4), locale(7)
GNU July 4, 1999 SETLOCALE(3)