LOCALE(7) Linux Programmer's Manual LOCALE(7)
locale - Description of multi-language support
A locale is a set of language and cultural rules. These
cover aspects such as language for messages, different
character sets, lexigraphic conventions, etc. A program
needs to be able to determine its locale and act accord-
ingly to be portable to different cultures.
The header <locale.h> declares data types, functions and
macros which are useful in this task.
The functions it declares are setlocale() to set the cur-
rent locale, and localeconv() to get information about
There are different categories for local information a
program might need; they are declared as macros. Using
them as the first argument to the setlocale() function, it
is possible to set one of these to the desired locale:
This is used to change the behaviour of the func-
tions strcoll() and strxfrm(), which are used to
compare strings in the local alphabet. For exam-
ple, the German sharp s is sorted as "ss".
This changes the behaviour of the character han-
dling and classification functions, such as isup-
per() and toupper(), and the multi-byte character
functions such as mblen() or wctomb().
changes the information returned by localeconv()
which describes the way numbers are usually
printed, with details such as decimal point versus
decimal comma. This information is internally used
by the functions strfmon() .
changes the language messages are displayed in and
how an affirmative or negative answer looks like.
The GNU C-library contains the rpmatch() function
to ease the use of these information.
changes the informations used by the printf() and
scanf() family of functions, when they are advised
to use the locale-settings. This information can
also be read with the localeconv() function.
changes the behaviour of the strftime() function to
display the current time in a locally acceptable
form; for example, most of Europe uses a 24-hour
clock vs. the US' 12-hour clock.
LC_ALL All of the above.
If the second argument to setlocale() is empty string, "",
for the default locale, it is determined using the follow-
1. If there is a non-null environment variable LC_ALL,
the value of LC_ALL is used.
2. If an environment variable with the same name as
one of the categories above exists and is non-null,
its value is used for that category.
3. If there is a non-null environment variable LANG,
the value of LANG is used.
Values about local numeric formatting is made available in
a struct lconv returned by the localeconv() function,
which has the following declaration:
/* Numeric (non-monetary) information. */
char *decimal_point; /* Decimal point character. */
char *thousands_sep; /* Thousands separator. */
/* Each element is the number of digits in each group;
elements with higher indices are farther left.
An element with value CHAR_MAX means that no further grouping is done.
An element with value 0 means that the previous element is used
for all groups farther left. */
/* Monetary information. */
/* First three chars are a currency symbol from ISO 4217.
Fourth char is the separator. Fifth char is ' '. */
char *currency_symbol; /* Local currency symbol. */
char *mon_decimal_point; /* Decimal point character. */
char *mon_thousands_sep; /* Thousands separator. */
char *mon_grouping; /* Like `grouping' element (above). */
char *positive_sign; /* Sign for positive values. */
char *negative_sign; /* Sign for negative values. */
char int_frac_digits; /* Int'l fractional digits. */
char frac_digits; /* Local fractional digits. */
/* 1 if currency_symbol precedes a positive value, 0 if succeeds. */
/* 1 if a space separates currency_symbol from a positive value. */
/* 1 if currency_symbol precedes a negative value, 0 if succeeds. */
/* 1 if a space separates currency_symbol from a negative value. */
/* Positive and negative sign positions:
0 Parentheses surround the quantity and currency_symbol.
1 The sign string precedes the quantity and currency_symbol.
2 The sign string succeeds the quantity and currency_symbol.
3 The sign string immediately precedes the currency_symbol.
4 The sign string immediately succeeds the currency_symbol. */
setlocale(3), localeconv(3), locale(1), localedef(1) ,
rpmatch(3), strfmon(3), strcoll(3), strxfrm(3), strf-
Linux April 24, 1993 1