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 char-
acter sets, lexigraphic conventions, etc. A program needs
to be able to determine its locale and act accordingly 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 current
locale, and localeconv() to get information about number
There are different categories for local information a pro-
gram might need; they are declared as macros. Using them as
the first argument to the setlocale() function, it is possi-
ble to set one of these to the desired locale:
This is used to change the behaviour of the functions
strcoll() and strxfrm(), which are used to compare
strings in the local alphabet. For example, the German
sharp s is sorted as "ss".
This changes the behaviour of the character handling
and classification functions, such as isupper() 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
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.
All of the above.
If the second argument to setlocale() is empty string, for
the default locale, it is determined using the following
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), rpmatch(3),
strfmon(3), strcoll(3), strftime(3)