LOCALE (7)
Description of multi-language support
SYNOPSIS
#include <locale.h>
DESCRIPTION
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 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 formatting.
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:
LC_COLLATE
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".
LC_CTYPE
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() .
LC_MONETARY
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() .
LC_MESSAGES
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.
LC_NUMERIC
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.
LC_TIME
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
If the second argument to
setlocale()
is empty string,
for the default locale, it is determined using the following steps:
If there is a non-null environment variable
LC_ALL ,
the value of
LC_ALL
is used.
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.
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:
struct lconv
{
/* 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. */
char *grouping;
/* Monetary information. */
/* First three chars are a currency symbol from ISO 4217.
Fourth char is the separator. Fifth char is '\0'. */
char *int_curr_symbol;
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. */
char p_cs_precedes;
/* 1 if a space separates currency_symbol from a positive value. */
char p_sep_by_space;
/* 1 if currency_symbol precedes a negative value, 0 if succeeds. */
char n_cs_precedes;
/* 1 if a space separates currency_symbol from a negative value. */
char n_sep_by_space;
/* 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. */
char p_sign_posn;
char n_sign_posn;
};
CONFORMS TO
SEE ALSO
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