locale — Description of multilanguage support
#include <locale.h>
A locale is a set of language and cultural rules. These cover aspects such as language for messages, different character sets, lexicographic 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(3) to set the current locale, and localeconv(3) 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(3) function, it is possible to set one of these to the desired locale:
LC_COLLATEThis is used to change the behavior of the functions strcoll(3) and strxfrm(3), which are used to compare strings in the local alphabet. For example, the German sharp s is sorted as "ss".
LC_CTYPEThis changes the behavior of the character handling and classification functions, such as isupper(3) and toupper(3), and the multibyte character functions such as mblen(3) or wctomb(3).
LC_MONETARYchanges the information returned by localeconv(3) which describes the way numbers are usually printed, with details such as decimal point versus decimal comma. This information is internally used by the function strfmon(3).
LC_MESSAGESchanges the language messages are displayed in and
what an affirmative or negative answer looks like. The
GNU C-library contains the gettext(3), ngettext(3), and
rpmatch(3) functions
to ease the use of these information. The GNU gettext
family of functions also obey the environment variable
LANGUAGE (containing a
colon-separated list of locales) if the category is set
to a valid locale other than "C".
LC_NUMERICchanges the information used by the printf(3) and scanf(3) family of functions, when they are advised to use the locale-settings. This information can also be read with the localeconv(3) function.
LC_TIMEchanges the behavior of the strftime(3) function to display the current time in a locally acceptable form; for example, most of Europe uses a 24-hour clock versus the 12-hour clock used in the United States.
LC_ALLAll of the above.
If the second argument to setlocale(3) 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(3) function, which has the following declaration:
struct lconv { char * decimal_point;char * thousands_sep;
of radix character */char * grouping;
group; elements with higher indices are
further 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 further left. */char * int_curr_symbol;
from ISO 4217. Fourth char is the
separator. Fifth char is \(aq\\0\(aq. */char * currency_symbol;char * mon_decimal_point;char * mon_thousands_sep;char * mon_grouping;char * positive_sign;char * negative_sign;char int_frac_digits;char frac_digits;char p_cs_precedes;
positive value, 0 if succeeds */char p_sep_by_space;
from a positive value */char n_cs_precedes;
negative value, 0 if succeeds */char n_sep_by_space;
from a negative value */
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;};
locale(1), localedef(1), gettext(3), localeconv(3), ngettext(3), nl_langinfo(3), rpmatch(3), setlocale(3), strcoll(3), strfmon(3), strftime(3), strxfrm(3)