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Categories of Activities that Locales Affect
The purposes that locales serve are grouped into categories, so
that a user or a program can choose the locale for each category
independently. Here is a table of categories; each name is both an
environment variable that a user can set, and a macro name that you can
use as an argument to setlocale
.
LC_COLLATE
- This category applies to collation of strings (functions
strcoll
and strxfrm
); see Collation Functions.
LC_CTYPE
- This category applies to classification and conversion of characters,
and to multibyte and wide characters;
see Character Handling, and Character Set Handling.
LC_MONETARY
- This category applies to formatting monetary values; see General Numeric.
LC_NUMERIC
- This category applies to formatting numeric values that are not
monetary; see General Numeric.
LC_TIME
- This category applies to formatting date and time values; see
Formatting Calendar Time.
LC_MESSAGES
- This category applies to selecting the language used in the user
interface for message translation (see The Uniforum approach;
see Message catalogs a la X/Open).
LC_ALL
- This is not an environment variable; it is only a macro that you can use
with
setlocale
to set a single locale for all purposes. Setting
this environment variable overwrites all selections by the other
LC_*
variables or LANG
.
LANG
- If this environment variable is defined, its value specifies the locale
to use for all purposes except as overridden by the variables above.
When developing the message translation functions it was felt that the
functionality provided by the variables above is not sufficient. For
example, it should be possible to specify more than one locale name.
Take a Swedish user who better speaks German than English, and a program
whose messages are output in English by default. It should be possible
to specify that the first choice of language is Swedish, the second
German, and if this also fails to use English. This is
possible with the variable LANGUAGE
. For further description of
this GNU extension see Using gettextized software.