System Management Concepts: Operating System and Devices

Understanding Locale Environment Variables

National Language Support (NLS) uses several environment variables to influence the selection of locales. You can set the values of these variables to change search paths for locale information:

LANG	Specifies the installation default locale. Note: The LANG value is established at installation. (This is the locale every process uses unless the LC_* environment variables are set). The LANG environment variable can be changed by using the System Management Interface Tool (SMIT) Overview. The C and POSIX locales are designed to offer the best performance.
LC_ALL	Overrides the value of the LANG environment variable and the values of any other LC_* environment variables.
LC_COLLATE	Specifies the locale to use for LC_COLLATE category information. The LC_COLLATE category determines character-collation or string-collation rules governing the behavior of ranges, equivalence classes, and multicharacter collating elements.
LC_CTYPE	Specifies the locale to use for LC_CTYPE category information. The LC_CTYPE category determines character handling rules governing the interpretation of sequences of bytes of text data characters (that is, single-byte versus multibyte characters), the classification of characters (for example, alpha, digit, and so on), and the behavior of character classes.
LC__FASTMSG	Specifies that default messages are used for the C and POSIX locales and that NLSPATH are ignored when LC__FASTMSG is set to `true`; otherwise, POSIX compliant message handling will be performed. The default value will be `LC__FASTMSG=true` in /etc/environment.
LC_MESSAGES	Specifies the locale to use for LC_MESSAGES category information. The LC_MESSAGES category determines rules governing affirmative and negative responses and the locale (language) for messages and menus.
LC_MONETARY	Specifies the locale to use for LC_MONETARY category information. The LC_MONETARY category determines the rules governing monetary-related formatting.
LC_NUMERIC	Specifies the locale to use for LC_NUMERIC category information. The LC_NUMERIC category determines the rules governing nonmonetary numeric formatting.
LC_TIME	Specifies the locale to use for LC_TIME category information. The LC_TIME category determines the rules governing date and time formatting.
LOCPATH	Specifies the search path for localized information, including binary locale files, input methods, and code-set converters. Note: All setuid and setgid programs ignore the LOCPATH environment variable.
NLSPATH	Specifies the search path for locating message catalog files. This environment variable is used by the Message Facility component of the NLS subsystem. See the catopen subroutine for more information about expected format of the NLSPATH variable.

The environment variables that affect locale selection can be grouped into three priority classes:

Locale Environment Variable Hierarchy
Priority Class	Environment Variables
High	LC_ALL
	LC_COLLATE
	LC_CTYPE
Medium	LC_MESSAGES
	LC_MONETARY
	LC_NUMERIC
	LC_TIME
Low	LANG

The behavior of an internationalized program is affected by the locale environment variables in the following manner:

If the LC_ALL environment variable is set, the value of the LC_ALL variable is used for all categories. For example, if the LC_ALL environment variable is equal to en_US and the LANG environment variable is equal to fr_FR, the locale is set to en_US.
If the LC_ALL environment variable is not set, the values specified for medium-priority environment variables are used. For example, if the LANG environment variable is set to en_US and the LC_TIME environment variable is set to fr_FR, then the LC_TIME category is loaded from the fr_FR locale database. The LC_TIME environment variable does not affect the behavior of any other category.
If individual LC_* environment variables are not set, the value of the LANG environment variable specifies the locale for all remaining categories.
If the LANG variable is not set, the locale for all remaining categories defaults to the C locale.