Understanding locale environment variables

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Multicultural support 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 environment variable 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 Manage Language Environment menu in SMIT. 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 the /etc/environment file.
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.

Application developers who write applications that do not display multibyte characters on a terminal should make sure the LC_MESSAGES value is not set to C@lft. If necessary, disable the setting with the putenv("LC_MESSAGES=") subroutine. The result is output that uses translated message catalogs. C@lft is disabled by login sessions that can display multibyte characters. Processes launched using cron or inittab retain the C@lft LC_MESSAGES value and use the setlocale() subroutine to establish the language environment for default messages.

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 multicultural support 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: high, medium, and low. Environment variables in the high priority class are:
  • LC_ALL
  • LC_COLLATE
  • LC_CTYPE
Environment variables in the medium priority class are:
  • LC_MESSAGES
  • LC_MONETARY
  • LC_NUMERIC
  • LC_TIME
The environment variable in the low priority class is:
  • LANG
When a locale is requested by the setlocale subroutine for a particular category or for all categories, the environment variable settings are queried by their priority level in the following manner:
  • If the LC_ALL environment variable is set, all six categories use the locale it specified. For example, if the LC_ALL environment variable is equal to en_US and the LANG environment variable is equal to fr_FR, a call to the setlocale subroutine sets each of the six categories to the en_US locale.
  • If the LC_ALL environment variable is not set, each individual category uses the locale specified by its corresponding environment variable. For example, if the LC_ALL environment variable is not set, the LC_COLLATE environment variable is set to de_DE, and the LC_TIME environment variable is set to fr_CA, then a call to the setlocale subroutine sets the LC_COLLATE category to de_DE and the LC_TIME category to fr_CA. Neither environment variable has precedence over the other in this situation.
  • If the LC_ALL environment variable is not set, and a value for a particular LC_* environment variable is not set, the value of the LANG environment variable determines the setting for that specific category. For example, if the LC_ALL environment variable is not set, the LC_CTYPE environment variable is set to en_US, the LC_NUMERIC environment variable is not set, and the LANG environment variable is set to is_IS, then a call to the setlocale subroutine sets the LC_CTYPE category to en_US and the LC_NUMERIC category to is_IS. The LANG environment variable specifies the locale for only those categories not previously determined by an LC_* environment variable.
  • If the LC_ALL environment variable is not set, a value for a particular LC_* environment variable is not set, and the value of the LANG environment variable is not set, the locale for that specific category defaults to the C locale. For example, if the LC_ALL environment variable is not set, the LC_MONETARY environment variable is set to sv_SE, the LC_TIME environment variable is not set, and the LANG environment variable is not set, then a call to the setlocale subroutine sets the LC_MONETARY category to sv_SE and the LC_TIME category to C.