In glibc, internationalization is done using locales. Locales are collection of conventions. Locales should be specified via environment variables. There are standard locales such as 'C' and 'POSIX' that are supported by all operating systems (OS).
The glibc features that should be internationalized are categorized. Each category can be specified separately with a locale as the user wishes. The environment variable corresponding to each category should be defined for the same. The list of such environment variables are as follows:
- LC_COLLATE
- LC_CTYPE
- LC_MONETRY
- LC_NUMERIC
- LC_TIME
- LC_MESSAGES
Also refer: Categories of Activities that Locales Affect
If the user prefers to specify a single locale for all categories, then the user can use the environment variable 'LC_ALL'.
Failing to define locale may end up with error on running the glibc test-suites via 'make check'.
Also read: problem in running glibc-2.2.5 testsuite