The category argument allows a specific category of the locale settings to be used for fetching a message.  Valid categories are:
LC_CTYPE, LC_NUMERIC, LC_TIME, LC_COLLATE, LC_MONETARY, LC_MESSAGES and LC_ALL.
Note that the category must be specified with a numeric value, instead of the constant name.  The values are:
LC_CTYPE        0
LC_NUMERIC      1
LC_TIME         2
LC_COLLATE      3
LC_MONETARY     4
LC_MESSAGES     5
LC_ALL          6