gencat[option]database msgfiles
Append (or merge) messages contained in one or more msgfiles
with the formatted message database file. If database doesn't exist,
it is created. Each message in msgfile is preceded by a numerical
identifier. Comment lines can be added by using a dollar sign at the
beginning of a line, followed by a space or tab.
Build a single database that is backward-compatible with databases
created by earlier versions of gencat.