Opens the message catalog catname. This may be a
relative pathname, in which case the NLSPATH
environment variable is searched to find an absolute path
to the message catalog. A handle in the form
msgcatN is returned. Normally, errors
are ignored, and in the case of a failed call to
catopen, a handle is returned to an unopened
message catalog. (This handle may still be passed to
catgets and catclose, causing
catgets to simply return the default string, as
described above. If the -fail option is
specified, an error is returned if the open fails. The
option -nofail specifies the default behavior of
not returning an error when catopen fails to open
a specified message catalog. If the handle from a failed
catopen is passed to catgets, the
default string is returned.