catopen is a Tclx command for opening a message catalog.
catopen ?-fail | -nofail? catname
Open the message catalog catname. This may be a relative
path name, 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.See also catgets and catclose.