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. 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.