This function performs a catalog lookup to resolve the URI specified by uri, returning the system path name for the resource. If the identifier is not found in any of the catalog files in the search path, the uri_resolve function returns a null string.

catalogpath specifies a list of directories to search for the catalog file. If it is not specified, the path list specified in the set catalogpath option, which is initialized from the environment variable APTCATPATH, is searched.

The uri_resolve(uri, catpath) function is equivalent to catalog_resolve("URI", uri, "", "", catpath).