This function does a catalog lookup to resolve the entity specified by the name, pubid and sysid parameters, returning the system path name. If the identifier is not found in any of the catalog files in the search path, the entity_resolve function returns a null string.

The name argument specifies the entity name to be used in the catalog lookup. If can be a null string if the pubid and/or sysid are non-null. The name must not start with the & general delimiter.

The pubid argument specifies an optional public identifier associated with the entity declaration.

The sysid argument specifies an optional system identifier associated with the entity declaration.

The catalogpath argument 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 function public_id_path(pubid, "", catpath) is equivalent to entity_resolve("", pubid, "", catpath).

The function entity_resolve(name, pubid, sysid, catpath) is equivalent to catalog_resolve("ENTITY", name, pubid, sysid, catpath).