Searches a string for a file specification and parses the
    components of that file specification.

    Format

      SYS$FILESCAN  srcstr ,valuelst ,[fldflags] ,[auxout] ,[retlen]

    C Prototype

      int sys$filescan  (void *srcstr, void *valuelst, unsigned int

                        *fldflags, void *auxout, unsigned short int

                        *retlen);