       scanfile ?-copyfile copyFileId? contexthandle fileId
              Scan  the  file  specified by fileId, starting from
              the current file position.  Check all  patterns  in
              the scan context specified by contexthandle against
              it, executing the match commands  corresponding  to
              patterns matched.

              If  the  optional  -copyfile argument is specified,
              the next argument is a file ID to which  all  lines
              not  matched  by any pattern (excluding the default
              pattern) are to be written.

              This command is provided by Extended Tcl.
