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,  execut-
          ing   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.  If the copy file is specified with
          this flag, instead of using  the  scancontext  copyfile
          command,  the  file is disassociated from the scan con-
          text at the end of the scan.

          This command does not work on files  containing  binary
          data (bytes of zero).

          This command is provided by Extended Tcl.