       fork   Fork the current Tcl process.  Fork returns zero to
              the child process and the  process  number  of  the
              child  to the parent process.  If the fork fails, a
              Tcl error is generated.

              If an execl is not going to be performed before the
              child  process  does  output, or if a close and dup
              sequence is going to  be  performed  on  stdout  or
              stderr,  then  a  flush  should  be  issued against
              stdout, stderr  and  any  other  open  output  file
              before  doing  the  fork. Otherwise characters from
              the parent process pending in the buffers  will  be
              output by both the parent and child processes.

              Note:  If you are forking in a Tk based apllication
              you must execl before doing any  window  operations
              in  the child or you will receive a BadWindow error
              from the X server.

              The fork command is not available on Windows 95/NT.
