       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 std
              out, stderr and any other open output  file  before
              doing  the fork. Otherwise characters from the par
              ent 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.
