       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.
