       1mfork   22mFork  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  1mexecl  22mis  not  going  to  be performed before the child
              process does output, or if a 1mclose 22mand 1mdup 22msequence is going  to
              be  performed on 1mstdout 22mor 1mstderr22m, then a 1mflush 22mshould be issued
              against 1mstdout22m, 1mstderr 22mand any other  open  output  file  before
              doing  the  1mfork22m.  Otherwise  characters from the parent process
              pending in the buffers will be output by  both  the  parent  and
              child processes.

              Note:  If  you  are  1mfork22ming  in a Tk based application you must
              1mexecl 22mbefore doing any window operations in  the  child  or  you
              will receive a 1mBadWindow 22merror from the X server.

              The 1mfork 22mcommand is not available on 1mWindows22m.
