

     VFORK(2)                 HP Integral PC                  VFORK(2)     VFORK(2)                 HP Integral PC                  VFORK(2)     VFORK(2)                 HP Integral PC                  VFORK(2)     VFORK(2)                 HP Integral PC                  VFORK(2)


     NAME     NAME     NAME     NAME
          vfork - spawn a new process in a memory efficient manner

     SYNOPSIS     SYNOPSIS     SYNOPSIS     SYNOPSIS
          vfork()

     HP-UX COMPATABILITY     HP-UX COMPATABILITY     HP-UX COMPATABILITY     HP-UX COMPATABILITY
          Level:  HP-UX/RT
          Origin: UCB

     DESCRIPTION     DESCRIPTION     DESCRIPTION     DESCRIPTION
          Vfork can be used to create a new process without fully
          copying the address space of the old process.  It is useful
          when the purpose of fork(2) would have been to create a new
          system context for an exec. Vfork differs from fork in that
          the child process borrows the parent's memory and thread of
          control until a call to exec(2) or an exit occurs (either by
          a call to exit(2) or abnormally.)  The parent process is
          suspended while the child is using its resources.

          Vfork returns 0 in the child's context and (later) the pid
          of the child in the parent's process.

          Vfork can normally be used just like fork.  It does not
          work, however to return while running in the child's context
          from the procedure which called vfork since the parent's
          eventual return from vfork would then return to a no longer
          existant stack frame.  Be careful, also, to call _exit
          rather than exit if you can't exec, since exit will flush
          and close standard IO channels, and thereby mess up the
          parent process's standard IO data structure.  (Even with
          fork it is wrong to call exit since buffered data would then
          be flushed twice.)

     ERRORS     ERRORS     ERRORS     ERRORS
          Vfork will fail, return -1, and no child process will be
          created if the system-imposed limit on the total number of
          processes under execution would be exceeded [EAGAIN]; if the
          single user process limit would be exceeded [EAGAIN]; or if
          there is not enough system memory for the child process
          [ENOMEM].

     SEE ALSO     SEE ALSO     SEE ALSO     SEE ALSO
          fork(2), exec(2), wait(2)

     NOTES     NOTES     NOTES     NOTES
          To avoid possible deadlock situations, processes which are
          children in the middle of a vfork are never sent SIGTTOU or
          SIGTTIN signals; rather, output or ioctls are allowed and
          input attempts result in an end-of-file indication.

          This call is peculiar to this version of HP-UX.


     Hewlett-Packard               - 1 -            (printed 12/12/84)


     VFORK(2)                 HP Integral PC                  VFORK(2)     VFORK(2)                 HP Integral PC                  VFORK(2)     VFORK(2)                 HP Integral PC                  VFORK(2)     VFORK(2)                 HP Integral PC                  VFORK(2)


          On the HP Integral PC vforked children have a unique 2k
          stack allocated to them.  Stack used beyond this 2k limit is
          shared between child and parent.


     Hewlett-Packard               - 2 -            (printed 12/12/84)