vfork man page on HP-UX

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vfork(2)							      vfork(2)

       vfork - spawn new process; share virtual memory

       is  a  higher  performance  version of that is provided on some systems
       where a performance advantage can be attained.

       If the calling process  is  multi-threaded,  the	 newly	created	 child
       process will only contain one thread. This one thread will be a copy of
       the thread calling

       differs from only in that the child process can	share  code  and  data
       with  the calling process (parent process).  This speeds cloning activ‐
       ity significantly at a risk to the integrity of the parent  process  if
       is misused.

       The  use	 of  for any purpose except as a prelude to an immediate or is
       not supported.  Any program that relies upon  the  differences  between
       and is not portable across HP-UX systems.

       All  HP-UX implementations must provide the entry but it is permissible
       for them to treat it identically to On some implementations the two are
       not  distinguished because the implementation is as efficient as possi‐
       ble.  Other versions may do the same to avoid the overhead of  support‐
       ing two similar calls.

       can  be	used to create new processes without fully copying the address
       space of the old process.  If a forked process is simply going to do an
       (see exec(2)), the data space copied from the parent to the child by is
       not used.  This is particularly inefficient  in	a  paged  environment,
       making  particularly  useful.   Depending upon the size of the parent's
       data space, can give a significant performance improvement over

       differs from in that the child borrows the parent's memory  and	thread
       of  control  until  a call to or an exit (either by a call to or abnor‐
       mally (see exec(2) and exit(2)).	 The parent process is suspended while
       the child is using its resources.

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

       can normally be used just like It does not  work,  however,  to	return
       while  running  in  the child's context from the procedure which called
       since the eventual return from would then return to a no	 longer	 exis‐
       tent stack frame.

       The  window  begins  at	the call and ends when the child completes its

       Upon successful completion, returns a value of 0 to the	child  process
       and  returns the process ID of the child process to the parent process.
       Otherwise, a value of −1 is returned to the parent, no child process is
       created, and is set to indicate the error.

       fails  and  no  child process is created if any of the following condi‐
       tions are encountered:

	      The system-wide limit on the total  number  of  processes	 under
			     would be exceeded.

	      The  system-imposed limit on the total number of processes under
			     by a single user would be exceeded.

	      There is insufficient swap space and/or physical memory
			     available to create the new process.

       Process times for the parent and child processes within the window  may
       be inaccurate.

	      Parent and child processes share the same stack space within the
	      window.  If the size of the stack has been changed  within  this
	      window  by the child process (return from or call to a function,
	      for example), it is likely that the parent and  child  processes
	      will be killed with signal or

	      In the window, a call to (see signal(2) that installs a catching
	      function can affect handling of the signal by the	 parent.   The
	      parent  is not affected if the handling is being set to or or if
	      is used (see sigaction(2)).

       was developed by the University of California, Berkeley.

       exec(2), exit(2), fork(2), sigaction(2), wait(2).


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