vfork(2) - NetBSD Manual Pages

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VFORK(2)                  NetBSD Programmer's Manual                  VFORK(2)


NAME

     vfork - spawn new process and block parent


SYNOPSIS

     #include <unistd.h>

     pid_t
     vfork(void);


DESCRIPTION

     Vfork() was originally used to create new processes without fully copying
     the address space of the old process, which is horrendously inefficient
     in a paged environment.  It was useful when the purpose of fork(2) would
     have been to create a new system context for an execve.  It is the case
     that fork is now efficient, even in the above case, so that the need for
     vfork() is diminished.  Vfork() differs from fork in that the parent is
     suspended until the child makes a call to execve(2) or an exit (either by
     a call to _exit(2) or abnormally.)

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


SEE ALSO

     fork(2),  execve(2),  sigaction(2),  wait(2),


DIAGNOSTICS

     Same as for fork(2).


BUGS

     To avoid a possible deadlock situation, processes that are children in
     the middle of a vfork() are never sent SIGTTOU or SIGTTIN signals;
     rather, output or ioctl(2) calls are allowed and input attempts result in
     an end-of-file indication.


HISTORY

     The vfork() function call appeared in 3.0BSD.

4th Berkeley Distribution        June 30, 1997                               1