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+.\" Copyright (c) 1980, 1991, 1993
+.\"	The Regents of the University of California.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
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+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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+.\" SUCH DAMAGE.
+.\"
+.\"     @(#)vfork.2	8.1 (Berkeley) 6/4/93
+.\" $FreeBSD$
+.\"
+.Dd November 13, 2009
+.Dt VFORK 2
+.Os
+.Sh NAME
+.Nm vfork
+.Nd create a new process without copying the address space
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In unistd.h
+.Ft pid_t
+.Fn vfork void
+.Sh DESCRIPTION
+The
+.Fn vfork
+system call
+can be used to create new processes without fully copying the address
+space of the old process, which is horrendously inefficient in a paged
+environment.
+It is useful when the purpose of
+.Xr fork 2
+would have been to create a new system context for an
+.Xr execve 2 .
+The
+.Fn vfork
+system call
+differs from
+.Xr fork 2
+in that the child borrows the parent's memory and thread of
+control until a call to
+.Xr execve 2
+or an exit (either by a call to
+.Xr _exit 2
+or abnormally).
+The parent process is suspended while the child is using its resources.
+.Pp
+The
+.Fn vfork
+system call
+returns 0 in the child's context and (later) the pid of the child in
+the parent's context.
+.Pp
+The
+.Fn vfork
+system call
+can normally be used just like
+.Xr fork 2 .
+It does not work, however, to return while running in the child's context
+from the procedure that called
+.Fn vfork
+since the eventual return from
+.Fn vfork
+would then return to a no longer existent stack frame.
+Be careful, also, to call
+.Xr _exit 2
+rather than
+.Xr exit 3
+if you cannot
+.Xr execve 2 ,
+since
+.Xr exit 3
+will flush and close standard I/O channels, and thereby mess up the
+parent processes standard I/O data structures.
+(Even with
+.Xr fork 2
+it is wrong to call
+.Xr exit 3
+since buffered data would then be flushed twice.)
+.Sh RETURN VALUES
+Same as for
+.Xr fork 2 .
+.Sh SEE ALSO
+.Xr execve 2 ,
+.Xr _exit 2 ,
+.Xr fork 2 ,
+.Xr rfork 2 ,
+.Xr sigaction 2 ,
+.Xr wait 2 ,
+.Xr exit 3
+.Sh HISTORY
+The
+.Fn vfork
+system call appeared in
+.Bx 2.9 .
+.Sh BUGS
+To avoid a possible deadlock situation,
+processes that are children in the middle
+of a
+.Fn vfork
+are never sent
+.Dv SIGTTOU
+or
+.Dv SIGTTIN
+signals; rather,
+output or
+.Xr ioctl 2
+calls
+are allowed
+and input attempts result in an end-of-file indication.