1.\" $NetBSD: vfork.2,v 1.7 1997/06/30 18:42:51 phil Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)vfork.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 30, 1997 37.Dt VFORK 2 38.Os BSD 4 39.Sh NAME 40.Nm vfork 41.Nd spawn new process and block parent 42.Sh SYNOPSIS 43.Fd #include <unistd.h> 44.Ft pid_t 45.Fn vfork void 46.Sh DESCRIPTION 47.Fn Vfork 48was originally used to create new processes without fully copying the address 49space of the old process, which is horrendously inefficient in a paged 50environment. It was useful when the purpose of 51.Xr fork 2 52would have been to create a new system context for an 53.Xr execve . 54It is the case that 55.Xr fork 56is now efficient, even in the above case, so that the need for 57.Fn vfork 58is diminished. 59.Fn Vfork 60differs from 61.Xr fork 62in that the parent is suspended until the child makes a call to 63.Xr execve 2 64or an exit (either by a call to 65.Xr exit 2 66or abnormally.) 67.Pp 68.Fn Vfork 69returns 0 in the child's context and (later) the pid of the child in 70the parent's context. 71.Sh SEE ALSO 72.Xr fork 2 , 73.Xr execve 2 , 74.Xr sigaction 2 , 75.Xr wait 2 , 76.Sh DIAGNOSTICS 77Same as for 78.Xr fork . 79.Sh BUGS 80.Pp 81To avoid a possible deadlock situation, 82processes that are children in the middle 83of a 84.Fn vfork 85are never sent 86.Dv SIGTTOU 87or 88.Dv SIGTTIN 89signals; rather, 90output or 91.Xr ioctl 2 92calls 93are allowed 94and input attempts result in an end-of-file indication. 95.Sh HISTORY 96The 97.Fn vfork 98function call appeared in 99.Bx 3.0 . 100