1.\" $OpenBSD: fork1.9,v 1.6 2001/08/03 15:21:17 mpech Exp $ 2.\" $NetBSD: fork1.9,v 1.3 1999/03/16 00:40:47 garbled Exp $ 3.\" 4.\" Copyright (c) 1998 The NetBSD Foundation, Inc. 5.\" All rights reserved. 6.\" 7.\" This code is derived from software contributed to The NetBSD Foundation 8.\" by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 9.\" NASA Ames Research Center. 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 3. All advertising materials mentioning features or use of this software 20.\" must display the following acknowledgement: 21.\" This product includes software developed by the NetBSD 22.\" Foundation, Inc. and its contributors. 23.\" 4. Neither the name of The NetBSD Foundation nor the names of its 24.\" contributors may be used to endorse or promote products derived 25.\" from this software without specific prior written permission. 26.\" 27.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37.\" POSSIBILITY OF SUCH DAMAGE. 38.\" 39.Dd January 6, 1998 40.Dt FORK1 9 41.Os 42.Sh NAME 43.Nm fork1 44.Nd create a new process 45.Sh SYNOPSIS 46.Fd #include <sys/types.h> 47.Fd #include <sys/proc.h> 48.Ft int 49.Fn "fork1" "struct proc *p1" "int flags" "void *stack" "size_t stacksize" "register_t *retval" 50.Sh DESCRIPTION 51.Fn fork1 52creates a new process out of 53.Ar p1 , 54which should be the current process. 55This function is used primarily to implement the 56.Xr fork 2 , 57.Xr rfork 2 , 58.Xr vfork 2 59system calls, as well as the 60.Xr kthread_create 9 61function. 62.Pp 63The 64.Ar flags 65argument is used to control the behavior of the fork and is created by 66a bitwise-OR of the following values: 67.Bl -tag -width FORK_SHAREFILES 68.It Dv FORK_FORK 69The call is done by the 70.Xr fork 2 71system call. 72Used only for statistics. 73.It Dv FORK_VFORK 74The call is done by the 75.Xr vfork 2 76system call. 77Used only for statistics. 78.It Dv FORK_RFORK 79The call is done by the 80.Xr rfork 2 81system call. 82Used only for statistics. 83.It Dv FORK_PPWAIT 84Suspend the parent process until the child is terminated (by calling 85.Xr _exit 2 86or abnormally), or makes a call to 87.Xr execve 2 . 88.It Dv FORK_SHAREFILES 89Let the child share the file descriptor table with the parent through 90.Xr fdshare 9 . 91The default behavior is to copy the table through 92.Xr fdcopy 9 . 93.It Dv FORK_CLEANFILES 94The child starts with a clean file descriptor table created by 95.Xr fdinit 9 . 96.It Dv FORK_NOZOMBIE 97The child will be dissociated from the parent and will not leave a status 98for the parent to collect. 99See 100.Xr wait 2 . 101.It Dv FORK_SHAREVM 102The child will share the parent's address space. 103The default behavior is 104that the child gets a copy-on-write copy of the address space. 105.El 106.Pp 107If 108.Fa stack 109is not 110.Dv NULL , 111the area starting at 112.Fa stack 113of extent 114.Fa stacksize 115will be used for the child's stack, instead of cloning the parent's 116stack. 117.Pp 118If 119.Fa retval 120is not 121.Dv NULL , 122it will hold the following values after successful completion 123of the fork operation: 124.Bl -tag -width retval[0] 125.It Fa retval[0] 126This will contain the pid of the child process. 127.It Fa retval[1] 128In the parent process, this will contain the value 0. 129In the child process, this will contain 1. 130.El 131.Sh RETURN VALUES 132Upon successful completion of the fork operation, 133.Fn fork1 134returns 0. 135Otherwise, the following error values are returned: 136.Bl -tag -width [EAGAIN] 137.It Bq Er EAGAIN 138The limit on the total number of system processes would be exceeded. 139.It Bq Er EAGAIN 140The limit 141.Dv RLIMIT_NPROC 142on the total number of processes under execution by this 143user id would be exceeded. 144.El 145.Sh CAVEATS 146The 147.Nm 148function semantics are specific to 149.Ox . 150Other BSD systems have different semantics. 151.Pp 152The system never uses 153.Fn fork1 154with a non-null 155.Fa stack , 156so that feature is not even tested. 157.Sh SEE ALSO 158.Xr execve 2 , 159.Xr fork 2 , 160.Xr rfork 2 , 161.Xr vfork 2 , 162.Xr kthread_create 9 , 163.Xr pfind 9 , 164.Xr psignal 9 165