Add a manual page for fork1(), the kernel's internal fork interface.
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.\" $NetBSD: fork1.9,v 1.1 1998/01/07 00:30:02 thorpej Exp $
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.\"
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.\" Copyright (c) 1998 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
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.\" NASA Ames Research Center.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd January 6, 1998
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.Dt FORK1 9
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.Os NetBSD
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.Sh NAME
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.Nm fork1
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.Nd create a new process
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.Sh SYNOPSIS
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.Ft int
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.Fn "fork1" "struct proc *p1" "int flags" "register_t *retval" "struct proc **rnewprocp"
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.Sh DESCRIPTION
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.Fn fork1
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creates a new process out of
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.Ar p1 ,
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which is assumed to be the current process. This function is used primarily
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to implement the
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.Xr fork 2
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and
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.Xr vfork 2
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system calls.
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.Pp
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The
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.Ar flags
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argument controls the semantics of the fork operation, and is made up of
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the bitwise-OR of the following values:
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.Bl -tag -width FORK_SHAREVM
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.It FORK_PPWAIT
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The parent process will sleep until the child process successfully calls
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.Xr execve 2
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or exits (either by a call to
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.Xr _exit 2
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or abormally).
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.It FORK_SHAREVM
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The child process will share the parent's virtual address space. If this
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flag is not specified, the child will get a copy-on-write snapshot of the
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parent's address space.
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.El
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.Pp
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A
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.Ar flags
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value of 0 indicates a standard fork operation.
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.Pp
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The
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.Ar retval
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argument is provided for the use of system call stubs. If
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.Ar retval
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is not NULL, it will hold the following values after successful completion
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of the fork operation:
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.Bl -tag -width retval[0]
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.It Ar retval[0]
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This will contain the pid of the child process.
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.It Ar retval[1]
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In the parent process, this will contain the value 0. In the child process,
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this will contain 1.
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.El
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.Pp
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User level system call stubs typically subtract 1 from
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.Ar retval[1]
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and bitwise-AND it with
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.Ar retval[0] ,
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thus returning the pid to the parent process and 0 to the child.
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.Pp
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If
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.Ar rnewprocp
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is not NULL,
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.Ar *rnewprocp
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will point to the newly created process upon successful completion of
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the fork operation.
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.Sh RETURN VALUES
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Upon successful completion of the fork operation,
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.Fn fork1
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returns 0. Otherwise, the following error values are returned:
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.Bl -tag -width [EAGAIN]
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.It Bq Er EAGAIN
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The limit on the total number of system processes would be exceeded.
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.It Bq Er EAGAIN
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The limit
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.Dv RLIMIT_NPROC
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on the total number of processes under execution by this
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user id would be exceeded.
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.El
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.Sh SEE ALSO
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.Xr execve 2 ,
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.Xr fork 2 ,
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.Xr vfork 2
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