456 lines
14 KiB
Groff
456 lines
14 KiB
Groff
.\" Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
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.\" All rights reserved.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" Portions of this text are reprinted and reproduced in electronic form
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.\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
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.\" Portable Operating System Interface (POSIX), The Open Group Base
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.\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of
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.\" Electrical and Electronics Engineers, Inc and The Open Group. In the
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.\" event of any discrepancy between this version and the original IEEE and
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.\" The Open Group Standard, the original IEEE and The Open Group Standard is
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.\" the referee document. The original Standard can be obtained online at
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.\" http://www.opengroup.org/unix/online.html.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 24, 2008
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.Dt POSIX_SPAWN 3
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.Os
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.Sh NAME
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.Nm posix_spawn ,
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.Nm posix_spawnp
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.Nd "spawn a process"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In spawn.h
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.Ft int
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.Fn posix_spawn "pid_t *restrict pid" "const char *restrict path" "const posix_spawn_file_actions_t *file_actions" "const posix_spawnattr_t *restrict attrp" "char *const argv[restrict]" "char *const envp[restrict]"
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.Ft int
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.Fn posix_spawnp "pid_t *restrict pid" "const char *restrict file" "const posix_spawn_file_actions_t *file_actions" "const posix_spawnattr_t *restrict attrp" "char *const argv[restrict]" "char *const envp[restrict]"
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.Sh DESCRIPTION
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The
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.Fn posix_spawn
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and
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.Fn posix_spawnp
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functions create a new process (child process) from the specified
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process image.
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The new process image is constructed from a regular executable
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file called the new process image file.
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.Pp
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When a C program is executed as the result of this call, it is
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entered as a C-language function call as follows:
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.Bd -literal -offset indent
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int main(int argc, char *argv[]);
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.Ed
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.Pp
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where
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.Fa argc
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is the argument count and
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.Fa argv
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is an array of character pointers to the arguments themselves.
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In addition, the variable:
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.Bd -literal -offset indent
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extern char **environ;
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.Ed
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.Pp
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points to an array of character pointers to
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the environment strings.
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.Pp
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The argument
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.Fa argv
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is an array of character pointers to null-terminated
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strings.
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The last member of this array is a null pointer and is not counted
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in
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.Fa argc .
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These strings constitute the argument list available to the new process
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image.
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The value in
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.Fa argv Ns [0]
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should point to
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a filename that is associated with the process image being started by
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the
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.Fn posix_spawn
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or
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.Fn posix_spawnp
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function.
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.Pp
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The argument
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.Fa envp
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is an array of character pointers to null-terminated strings.
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These strings constitute the environment for the new process image.
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The environment array is terminated by a null pointer.
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.Pp
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The
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.Fa path
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argument to
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.Fn posix_spawn
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is a pathname that identifies the new process image file to execute.
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.Pp
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The
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.Fa file
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parameter to
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.Fn posix_spawnp
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is used to construct a pathname that identifies the new process
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image file.
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If the file parameter contains a slash character, the file parameter
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is used as the pathname for the new process image file.
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Otherwise, the path prefix for this file is obtained by a search
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of the directories passed as the environment variable
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.Dq Ev PATH .
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If this variable is not specified,
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the default path is set according to the
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.Dv _PATH_DEFPATH
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definition in
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.In paths.h ,
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which is set to
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.Dq Ev /usr/bin:/bin .
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.Pp
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If
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.Fa file_actions
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is a null pointer, then file descriptors open in the
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calling process remain open in the child process, except for those
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whose close-on-exec flag
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.Dv FD_CLOEXEC
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is set (see
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.Fn fcntl ) .
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For those
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file descriptors that remain open, all attributes of the corresponding
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open file descriptions, including file locks (see
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.Fn fcntl ) ,
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remain unchanged.
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.Pp
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If
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.Fa file_actions
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is not NULL, then the file descriptors open in the child process are
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those open in the calling process as modified by the spawn file
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actions object pointed to by
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.Fa file_actions
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and the
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.Dv FD_CLOEXEC
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flag of each remaining open file descriptor after the spawn file actions
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have been processed.
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The effective order of processing the spawn file actions are:
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.Bl -enum
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.It
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The set of open file descriptors for the child process initially
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are the same set as is open for the calling process.
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All attributes of the corresponding open file descriptions, including
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file locks (see
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.Fn fcntl ) ,
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remain unchanged.
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.It
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The signal mask, signal default actions, and the effective user and
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group IDs for the child process are changed as specified in the
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attributes object referenced by
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.Fa attrp .
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.It
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The file actions specified by the spawn file actions object are
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performed in the order in which they were added to the spawn file
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actions object.
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.It
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Any file descriptor that has its
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.Dv FD_CLOEXEC
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flag set (see
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.Fn fcntl )
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is closed.
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.El
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.Pp
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The
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.Vt posix_spawnattr_t
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spawn attributes object type is defined in
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.In spawn.h .
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It contains the attributes defined below.
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.Pp
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If the
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.Dv POSIX_SPAWN_SETPGROUP
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flag is set in the spawn-flags attribute of the object referenced by
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.Fa attrp ,
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and the spawn-pgroup attribute of the same object is non-zero, then the
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child's process group is as specified in the spawn-pgroup
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attribute of the object referenced by
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.Fa attrp .
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.Pp
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As a special case, if the
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.Dv POSIX_SPAWN_SETPGROUP
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flag is set in the spawn-flags attribute of the object referenced by
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.Fa attrp ,
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and the spawn-pgroup attribute of the same object is set to zero, then
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the child is in a new process group with a process group ID equal
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to its process ID.
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.Pp
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If the
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.Dv POSIX_SPAWN_SETPGROUP
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flag is not set in the spawn-flags attribute of the object referenced by
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.Fa attrp ,
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the new child process inherits the parent's process group.
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.Pp
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If the
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.Dv POSIX_SPAWN_SETSCHEDPARAM
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flag is set in the spawn-flags attribute of the object referenced by
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.Fa attrp ,
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but
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.Dv POSIX_SPAWN_SETSCHEDULER
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is not set, the new process image initially has the scheduling
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policy of the calling process with the scheduling parameters specified
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in the spawn-schedparam attribute of the object referenced by
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.Fa attrp .
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.Pp
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If the
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.Dv POSIX_SPAWN_SETSCHEDULER
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flag is set in the spawn-flags attribute of the object referenced by
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.Fa attrp
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(regardless of the setting of the
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.Dv POSIX_SPAWN_SETSCHEDPARAM
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flag), the new process image initially has the scheduling policy
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specified in the spawn-schedpolicy attribute of the object referenced by
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.Fa attrp
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and the scheduling parameters specified in the spawn-schedparam
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attribute of the same object.
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.Pp
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The
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.Dv POSIX_SPAWN_RESETIDS
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flag in the spawn-flags attribute of the object referenced by
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.Fa attrp
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governs the effective user ID of the child process.
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If this flag is not set, the child process inherits the parent
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process' effective user ID.
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If this flag is set, the child process' effective user ID is reset
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to the parent's real user ID.
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In either case, if the set-user-ID mode bit of the new process image
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file is set, the effective user ID of the child process becomes
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that file's owner ID before the new process image begins execution.
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.Pp
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The
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.Dv POSIX_SPAWN_RESETIDS
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flag in the spawn-flags attribute of the object referenced by
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.Fa attrp
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also governs the effective group ID of the child process.
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If this flag is not set, the child process inherits the parent
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process' effective group ID.
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If this flag is set, the child process' effective group ID is
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reset to the parent's real group ID.
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In either case, if the set-group-ID mode bit of the new process image
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file is set, the effective group ID of the child process becomes
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that file's group ID before the new process image begins execution.
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.Pp
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If the
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.Dv POSIX_SPAWN_SETSIGMASK
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flag is set in the spawn-flags attribute of the object referenced by
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.Fa attrp ,
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the child process initially has the signal mask specified in the
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spawn-sigmask attribute of the object referenced by
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.Fa attrp .
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.Pp
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If the
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.Dv POSIX_SPAWN_SETSIGDEF
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flag is set in the spawn-flags attribute of the object referenced by
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.Fa attrp ,
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the signals specified in the spawn-sigdefault attribute of the same
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object is set to their default actions in the child process.
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Signals set to the default action in the parent process is set to
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the default action in the child process.
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.Pp
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Signals set to be caught by the calling process is set to the
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default action in the child process.
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.Pp
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Signals set to be ignored by the calling process image is set to
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be ignored by the child process, unless otherwise specified by the
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.Dv POSIX_SPAWN_SETSIGDEF
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flag being set in the spawn-flags attribute of the object referenced by
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.Fa attrp
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and the signals being indicated in the spawn-sigdefault attribute
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of the object referenced by
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.Fa attrp .
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.Pp
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If the value of the
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.Fa attrp
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pointer is NULL, then the default values are used.
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.Pp
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All process attributes, other than those influenced by the attributes
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set in the object referenced by
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.Fa attrp
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as specified above or by the file descriptor manipulations specified in
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.Fa file_actions ,
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appear in the new process image as though
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.Fn vfork
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had been called to create a child process and then
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.Fn execve
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had been called by the child process to execute the new process image.
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.Pp
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The implementation uses vfork(), thus the fork handlers are not run when
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.Fn posix_spawn
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or
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.Fn posix_spawnp
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is called.
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.Sh RETURN VALUES
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Upon successful completion,
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.Fn posix_spawn
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and
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.Fn posix_spawnp
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return the process ID of the child process to the parent process,
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in the variable pointed to by a non-NULL
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.Fa pid
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argument, and return zero as the function return value.
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Otherwise, no child process is created, no value is stored into
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the variable pointed to by
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.Fa pid ,
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and an error number is returned as the function return value to
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indicate the error.
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If the
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.Fa pid
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argument is a null pointer, the process ID of the child is not returned
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to the caller.
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.Sh ERRORS
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.Bl -enum
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.It
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If
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.Fn posix_spawn
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and
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.Fn posix_spawnp
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fail for any of the reasons that would cause
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.Fn vfork
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or one of the
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.Nm exec
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to fail, an error value is returned as described by
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.Fn vfork
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and
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.Nm exec ,
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respectively (or, if the error occurs after the calling process successfully
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returns, the child process exits with exit status 127).
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.It
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If
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.Nm POSIX_SPAWN_SETPGROUP
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is set in the spawn-flags attribute of the object referenced by attrp, and
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.Fn posix_spawn
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or
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.Fn posix_spawnp
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fails while changing the child's process group, an error value is returned as
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described by
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.Fn setpgid
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(or, if the error occurs after the calling process successfully returns,
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the child process exits with exit status 127).
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.It
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If
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.Nm POSIX_SPAWN_SETSCHEDPARAM
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is set and
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.Nm POSIX_SPAWN_SETSCHEDULER
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is not set in the spawn-flags attribute of the object referenced by attrp, then
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if
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.Fn posix_spawn
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or
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.Fn posix_spawnp
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fails for any of the reasons that would cause
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.Fn sched_setparam
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to fail, an error value is returned as described by
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.Fn sched_setparam
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(or, if the error occurs after the calling process successfully returns, the
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child process exits with exit status 127).
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.It
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If
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.Nm POSIX_SPAWN_SETSCHEDULER
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is set in the spawn-flags attribute of the object referenced by attrp, and if
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.Fn posix_spawn
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or
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.Fn posix_spawnp
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fails for any of the reasons that would cause
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.Fn sched_setscheduler
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to fail, an error value is returned as described by
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.Fn sched_setscheduler
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(or, if the error occurs after the calling process successfully returns,
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the child process exits with exit status 127).
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.It
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If the
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.Fa file_actions
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argument is not NULL, and specifies any close, dup2, or open actions to be
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performed, and if
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.Fn posix_spawn
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or
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.Fn posix_spawnp
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fails for any of the reasons that would cause
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.Fn close ,
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.Fn dup2 ,
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or
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.Fn open
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to fail, an error value is returned as described by
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.Fn close ,
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.Fn dup2 ,
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and
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.Fn open ,
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respectively (or, if the error occurs after the calling process successfully
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returns, the child process exits with exit status 127). An open file action
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may, by itself, result in any of the errors described by
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.Fn close
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or
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.Fn dup2 ,
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in addition to those described by
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.Fn open .
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.El
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.Sh SEE ALSO
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.Xr close 2 ,
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.Xr dup2 2 ,
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.Xr execve 2 ,
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.Xr fcntl 2 ,
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.Xr open 2 ,
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.Xr posix_spawn_file_actions_addclose 3 ,
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.Xr posix_spawn_file_actions_adddup2 3 ,
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.Xr posix_spawn_file_actions_addopen 3 ,
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.Xr posix_spawn_file_actions_destroy 3 ,
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.Xr posix_spawn_file_actions_init 3 ,
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.Xr posix_spawnattr_destroy 3 ,
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.Xr posix_spawnattr_getflags 3 ,
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.Xr posix_spawnattr_getpgroup 3 ,
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.Xr posix_spawnattr_getschedparam 3 ,
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.Xr posix_spawnattr_getschedpolicy 3 ,
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.Xr posix_spawnattr_getsigdefault 3 ,
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.Xr posix_spawnattr_getsigmask 3 ,
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.Xr posix_spawnattr_init 3 ,
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.Xr posix_spawnattr_setflags 3 ,
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.Xr posix_spawnattr_setpgroup 3 ,
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.Xr posix_spawnattr_setschedparam 3 ,
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.Xr posix_spawnattr_setschedpolicy 3 ,
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.Xr posix_spawnattr_setsigdefault 3 ,
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.Xr posix_spawnattr_setsigmask 3 ,
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.Xr sched_setparam 2 ,
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.Xr sched_setscheduler 2 ,
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.Xr setpgid 2 ,
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.Xr vfork 2
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.Sh STANDARDS
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The
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.Fn posix_spawn
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and
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.Fn posix_spawnp
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functions conform to
|
|
.St -p1003.1-2001 .
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|
.Sh HISTORY
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|
The
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.Fn posix_spawn
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and
|
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.Fn posix_spawnp
|
|
functions first appeared in
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|
.Fx 8.0 .
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|
.Sh AUTHORS
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|
.An Ed Schouten Aq ed@FreeBSD.org
|