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author | davidxu <davidxu@FreeBSD.org> | 2008-07-28 02:22:19 +0000 |
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committer | davidxu <davidxu@FreeBSD.org> | 2008-07-28 02:22:19 +0000 |
commit | bcd09d8c858aeed6161450a2b75037304d25ae33 (patch) | |
tree | 75173df4c1ca3d6664791e293a20795209629b51 /lib/libc/gen/posix_spawn.3 | |
parent | 70741e02459ae30ab456a856e67cbb70119beb66 (diff) | |
download | FreeBSD-src-bcd09d8c858aeed6161450a2b75037304d25ae33.zip FreeBSD-src-bcd09d8c858aeed6161450a2b75037304d25ae33.tar.gz |
Add manual pages for posix_spawn() functions.
PR: standards/122051
Diffstat (limited to 'lib/libc/gen/posix_spawn.3')
-rw-r--r-- | lib/libc/gen/posix_spawn.3 | 455 |
1 files changed, 455 insertions, 0 deletions
diff --git a/lib/libc/gen/posix_spawn.3 b/lib/libc/gen/posix_spawn.3 new file mode 100644 index 0000000..afa639e --- /dev/null +++ b/lib/libc/gen/posix_spawn.3 @@ -0,0 +1,455 @@ +.\" Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org> +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" 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. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" Portions of this text are reprinted and reproduced in electronic form +.\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- +.\" Portable Operating System Interface (POSIX), The Open Group Base +.\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of +.\" Electrical and Electronics Engineers, Inc and The Open Group. In the +.\" event of any discrepancy between this version and the original IEEE and +.\" The Open Group Standard, the original IEEE and The Open Group Standard is +.\" the referee document. The original Standard can be obtained online at +.\" http://www.opengroup.org/unix/online.html. +.\" +.\" $FreeBSD$ +.\" +.Dd Mar 24, 2008 +.Dt POSIX_SPAWN 3 +.Os +.Sh NAME +.Nm posix_spawn , +.Nm posix_spawnp +.Nd "spawn a process" +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In spawn.h +.Ft int +.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]" +.Ft int +.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]" +.Sh DESCRIPTION +The +.Fn posix_spawn +and +.Fn posix_spawnp +functions create a new process (child process) from the specified +process image. +The new process image is constructed from a regular executable +file called the new process image file. +.Pp +When a C program is executed as the result of this call, it is +entered as a C-language function call as follows: +.Bd -literal -offset indent +int main(int argc, char *argv[]); +.Ed +.Pp +where +.Fa argc +is the argument count and +.Fa argv +is an array of character pointers to the arguments themselves. +In addition, the variable: +.Bd -literal -offset indent +extern char **environ; +.Ed +.Pp +points to an array of character pointers to +the environment strings. +.Pp +The argument +.Fa argv +is an array of character pointers to null-terminated +strings. +The last member of this array is a null pointer and is not counted +in +.Fa argc . +These strings constitute the argument list available to the new process +image. +The value in +.Fa argv Ns [0] +should point to +a filename that is associated with the process image being started by +the +.Fn posix_spawn +or +.Fn posix_spawnp +function. +.Pp +The argument +.Fa envp +is an array of character pointers to null-terminated strings. +These strings constitute the environment for the new process image. +The environment array is terminated by a null pointer. +.Pp +The +.Fa path +argument to +.Fn posix_spawn +is a pathname that identifies the new process image file to execute. +.Pp +The +.Fa file +parameter to +.Fn posix_spawnp +is used to construct a pathname that identifies the new process +image file. +If the file parameter contains a slash character, the file parameter +is used as the pathname for the new process image file. +Otherwise, the path prefix for this file is obtained by a search +of the directories passed as the environment variable +.Dq Ev PATH . +If this variable is not specified, +the default path is set according to the +.Dv _PATH_DEFPATH +definition in +.In paths.h , +which is set to +.Dq Ev /usr/bin:/bin . +.Pp +If +.Fa file_actions +is a null pointer, then file descriptors open in the +calling process remain open in the child process, except for those +whose close-on-exec flag +.Dv FD_CLOEXEC +is set (see +.Fn fcntl ) . +For those +file descriptors that remain open, all attributes of the corresponding +open file descriptions, including file locks (see +.Fn fcntl ) , +remain unchanged. +.Pp +If +.Fa file_actions +is not NULL, then the file descriptors open in the child process are +those open in the calling process as modified by the spawn file +actions object pointed to by +.Fa file_actions +and the +.Dv FD_CLOEXEC +flag of each remaining open file descriptor after the spawn file actions +have been processed. +The effective order of processing the spawn file actions are: +.Bl -enum +.It +The set of open file descriptors for the child process initially +are the same set as is open for the calling process. +All attributes of the corresponding open file descriptions, including +file locks (see +.Fn fcntl ) , +remain unchanged. +.It +The signal mask, signal default actions, and the effective user and +group IDs for the child process are changed as specified in the +attributes object referenced by +.Fa attrp . +.It +The file actions specified by the spawn file actions object are +performed in the order in which they were added to the spawn file +actions object. +.It +Any file descriptor that has its +.Dv FD_CLOEXEC +flag set (see +.Fn fcntl ) +is closed. +.El +.Pp +The +.Vt posix_spawnattr_t +spawn attributes object type is defined in +.In spawn.h . +It contains the attributes defined below. +.Pp +If the +.Dv POSIX_SPAWN_SETPGROUP +flag is set in the spawn-flags attribute of the object referenced by +.Fa attrp , +and the spawn-pgroup attribute of the same object is non-zero, then the +child's process group is as specified in the spawn-pgroup +attribute of the object referenced by +.Fa attrp . +.Pp +As a special case, if the +.Dv POSIX_SPAWN_SETPGROUP +flag is set in the spawn-flags attribute of the object referenced by +.Fa attrp , +and the spawn-pgroup attribute of the same object is set to zero, then +the child is in a new process group with a process group ID equal +to its process ID. +.Pp +If the +.Dv POSIX_SPAWN_SETPGROUP +flag is not set in the spawn-flags attribute of the object referenced by +.Fa attrp , +the new child process inherits the parent's process group. +.Pp +If the +.Dv POSIX_SPAWN_SETSCHEDPARAM +flag is set in the spawn-flags attribute of the object referenced by +.Fa attrp , +but +.Dv POSIX_SPAWN_SETSCHEDULER +is not set, the new process image initially has the scheduling +policy of the calling process with the scheduling parameters specified +in the spawn-schedparam attribute of the object referenced by +.Fa attrp . +.Pp +If the +.Dv POSIX_SPAWN_SETSCHEDULER +flag is set in the spawn-flags attribute of the object referenced by +.Fa attrp +(regardless of the setting of the +.Dv POSIX_SPAWN_SETSCHEDPARAM +flag), the new process image initially has the scheduling policy +specified in the spawn-schedpolicy attribute of the object referenced by +.Fa attrp +and the scheduling parameters specified in the spawn-schedparam +attribute of the same object. +.Pp +The +.Dv POSIX_SPAWN_RESETIDS +flag in the spawn-flags attribute of the object referenced by +.Fa attrp +governs the effective user ID of the child process. +If this flag is not set, the child process inherits the parent +process' effective user ID. +If this flag is set, the child process' effective user ID is reset +to the parent's real user ID. +In either case, if the set-user-ID mode bit of the new process image +file is set, the effective user ID of the child process becomes +that file's owner ID before the new process image begins execution. +.Pp +The +.Dv POSIX_SPAWN_RESETIDS +flag in the spawn-flags attribute of the object referenced by +.Fa attrp +also governs the effective group ID of the child process. +If this flag is not set, the child process inherits the parent +process' effective group ID. +If this flag is set, the child process' effective group ID is +reset to the parent's real group ID. +In either case, if the set-group-ID mode bit of the new process image +file is set, the effective group ID of the child process becomes +that file's group ID before the new process image begins execution. +.Pp +If the +.Dv POSIX_SPAWN_SETSIGMASK +flag is set in the spawn-flags attribute of the object referenced by +.Fa attrp , +the child process initially has the signal mask specified in the +spawn-sigmask attribute of the object referenced by +.Fa attrp . +.Pp +If the +.Dv POSIX_SPAWN_SETSIGDEF +flag is set in the spawn-flags attribute of the object referenced by +.Fa attrp , +the signals specified in the spawn-sigdefault attribute of the same +object is set to their default actions in the child process. +Signals set to the default action in the parent process is set to +the default action in the child process. +.Pp +Signals set to be caught by the calling process is set to the +default action in the child process. +.Pp +Signals set to be ignored by the calling process image is set to +be ignored by the child process, unless otherwise specified by the +.Dv POSIX_SPAWN_SETSIGDEF +flag being set in the spawn-flags attribute of the object referenced by +.Fa attrp +and the signals being indicated in the spawn-sigdefault attribute +of the object referenced by +.Fa attrp . +.Pp +If the value of the +.Fa attrp +pointer is NULL, then the default values are used. +.Pp +All process attributes, other than those influenced by the attributes +set in the object referenced by +.Fa attrp +as specified above or by the file descriptor manipulations specified in +.Fa file_actions , +appear in the new process image as though +.Fn vfork +had been called to create a child process and then +.Fn execve +had been called by the child process to execute the new process image. +.Pp +The implementation uses vfork(), thus the fork handlers are not run when +.Fn posix_spawn +or +.Fn posix_spawnp +is called. +.Sh RETURN VALUES +Upon successful completion, +.Fn posix_spawn +and +.Fn posix_spawnp +return the process ID of the child process to the parent process, +in the variable pointed to by a non-NULL +.Fa pid +argument, and return zero as the function return value. +Otherwise, no child process is created, no value is stored into +the variable pointed to by +.Fa pid , +and an error number is returned as the function return value to +indicate the error. +If the +.Fa pid +argument is a null pointer, the process ID of the child is not returned +to the caller. +.Sh ERRORS +.Bl -enum +.It +If +.Fn posix_spawn +and +.Fn posix_spawnp +fail for any of the reasons that would cause +.Fn vfork +or one of the +.Nm exec +to fail, an error value is returned as described by +.Fn vfork +and +.Nm exec , +respectively (or, if the error occurs after the calling process successfully +returns, the child process exits with exit status 127). +.It +If +.Nm POSIX_SPAWN_SETPGROUP +is set in the spawn-flags attribute of the object referenced by attrp, and +.Fn posix_spawn +or +.Fn posix_spawnp +fails while changing the child's process group, an error value is returned as +described by +.Fn setpgid +(or, if the error occurs after the calling process successfully returns, +the child process exits with exit status 127). +.It +If +.Nm POSIX_SPAWN_SETSCHEDPARAM +is set and +.Nm POSIX_SPAWN_SETSCHEDULER +is not set in the spawn-flags attribute of the object referenced by attrp, then +if +.Fn posix_spawn +or +.Fn posix_spawnp +fails for any of the reasons that would cause +.Fn sched_setparam +to fail, an error value is returned as described by +.Fn sched_setparam +(or, if the error occurs after the calling process successfully returns, the +child process exits with exit status 127). +.It +If +.Nm POSIX_SPAWN_SETSCHEDULER +is set in the spawn-flags attribute of the object referenced by attrp, and if +.Fn posix_spawn +or +.Fn posix_spawnp +fails for any of the reasons that would cause +.Fn sched_setscheduler +to fail, an error value is returned as described by +.Fn sched_setscheduler +(or, if the error occurs after the calling process successfully returns, +the child process exits with exit status 127). +.It +If the +.Fa file_actions +argument is not NULL, and specifies any close, dup2, or open actions to be +performed, and if +.Fn posix_spawn +or +.Fn posix_spawnp +fails for any of the reasons that would cause +.Fn close , +.Fn dup2 , +or +.Fn open +to fail, an error value is returned as described by +.Fn close , +.Fn dup2 , +and +.Fn open , +respectively (or, if the error occurs after the calling process successfully +returns, the child process exits with exit status 127). An open file action +may, by itself, result in any of the errors described by +.Fn close +or +.Fn dup2 , +in addition to those described by +.Fn open . +.El +.Sh SEE ALSO +.Xr close 2 , +.Xr dup2 2 , +.Xr execve 2 , +.Xr fcntl 2 , +.Xr open 2 , +.Xr posix_spawn_file_actions_addclose 3 , +.Xr posix_spawn_file_actions_adddup2 3 , +.Xr posix_spawn_file_actions_addopen 3 , +.Xr posix_spawn_file_actions_destroy 3 , +.Xr posix_spawn_file_actions_init 3 , +.Xr posix_spawnattr_destroy 3 , +.Xr posix_spawnattr_getflags 3 , +.Xr posix_spawnattr_getpgroup 3 , +.Xr posix_spawnattr_getschedparam 3 , +.Xr posix_spawnattr_getschedpolicy 3 , +.Xr posix_spawnattr_getsigdefault 3 , +.Xr posix_spawnattr_getsigmask 3 , +.Xr posix_spawnattr_init 3 , +.Xr posix_spawnattr_setflags 3 , +.Xr posix_spawnattr_setpgroup 3 , +.Xr posix_spawnattr_setschedparam 3 , +.Xr posix_spawnattr_setschedpolicy 3 , +.Xr posix_spawnattr_setsigdefault 3 , +.Xr posix_spawnattr_setsigmask 3 , +.Xr sched_setparam 2 , +.Xr sched_setscheduler 2 , +.Xr setpgid 2 , +.Xr vfork 2 +.Sh STANDARDS +The +.Fn posix_spawn +and +.Fn posix_spawnp +functions conform to +.St -p1003.1-2001 . +.Sh HISTORY +The +.Fn posix_spawn +and +.Fn posix_spawnp +functions first appeared in +.Fx 8.0 . +.Sh AUTHORS +.An Ed Schouten Aq Ed Schouten ed@FreeBSD.org |