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NetBSD 6.1.5 - man page for posix_spawn (netbsd section 3)

POSIX_SPAWN(3)			   BSD Library Functions Manual 		   POSIX_SPAWN(3)

NAME
     posix_spawn, posix_spawnp -- spawn a process

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <spawn.h>

     int
     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]);

     int
     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]);

DESCRIPTION
     The posix_spawn() and 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.

     When a C program is executed as the result of this call, it is entered as a C-language func-
     tion call as follows:

	   int main(int argc, char *argv[]);

     where argc is the argument count and argv is an array of character pointers to the arguments
     themselves.  In addition, the variable:

	   extern char **environ;

     points to an array of character pointers to the environment strings.

     The argument 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 argc.  These strings constitute
     the argument list available to the new process image.  The value in argv[0] should point to
     a filename that is associated with the process image being started by the posix_spawn() or
     posix_spawnp() function.

     The argument 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 ter-
     minated by a null pointer.

     The path argument to posix_spawn() is a pathname that identifies the new process image file
     to execute.

     The file parameter to 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 ``PATH''.
     If this variable is not specified, the default path is set according to the _PATH_DEFPATH
     definition in <paths.h>, which is set to ``/usr/bin:/bin''.

     If 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 FD_CLOEXEC is set (see
     fcntl()).	For those file descriptors that remain open, all attributes of the corresponding
     open file descriptions, including file locks (see fcntl()), remain unchanged.

     If 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
     file_actions and the 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:

     1.   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 descrip-
	  tions, including file locks (see fcntl()), remain unchanged.

     2.   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 attrp.

     3.   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.

     4.   Any file descriptor that has its FD_CLOEXEC flag set (see fcntl()) is closed.

     The maximum number of file_actions objects is limited to the RLIMIT_NOFILE rlimit times 2.

     The posix_spawnattr_t spawn attributes object type is defined in <spawn.h>.  It contains the
     attributes defined below.

     If the POSIX_SPAWN_SETPGROUP flag is set in the spawn-flags attribute of the object refer-
     enced by 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 attrp.

     As a special case, if the POSIX_SPAWN_SETPGROUP flag is set in the spawn-flags attribute of
     the object referenced by 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.

     If the POSIX_SPAWN_SETPGROUP flag is not set in the spawn-flags attribute of the object ref-
     erenced by attrp, the new child process inherits the parent's process group.

     If the POSIX_SPAWN_SETSCHEDPARAM flag is set in the spawn-flags attribute of the object ref-
     erenced by attrp, but 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 attrp.

     If the POSIX_SPAWN_SETSCHEDULER flag is set in the spawn-flags attribute of the object ref-
     erenced by attrp (regardless of the setting of the POSIX_SPAWN_SETSCHEDPARAM flag), the new
     process image initially has the scheduling policy specified in the spawn-schedpolicy
     attribute of the object referenced by attrp and the scheduling parameters specified in the
     spawn-schedparam attribute of the same object.

     The POSIX_SPAWN_RESETIDS flag in the spawn-flags attribute of the object referenced by 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.

     The POSIX_SPAWN_RESETIDS flag in the spawn-flags attribute of the object referenced by 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 execu-
     tion.

     If the POSIX_SPAWN_SETSIGMASK flag is set in the spawn-flags attribute of the object refer-
     enced by attrp, the child process initially has the signal mask specified in the spawn-sig-
     mask attribute of the object referenced by attrp.

     If the POSIX_SPAWN_SETSIGDEF flag is set in the spawn-flags attribute of the object refer-
     enced by 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.

     Signals set to be caught by the calling process is set to the default action in the child
     process.

     Signals set to be ignored by the calling process image is set to be ignored by the child
     process, unless otherwise specified by the POSIX_SPAWN_SETSIGDEF flag being set in the
     spawn-flags attribute of the object referenced by attrp and the signals being indicated in
     the spawn-sigdefault attribute of the object referenced by attrp.

     If the value of the attrp pointer is NULL, then the default values are used.

     All process attributes, other than those influenced by the attributes set in the object ref-
     erenced by attrp as specified above or by the file descriptor manipulations specified in
     file_actions, appear in the new process image as though vfork() had been called to create a
     child process and then execve() had been called by the child process to execute the new
     process image.

     The implementation uses vfork(), thus the fork handlers are not run when posix_spawn() or
     posix_spawnp() is called.

RETURN VALUES
     Upon successful completion, posix_spawn() and posix_spawnp() return the process ID of the
     child process to the parent process, in the variable pointed to by a non-NULL 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 pid, and an error number is returned as the
     function return value to indicate the error.  If the pid argument is a null pointer, the
     process ID of the child is not returned to the caller.

ERRORS
     1.   If posix_spawn() and posix_spawnp() fail for any of the reasons that would cause
	  vfork() or one of the exec to fail, an error value is returned as described by vfork()
	  and exec, respectively (or, if the error occurs after the calling process successfully
	  returns, the child process exits with exit status 127).

     2.   If POSIX_SPAWN_SETPGROUP is set in the spawn-flags attribute of the object referenced
	  by attrp, and posix_spawn() or posix_spawnp() fails while changing the child's process
	  group, an error value is returned as described by setpgid() (or, if the error occurs
	  after the calling process successfully returns, the child process exits with exit sta-
	  tus 127).

     3.   If POSIX_SPAWN_SETSCHEDPARAM is set and POSIX_SPAWN_SETSCHEDULER is not set in the
	  spawn-flags attribute of the object referenced by attrp, then if posix_spawn() or
	  posix_spawnp() fails for any of the reasons that would cause sched_setparam() to fail,
	  an error value is returned as described by sched_setparam() (or, if the error occurs
	  after the calling process successfully returns, the child process exits with exit sta-
	  tus 127).

     4.   If POSIX_SPAWN_SETSCHEDULER is set in the spawn-flags attribute of the object refer-
	  enced by attrp, and if posix_spawn() or posix_spawnp() fails for any of the reasons
	  that would cause sched_setscheduler() to fail, an error value is returned as described
	  by sched_setscheduler() (or, if the error occurs after the calling process successfully
	  returns, the child process exits with exit status 127).

     5.   If the file_actions argument is not NULL, and specifies any close(), dup2(), or open()
	  actions to be performed, and if posix_spawn() or posix_spawnp() fails for any of the
	  reasons that would cause close(), dup2(), or open() to fail, an error value is returned
	  as described by close(), dup2(), and open(), respectively (or, if the error occurs
	  after the calling process successfully returns, the child process exits with exit sta-
	  tus 127). An open file action may, by itself, result in any of the errors described by
	  close() or dup2(), in addition to those described by open().	Finally, if the number of
	  file_actions objects exceeds the allowed limit, EINVAL is returned.

SEE ALSO
     close(2), dup2(2), execve(2), fcntl(2), open(2), setpgid(2), vfork(2),
     posix_spawn_file_actions_addclose(3), posix_spawn_file_actions_adddup2(3),
     posix_spawn_file_actions_addopen(3), posix_spawn_file_actions_destroy(3),
     posix_spawn_file_actions_init(3), posix_spawnattr_destroy(3), posix_spawnattr_getflags(3),
     posix_spawnattr_getpgroup(3), posix_spawnattr_getschedparam(3),
     posix_spawnattr_getschedpolicy(3), posix_spawnattr_getsigdefault(3),
     posix_spawnattr_getsigmask(3), posix_spawnattr_init(3), posix_spawnattr_setflags(3),
     posix_spawnattr_setpgroup(3), posix_spawnattr_setschedparam(3),
     posix_spawnattr_setschedpolicy(3), posix_spawnattr_setsigdefault(3),
     posix_spawnattr_setsigmask(3), sched_setparam(3), sched_setscheduler(3)

STANDARDS
     The posix_spawn() and posix_spawnp() functions conform to IEEE Std 1003.1-2001
     (``POSIX.1'').

HISTORY
     The posix_spawn() and posix_spawnp() functions first appeared in FreeBSD 8.0.  The library
     parts were ported and a kernel implementation of posix_spawn() added for NetBSD 6 during
     Google Summer of Code by Charles Zhang and Martin Husemann.

AUTHORS
     Ed Schouten <ed@FreeBSD.org>

BSD					December 20, 2011				      BSD


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