POSIX_SPAWN(3)          NetBSD 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 function call as follows:

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

     where argc is the argument count and argv is an array of character point-
     ers 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 terminated 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 descriptions, 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 per-
          formed 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 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 referenced 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 referenced 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 referenced 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 referenced 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 execution.

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

     If the POSIX_SPAWN_SETSIGDEF flag is set in the spawn-flags attribute of
     the object referenced by attrp, the signals specified in the spawn-sigde-
     fault 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 referenced 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 status 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 status 127).

     4.   If POSIX_SPAWN_SETSCHEDULER is set in the spawn-flags attribute of
          the object referenced 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 status 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().

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>

NetBSD 6.0                     December 20, 2011                    NetBSD 6.0

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