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342cc934a3
Currently there is no proper way to set the controlling terminal through
posix_spawn in race free manner [1]. This forces shell implementations
to keep using fork+exec when launching background process groups,
even when using posix_spawn yields better performance.
This patch adds a new GNU extension so the creating process can
configure the created process terminal group. This is done with a new
flag, POSIX_SPAWN_TCSETPGROUP, along with two new attribute functions:
posix_spawnattr_tcsetpgrp_np, and posix_spawnattr_tcgetpgrp_np.
The function sets a new attribute, spawn-tcgroupfd, that references to
the controlling terminal.
The controlling terminal is set after the spawn-pgroup attribute, and
uses the spawn-tcgroupfd along with current creating process group
(so it is composable with POSIX_SPAWN_SETPGROUP).
To create a process and set the controlling terminal, one can use the
following sequence:
posix_spawnattr_t attr;
posix_spawnattr_init (&attr);
posix_spawnattr_setflags (&attr, POSIX_SPAWN_TCSETPGROUP);
posix_spawnattr_tcsetpgrp_np (&attr, tcfd);
If the idea is also to create a new process groups:
posix_spawnattr_t attr;
posix_spawnattr_init (&attr);
posix_spawnattr_setflags (&attr, POSIX_SPAWN_TCSETPGROUP
| POSIX_SPAWN_SETPGROUP);
posix_spawnattr_tcsetpgrp_np (&attr, tcfd);
posix_spawnattr_setpgroup (&attr, 0);
The controlling terminal file descriptor is ignored if the new flag is
not set.
This interface is slight different than the one provided by QNX [2],
which only provides the POSIX_SPAWN_TCSETPGROUP flag. The QNX
documentation does not specify how the controlling terminal is obtained
nor how it iteracts with POSIX_SPAWN_SETPGROUP. Since a glibc
implementation is library based, it is more straightforward and avoid
requires additional file descriptor operations to request the caller
to setup the controlling terminal file descriptor (and it also allows
a bit less error handling by posix_spawn).
Checked on x86_64-linux-gnu and i686-linux-gnu.
[1] https://github.com/ksh93/ksh/issues/79
[2] https://www.qnx.com/developers/docs/7.0.0/index.html#com.qnx.doc.neutrino.lib_ref/topic/p/posix_spawn.html
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
243 lines
8.4 KiB
C
243 lines
8.4 KiB
C
/* Definitions for POSIX spawn interface.
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Copyright (C) 2000-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _SPAWN_H
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#define _SPAWN_H 1
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#include <features.h>
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#include <sched.h>
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#include <sys/types.h>
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#include <bits/types/sigset_t.h>
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/* Data structure to contain attributes for thread creation. */
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typedef struct
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{
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short int __flags;
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pid_t __pgrp;
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sigset_t __sd;
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sigset_t __ss;
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struct sched_param __sp;
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int __policy;
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int __ctty_fd;
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int __pad[15];
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} posix_spawnattr_t;
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/* Data structure to contain information about the actions to be
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performed in the new process with respect to file descriptors. */
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typedef struct
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{
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int __allocated;
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int __used;
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struct __spawn_action *__actions;
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int __pad[16];
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} posix_spawn_file_actions_t;
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/* Flags to be set in the `posix_spawnattr_t'. */
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#define POSIX_SPAWN_RESETIDS 0x01
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#define POSIX_SPAWN_SETPGROUP 0x02
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#define POSIX_SPAWN_SETSIGDEF 0x04
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#define POSIX_SPAWN_SETSIGMASK 0x08
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#define POSIX_SPAWN_SETSCHEDPARAM 0x10
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#define POSIX_SPAWN_SETSCHEDULER 0x20
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#ifdef __USE_GNU
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# define POSIX_SPAWN_USEVFORK 0x40
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# define POSIX_SPAWN_SETSID 0x80
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# define POSIX_SPAWN_TCSETPGROUP 0x100
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#endif
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__BEGIN_DECLS
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/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
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Before running the process perform the actions described in FILE-ACTIONS.
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This function is a possible cancellation point and therefore not
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marked with __THROW. */
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extern int posix_spawn (pid_t *__restrict __pid,
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const char *__restrict __path,
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const posix_spawn_file_actions_t *__restrict
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__file_actions,
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const posix_spawnattr_t *__restrict __attrp,
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char *const __argv[__restrict_arr],
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char *const __envp[__restrict_arr])
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__nonnull ((2, 5));
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/* Similar to `posix_spawn' but search for FILE in the PATH.
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This function is a possible cancellation point and therefore not
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marked with __THROW. */
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extern int posix_spawnp (pid_t *__pid, const char *__file,
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const posix_spawn_file_actions_t *__file_actions,
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const posix_spawnattr_t *__attrp,
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char *const __argv[], char *const __envp[])
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__nonnull ((2, 5));
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/* Initialize data structure with attributes for `spawn' to default values. */
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extern int posix_spawnattr_init (posix_spawnattr_t *__attr)
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__THROW __nonnull ((1));
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/* Free resources associated with ATTR. */
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extern int posix_spawnattr_destroy (posix_spawnattr_t *__attr)
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__THROW __nonnull ((1));
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/* Store signal mask for signals with default handling from ATTR in
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SIGDEFAULT. */
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extern int posix_spawnattr_getsigdefault (const posix_spawnattr_t *
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__restrict __attr,
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sigset_t *__restrict __sigdefault)
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__THROW __nonnull ((1, 2));
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/* Set signal mask for signals with default handling in ATTR to SIGDEFAULT. */
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extern int posix_spawnattr_setsigdefault (posix_spawnattr_t *__restrict __attr,
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const sigset_t *__restrict
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__sigdefault)
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__THROW __nonnull ((1, 2));
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/* Store signal mask for the new process from ATTR in SIGMASK. */
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extern int posix_spawnattr_getsigmask (const posix_spawnattr_t *__restrict
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__attr,
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sigset_t *__restrict __sigmask)
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__THROW __nonnull ((1, 2));
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/* Set signal mask for the new process in ATTR to SIGMASK. */
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extern int posix_spawnattr_setsigmask (posix_spawnattr_t *__restrict __attr,
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const sigset_t *__restrict __sigmask)
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__THROW __nonnull ((1, 2));
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/* Get flag word from the attribute structure. */
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extern int posix_spawnattr_getflags (const posix_spawnattr_t *__restrict
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__attr,
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short int *__restrict __flags)
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__THROW __nonnull ((1, 2));
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/* Store flags in the attribute structure. */
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extern int posix_spawnattr_setflags (posix_spawnattr_t *_attr,
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short int __flags)
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__THROW __nonnull ((1));
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/* Get process group ID from the attribute structure. */
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extern int posix_spawnattr_getpgroup (const posix_spawnattr_t *__restrict
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__attr, pid_t *__restrict __pgroup)
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__THROW __nonnull ((1, 2));
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/* Store process group ID in the attribute structure. */
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extern int posix_spawnattr_setpgroup (posix_spawnattr_t *__attr,
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pid_t __pgroup)
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__THROW __nonnull ((1));
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/* Get scheduling policy from the attribute structure. */
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extern int posix_spawnattr_getschedpolicy (const posix_spawnattr_t *
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__restrict __attr,
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int *__restrict __schedpolicy)
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__THROW __nonnull ((1, 2));
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/* Store scheduling policy in the attribute structure. */
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extern int posix_spawnattr_setschedpolicy (posix_spawnattr_t *__attr,
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int __schedpolicy)
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__THROW __nonnull ((1));
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/* Get scheduling parameters from the attribute structure. */
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extern int posix_spawnattr_getschedparam (const posix_spawnattr_t *
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__restrict __attr,
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struct sched_param *__restrict
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__schedparam)
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__THROW __nonnull ((1, 2));
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/* Store scheduling parameters in the attribute structure. */
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extern int posix_spawnattr_setschedparam (posix_spawnattr_t *__restrict __attr,
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const struct sched_param *
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__restrict __schedparam)
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__THROW __nonnull ((1, 2));
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#ifdef __USE_GNU
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/* Make the spawned process the foreground process group on the terminal
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associated with FD (which must be a controlling terminal, and still be
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associated with its session). */
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extern int posix_spawnattr_tcsetpgrp_np (posix_spawnattr_t *__attr, int fd)
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__THROW __nonnull ((1));
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/* Return the associated terminal FD in the attribute structure. */
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extern int posix_spawnattr_tcgetpgrp_np (const posix_spawnattr_t *
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__restrict __attr, int *fd)
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__THROW __nonnull ((1, 2));
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#endif
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/* Initialize data structure for file attribute for `spawn' call. */
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extern int posix_spawn_file_actions_init (posix_spawn_file_actions_t *
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__file_actions)
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__THROW __nonnull ((1));
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/* Free resources associated with FILE-ACTIONS. */
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extern int posix_spawn_file_actions_destroy (posix_spawn_file_actions_t *
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__file_actions)
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__THROW __nonnull ((1));
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/* Add an action to FILE-ACTIONS which tells the implementation to call
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`open' for the given file during the `spawn' call. */
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extern int posix_spawn_file_actions_addopen (posix_spawn_file_actions_t *
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__restrict __file_actions,
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int __fd,
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const char *__restrict __path,
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int __oflag, mode_t __mode)
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__THROW __nonnull ((1, 3));
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/* Add an action to FILE-ACTIONS which tells the implementation to call
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`close' for the given file descriptor during the `spawn' call. */
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extern int posix_spawn_file_actions_addclose (posix_spawn_file_actions_t *
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__file_actions, int __fd)
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__THROW __nonnull ((1));
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/* Add an action to FILE-ACTIONS which tells the implementation to call
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`dup2' for the given file descriptors during the `spawn' call. */
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extern int posix_spawn_file_actions_adddup2 (posix_spawn_file_actions_t *
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__file_actions,
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int __fd, int __newfd)
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__THROW __nonnull ((1));
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#ifdef __USE_GNU
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/* Add an action changing the directory to PATH during spawn. This
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affects the subsequent file actions. */
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extern int posix_spawn_file_actions_addchdir_np (posix_spawn_file_actions_t *
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__restrict __actions,
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const char *__restrict __path)
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__THROW __nonnull ((1, 2));
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/* Add an action changing the directory to FD during spawn. This
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affects the subsequent file actions. FD is not duplicated and must
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be open when the file action is executed. */
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extern int posix_spawn_file_actions_addfchdir_np (posix_spawn_file_actions_t *,
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int __fd)
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__THROW __nonnull ((1));
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/* Add an action to close all file descriptor greater than or equal to FROM
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during spawn. This affects the subsequent file actions. */
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extern int
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posix_spawn_file_actions_addclosefrom_np (posix_spawn_file_actions_t *,
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int __from)
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__THROW __nonnull ((1));
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#endif
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__END_DECLS
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#endif /* spawn.h */
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