NAME
posix_spawn_file_actions_addopen
,
posix_spawn_file_actions_adddup2
,
posix_spawn_file_actions_addclose
,
posix_spawn_file_actions_addclosefrom_np
,
posix_spawn_file_actions_addchdir_np
,
posix_spawn_file_actions_addfchdir_np
—
add open, dup2, close, closefrom, or
chdir/fchdir actions to spawn file actions object
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include
<spawn.h>
int
posix_spawn_file_actions_addopen
(posix_spawn_file_actions_t
* file_actions, int fildes,
const char *restrict path, int
oflag, mode_t mode);
int
posix_spawn_file_actions_adddup2
(posix_spawn_file_actions_t
* file_actions, int fildes, int
newfildes);
int
posix_spawn_file_actions_addclose
(posix_spawn_file_actions_t
* file_actions, int fildes);
int
posix_spawn_file_actions_addclosefrom_np
(posix_spawn_file_actions_t
* file_actions, int from);
int
posix_spawn_file_actions_addchdir_np
(posix_spawn_file_actions_t
*restrict file_actions, const char *restrict
path);
int
posix_spawn_file_actions_addfchdir_np
(posix_spawn_file_actions_t
* file_actions, int fildes);
DESCRIPTION
These functions add an open, dup2 or close action to a spawn file actions object.
A spawn file actions object is of type
posix_spawn_file_actions_t (defined in
<spawn.h>
) and is used to
specify a series of actions to be performed by a
posix_spawn
()
or
posix_spawnp
()
operation in order to arrive at the set of open file descriptors for the
child process given the set of open file descriptors of the parent.
A spawn file actions object, when passed to
posix_spawn
()
or
posix_spawnp
(),
specify how the set of open file descriptors in the calling process is
transformed into a set of potentially open file descriptors for the spawned
process. This transformation is as if the specified sequence of actions was
performed exactly once, in the context of the spawned process (prior to
execution of the new process image), in the order in which the actions were
added to the object; additionally, when the new process image is executed,
any file descriptor (from this new set) which has its
FD_CLOEXEC
flag set is closed (see
posix_spawn
()).
The
posix_spawn_file_actions_addopen
()
function adds an open action to the object referenced by
file_actions that causes the file named by
path to be opened (as if
open(path, oflag, mode)
had been called, and the returned file descriptor, if not fildes, had been changed to fildes) when a new process is spawned using this file actions object. If fildes was already an open file descriptor, it is closed before the new file is opened.
The string described by
path is copied by the
posix_spawn_file_actions_addopen
()
function.
The
posix_spawn_file_actions_adddup2
()
function adds a dup2 action to the object referenced by
file_actions that causes the file descriptor
fildes to be duplicated as
newfildes (as if
dup2(fildes, newfildes)
had been called) when a new process is spawned using
this file actions object, except that the FD_CLOEXEC
flag for newfildes is cleared even if
fildes is equal to newfildes.
The difference from
dup2
() is
useful for passing a particular file descriptor to a particular child
process.
The
posix_spawn_file_actions_addclose
()
function adds a close action to the object referenced by
file_actions that causes the file descriptor
fildes to be closed (as if
close(fildes)
had been called) when a new process is spawned using this file actions object.
The
posix_spawn_file_actions_addclosefrom_np
()
function adds a close action to close all file descriptors numerically equal
or greater then the argument from. For each open file
descriptor, logically the close action is performed, and any possible errors
encountered are ignored.
The
posix_spawn_file_actions_addchdir_np
()
and
posix_spawn_file_actions_addfchdir_np
()
functions add a change current directory action to the object referenced by
file_actions that affects actions (opens with relative
path) performed after the operation, in the order of insertion into the
file_actions object. It also sets the working
directory for the spawned program. The
posix_spawn_file_actions_addchdir_np
() function
takes the path to set as the working directory, while
posix_spawn_file_actions_addfchdir_np
() takes the
directory file descriptor.
RETURN VALUES
Upon successful completion, these functions return zero; otherwise, an error number is returned to indicate the error.
ERRORS
These functions fail if:
- [
EBADF
] - The value specified by fildes or newfildes is negative.
- [
ENOMEM
] - Insufficient memory exists to add to the spawn file actions object.
SEE ALSO
close(2), dup2(2), open(2), posix_spawn(3), posix_spawn_file_actions_destroy(3), posix_spawn_file_actions_init(3), posix_spawnp(3)
STANDARDS
The posix_spawn_file_actions_addopen
(),
posix_spawn_file_actions_adddup2
() and
posix_spawn_file_actions_addclose
() functions
conform to IEEE Std 1003.1-2001
(“POSIX.1”), with the exception of the behavior of
posix_spawn_file_actions_adddup2
() if
fildes is equal to newfildes
(clearing FD_CLOEXEC
). A future update of the
Standard is expected to require this behavior.
The
posix_spawn_file_actions_addchdir_np
(),
posix_spawn_file_actions_addfchdir_np
(), and
posix_spawn_file_actions_addclosefrom_np
() functions
are non-standard functions implemented after the similar functionality
provided by glibc.
HISTORY
The posix_spawn_file_actions_addopen
(),
posix_spawn_file_actions_adddup2
() and
posix_spawn_file_actions_addclose
() functions first
appeared in FreeBSD 8.0. The
posix_spawn_file_actions_addchdir_np
(),
posix_spawn_file_actions_addfchdir_np
(), and
posix_spawn_file_actions_addclosefrom_np
() functions
first appeared in FreeBSD 13.1.
AUTHORS
Ed Schouten <ed@FreeBSD.org>