NAME
posix_spawn_file_actions_addopen,
posix_spawn_file_actions_adddup2,
posix_spawn_file_actions_addclose —
add open, dup2 or close action to spawn
file actions object
LIBRARY
library “libc”
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);
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.
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.
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.
AUTHORS
Ed Schouten <ed@FreeBSD.org>