Manual Pages  — POSIX_SPAWN_FILE_ACTIONS_ADDOPEN

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 SYNOPSIS DESCRIPTION RETURN VALUES ERRORS SEE ALSO STANDARDS HISTORY AUTHORS

Standard C Library (libc, -lc)

#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);

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.

Upon successful completion, these functions return zero; otherwise, an error number is returned to indicate the error.

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.

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_addopen(), posix_spawn_file_actions_adddup2() and posix_spawn_file_actions_addclose() functions first appeared in FreeBSD 8.0 .

amp;Ed Schouten <Mt ed@FreeBSD.org>