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download PDF document: posix_spawn_file_actions_adddup2.3.pdf

POSIX_SPAWN_FILE_ACTIONS_ADDOPEN(3) FreeBSD Library Functions Manual
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()). 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_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 14.0.
AUTHORS Ed Schouten <ed@FreeBSD.org>
FreeBSD 14.0-RELEASE-p11 May 9, 2013 FreeBSD 14.0-RELEASE-p11