NAME
posix_spawn_file_actions_adddup2 —
add dup2 action to spawn file actions object (ADVANCED
REALTIME)
SYNOPSIS
int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t
*file_actions, int fildes, int newfildes);
DESCRIPTION
The posix_spawn_file_actions_adddup2 ()
function shall add a dup2(3) action to the object
referenced by
file_actions
that shall cause 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.
A spawn file actions object is as defined in posix_spawn_file_actions_addclose(3).
RETURN VALUE
Upon successful completion, the
posix_spawn_file_actions_adddup2 () function shall
return zero; otherwise, an error number shall be returned to indicate the
error.
ERRORS
The posix_spawn_file_actions_adddup2 ()
function shall fail if:
- [EBADF]
- The value specified by fildes or newfildes is negative or greater than or equal to {OPEN_MAX}.
- [ENOMEM]
- Insufficient memory exists to add to the spawn file actions object.
The posix_spawn_file_actions_adddup2 ()
function may fail if:
- [EINVAL]
- The value specified by file_actions is invalid.
It shall not be considered an error for the
fildes argument passed to the
posix_spawn_file_actions_adddup2 () function to
specify a file descriptor for which the specified operation could not be
performed at the time of the call. Any such error will be detected when the
associated file actions object is later used during a
posix_spawn(3) or posix_spawnp(3)
operation.
EXAMPLES
None.
APPLICATION USAGE
The posix_spawn_file_actions_adddup2 ()
function is part of the Spawn option and need not be provided on all
implementations.
Implementations may use file descriptors that must be
inherited into child processes for the child process to remain conforming,
such as for message catalog or tracing purposes. Therefore, an application
that calls posix_spawn_file_actions_adddup2 () with
an arbitrary integer for newfildes risks non-conforming
behavior, and this function can only portably be used to overwrite file
descriptor values that the application has obtained through explicit
actions, or for the three file descriptors corresponding to the standard
file streams. In order to avoid a race condition of leaking an unintended
file descriptor into a child process, an application should consider opening
all file descriptors with the FD_CLOEXEC bit set unless the file descriptor
is intended to be inherited across
exec.
RATIONALE
Refer to the RATIONALE section in posix_spawn_file_actions_addclose(3).
FUTURE DIRECTIONS
None.
SEE ALSO
dup(3), posix_spawn(3), posix_spawn_file_actions_addclose(3), posix_spawn_file_actions_destroy(3)
XBD <spawn.h>
CHANGE HISTORY
First released in Issue 6. Derived from IEEE Std 1003.1d-1999.
IEEE PASC Interpretation 1003.1 #104 is applied, noting that the [EBADF] error can apply to the newfildes argument in addition to fildes.
Issue 7
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0440 [149] is applied.