sigqueue — queue a signal and data to a process
#include <signal.h>
int
sigqueue( |
pid_t | pid, |
int | sig, | |
const union sigval | value) ; |
sigqueue
() sends the signal
specified in sig
to
the process whose PID is given in pid
. The permissions required
to send a signal are the same as for kill(2). As with kill(2), the null signal
(0) can be used to check if a process with a given PID
exists.
The value
argument
is used to specify an accompanying item of data (either an
integer or a pointer value) to be sent with the signal, and
has the following type:
union sigval { int sival_int; void *sival_ptr; };
If the receiving process has installed a handler for this
signal using the SA_SIGINFO
flag to sigaction(2), then it can
obtain this data via the si_value
field of the
siginfo_t
structure
passed as the second argument to the handler. Furthermore,
the si_code
field
of that structure will be set to SI_QUEUE
.
On success, sigqueue
()
returns 0, indicating that the signal was successfully queued
to the receiving process. Otherwise −1 is returned and
errno
is set to indicate the
error.
The limit of signals which may be queued has been reached. (See signal(7) for further information.)
sig
was
invalid.
The process does not have permission to send the signal to the receiving process. For the required permissions, see kill(2).
No process has a PID matching pid
.
If this function results in the sending of a signal to the process that invoked it, and that signal was not blocked by the calling thread, and no other threads were willing to handle this signal (either by having it unblocked, or by waiting for it using sigwait(3)), then at least some signal must be delivered to this thread before this function returns.
kill(2), sigaction(2), signal(2), sigwait(3), signal(7)
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