NAME
sigtimedwait,
sigwaitinfo —
wait for queued signals
(REALTIME)
LIBRARY
library “libc”
SYNOPSIS
#include
<signal.h>
int
sigtimedwait(const sigset_t *restrict
set, siginfo_t *restrict info,
const struct timespec *restrict timeout);
int
sigwaitinfo(const
sigset_t * restrict set,
siginfo_t * restrict
info);
DESCRIPTION
Thesigtimedwait()
system call is equivalent to sigwaitinfo() except that
if none of the signals specified by set are pending,
sigtimedwait() waits for the time interval specified
in the timespec structure referenced by
timeout. If the timespec structure
pointed to by timeout is zero-valued and if none of the
signals specified by set are pending, then
sigtimedwait() returns immediately with an error. If
timeout is the NULL pointer, the
behavior is unspecified. CLOCK_MONOTONIC clock is used
to measure the time interval specified by the timeout
argument.
The
sigwaitinfo()
system call selects the pending signal from the set specified by
set. Should any of multiple pending signals in the
range SIGRTMIN to SIGRTMAX
be selected, it shall be the lowest numbered one. The selection order
between realtime and non-realtime signals, or between multiple pending
non-realtime signals, is unspecified. If no signal in
set is pending at the time of the call, the calling
thread is suspended until one or more signals in set
become pending or until it is interrupted by an unblocked, caught
signal.
The
sigwaitinfo()
system call is equivalent to the
sigwait()
system call if the info argument is
NULL. If the info argument is
non-NULL, the sigwaitinfo()
function is equivalent to sigwait(), except that the
selected signal number shall be stored in the si_signo
member, and the cause of the signal shall be stored in the
si_code member. Besides this, the
sigwaitinfo() and
sigtimedwait() system calls may return
EINTR if interrupted by signal, which is not allowed
for the sigwait() function.
If any value is queued to the selected signal, the first such
queued value is dequeued and, if the info argument is
non-NULL, the value is stored in the
si_value member of info. The
system resource used to queue the signal is released and returned to the
system for other use. If no value is queued, the content of the
si_value member is zero-valued. If no further signals
are queued for the selected signal, the pending indication for that signal
is reset.
RETURN VALUES
Upon successful completion (that is, one of the signals specified
by set is pending or is generated)
sigwaitinfo() and
sigtimedwait() return the selected signal number.
Otherwise, the functions return a value of -1 and set the global variable
errno to indicate the error.
ERRORS
The sigtimedwait() system call will fail
if:
- [
EAGAIN] - No signal specified by set was generated within the specified timeout period.
The sigtimedwait() and
sigwaitinfo() system calls fail if:
- [
EINTR] - The wait was interrupted by an unblocked, caught signal.
The sigtimedwait() system call may also
fail if:
- [
EINVAL] - The timeout argument specified a tv_nsec value less than zero or greater than or equal to 1000 million. Kernel only checks for this error if no signal is pending in set and it is necessary to wait.
SEE ALSO
sigaction(2), sigpending(2), sigqueue(2), sigsuspend(2), sigwait(2), pause(3), pthread_sigmask(3), siginfo(3)
STANDARDS
The sigtimedwait() and
sigwaitinfo() system calls conform to
ISO/IEC 9945-1:1996 (“POSIX.1”).