SIGWAITINFO(3C)SIGWAITINFO(3C)NAME
sigwaitinfo, sigtimedwait - wait for queued signals
SYNOPSIS
#include <signal.h>
int sigwaitinfo(const sigset_t *restrict set,
siginfo_t *restrict info);
int sigtimedwait(const sigset_t *restrict set,
siginfo_t *restrict info,
const struct timespec *restrict timeout);
DESCRIPTION
The sigwaitinfo() function 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 will 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() function behaves the same as the sigwait(2) function
if the info argument is NULL. If the info argument is non-NULL, the
sigwaitinfo() function behaves the same as sigwait(2), except that the
selected signal number is stored in the si_signo member, and the cause
of the signal is stored in the si_code member. 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 mem‐
ber of info. The system resource used to queue the signal will be
released and made available to queue other signals. If no value is
queued, the content of the si_value member is undefined. If no further
signals are queued for the selected signal, the pending indication for
that signal will be reset. If the value of the si_code member is
SI_NOINFO, only the si_signo member of siginfo_t is meaningful, and the
value of all other members is unspecified.
The sigtimedwait() function behaves the same as sigwaitinfo() except
that if none of the signals specified by set are pending, sigtimed‐
wait() 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.
If, while sigwaitinfo() or sigtimedwait() is waiting, a signal occurs
which is eligible for delivery (that is, not blocked by the process
signal mask), that signal is handled asynchronously and the wait is
interrupted.
RETURN VALUES
Upon successful completion (that is, one of the signals specified by
set is pending or is generated) sigwaitinfo() and sigtimedwait() will
return the selected signal number. Otherwise, the function returns −1
and sets errno to indicate the error.
ERRORS
The sigwaitinfo() and sigtimedwait() functions will fail if:
EINTR
The wait was interrupted by an unblocked, caught signal.
ENOSYS
The sigwaitinfo() and sigtimedwait() functions are not sup‐
ported.
The sigtimedwait() function will fail if:
EAGAIN
No signal specified by set was generated within the specified
timeout period.
The sigwaitinfo() and sigtimedwait() functions may fail if:
EFAULT
The set, info, or timeout argument points to an invalid
address.
The sigtimedwait() function may fail if:
EINVAL
The timeout argument specified a tv_nsec value less than zero
or greater than or equal to 1000 million. The system only
checks for this error if no signal is pending in set and it
is necessary to wait.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬───────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼───────────────────┤
│Interface Stability │ Committed │
├────────────────────┼───────────────────┤
│MT-Level │ Async-Safe │
├────────────────────┼───────────────────┤
│Standard │ See standards(5). │
└────────────────────┴───────────────────┘
SEE ALSOtime(2), sigqueue(3C), siginfo.h(3HEAD), signal.h(3HEAD),
time.h(3HEAD), attributes(5), standards(5)
Feb 5, 2008 SIGWAITINFO(3C)
