NAME
sigwait —
select a set of signals
LIBRARY
library “libc”
SYNOPSIS
#include
<signal.h>
int
sigwait(const
sigset_t * restrict set,
int * restrict sig);
DESCRIPTION
Thesigwait()
system call selects a set of signals, specified by set.
If none of the selected signals are pending, sigwait()
waits until one or more of the selected signals has been generated. Then
sigwait() atomically clears one of the selected
signals from the set of pending signals (for the process or for the current
thread) and sets the location pointed to by sig to the
signal number that was cleared.
The signals specified by set
should be blocked at the time of the call to
sigwait().
If more than one thread is using
sigwait()
to wait for the same signal, no more than one of these threads will return
from sigwait() with the signal number. If more than
a single thread is blocked in sigwait() for a signal
when that signal is generated for the process, it is unspecified which of
the waiting threads returns from sigwait(). If the
signal is generated for a specific thread, as by
pthread_kill(),
only that thread will return.
Should any of the 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.
IMPLEMENTATION NOTES
The sigwait() function is implemented as a
wrapper around the __sys_sigwait() system call,
which retries the call on EINTR error.
RETURN VALUES
If successful, sigwait() returns 0 and
sets the location pointed to by sig to the cleared
signal number. Otherwise, an error number is returned.
ERRORS
The sigwait() system call will fail
if:
- [
EINVAL] - The set argument specifies one or more invalid signal numbers.
SEE ALSO
sigaction(2), sigpending(2), sigqueue(2), sigsuspend(2), sigtimedwait(2), sigwaitinfo(2), pause(3), pthread_sigmask(3)
STANDARDS
The sigwait() function conforms to
ISO/IEC 9945-1:1996 (“POSIX.1”).