sigwait¶
Synopsis¶
#include <signal.h>
int sigwait(const sigset_t *restrict set, int *restrict sig);
Status¶
Implemented
Conformance¶
IEEE Std 1003.1-2017
Description¶
The sigwait() function shall select a pending signal from set, atomically clear it from the system’s set of pending
signals, and return that signal number in the location referenced by sig. If prior to the call to sigwait() there
are multiple pending instances of a single signal number, it is implementation-defined whether upon successful return
there are any remaining pending signals for that signal number. Signals are not queued, so multiple pending instances
of a signal number are kept as one pending signal, which is cleared by sigwait(). If no signal in set is pending at
the time of the call, the thread shall be suspended until one or more becomes pending. The signals defined by set
shall have been blocked at the time of the call to sigwait(); otherwise, the behavior is undefined. The effect of
sigwait() on the signal actions for the signals in set is unspecified.
If more than one thread is using sigwait() to wait for the same signal, no more than one of these threads shall
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 shall return.
The selection order between multiple pending signals is unspecified. Realtime signals (SIGRTMIN to SIGRTMAX) are not
supported.
A signal caught by a signal-catching function while the thread waits in sigwait() doesn’t end the wait: sigwait()
continues to wait for a signal from set.
Return value¶
Upon successful completion, sigwait() shall store the signal number of the received signal at the location referenced
by sig and return zero. Otherwise, an error number shall be returned to indicate the error.
Errors¶
The sigwait() function may fail if:
EINVAL- The set argument contains an invalid or unsupported signal number.
POSIX deviations¶
No POSIX deviations discovered.