#include <signal.h> int
sigwait (const sigset_t * restrict set int * restrict sig);
system call selects a set of signals, specified by
Fa set .
If none of the selected signals are pending,
waits until one or more of the selected signals has been generated.
atomically clears one of the selected signals from the set of pending signals
for the process and sets the location pointed to by
to the signal number that was cleared.
The signals specified by
should be blocked at the time of the call to
If more than one thread is using
to wait for the same signal, no more than one of these threads will return from
with the signal number.
If more than a single thread is blocked in
for a signal when that signal is generated for the process, it is unspecified
which of the waiting threads returns from
If the signal is generated for a specific thread, as by
only that thread will return.
Should any of the multiple pending signals in the range
selected, it will be the lowest numbered one.
The selection order between realtime
and non-realtime signals, or between multiple pending non-realtime signals,
returns 0 and sets the location pointed to by
to the cleared signal number.
Otherwise, an error number is returned.
system call will fail if:
Bq Er EINVAL
specifies one or more invalid signal numbers.
Bq Er EFAULT
Any arguments point outside the allocated address space or there is a
memory protection fault.