sigismember - test for member of signal set

Syntax	#include <signal.h> int sigismember(const sigset_t *set, int sig);
Description	sigismember() tests whether the signal sig is a member of the set pointed to by set.
Return val.	1	upon successful completion, if the specified signal is a member of the specified set.
	0	upon successful completion, if the specified signal is not contained in the specified set.
	-1	if an error occurs. errno is set to indicate the error.
Errors	sigismember() will fail if:
	EINVAL	The value of sig is an invalid or unsupported signal number.
Notes	Applications should call sigemptyset() or sigfillset() for each object of type sigset_t prior to any other use of that object. If such an object is not initialized in this way, but is nonetheless supplied as an argument to any of sigaction(), sigaddset(), sigdelset(), sigismember(), sigpending() or sigprocmask(), the behavior is undefined.
See also	sigdelset(), sigemptyset(), sigfillset(), sigismember(), signal.h.