sigismember - Man Page

test for a signal in a signal set


This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.


#include <signal.h>

int sigismember(const sigset_t *set, int signo);


The sigismember() function shall test whether the signal specified by signo is a member of the set pointed to by set.

Applications should call either sigemptyset() or sigfillset() at least once 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 pthread_sigmask(), sigaction(), sigaddset(), sigdelset(), sigismember(), sigpending(), sigprocmask(), sigsuspend(), sigtimedwait(), sigwait(), or sigwaitinfo(), the results are undefined.

Return Value

Upon successful completion, sigismember() shall return 1 if the specified signal is a member of the specified set, or 0 if it is not. Otherwise, it shall return -1 and set errno to indicate the error.


The sigismember() function may fail if:


The signo argument is not a valid signal number, or is an unsupported signal number.

The following sections are informative.



Application Usage




Future Directions


See Also

Section 2.4, Signal Concepts, pthread_sigmask(), sigaction(), sigaddset(), sigdelset(), sigfillset(), sigemptyset(), sigpending(), sigsuspend()

The Base Definitions volume of POSIX.1-2017, <signal.h>

Referenced By

pthread_sigmask(3p), sigaction(3p), sigaddset(3p), sigdelset(3p), sigemptyset(3p), sigfillset(3p), signal.h(0p), sigpending(3p).

2017 IEEE/The Open Group POSIX Programmer's Manual