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SIGSETMASK(3) FreeBSD Library Functions Manual SIGSETMASK(3) NAME sigsetmask - set current signal mask SYNOPSIS #include <signal.h> int sigsetmask(int mask); DESCRIPTION This interface is made obsolete by sigprocmask(2). sigsetmask() sets the current signal mask. Signals are blocked from delivery if the corresponding bit in mask is a 1; the macro sigmask(3) is provided to construct the mask for a given signum. The system quietly disallows SIGKILL or SIGSTOP to be blocked. RETURN VALUES The previous set of masked signals is returned. EXAMPLES The following example utilizing sigsetmask(): int omask; omask = sigblock(sigmask(SIGINT) | sigmask(SIGHUP)); ... sigsetmask(omask & ~(sigmask(SIGINT) | sigmask(SIGHUP))); Could be converted literally to: sigset_t set, oset; sigemptyset(&set); sigaddset(&set, SIGINT); sigaddset(&set, SIGHUP); sigprocmask(SIG_BLOCK, &set, &oset); ... sigdelset(&oset, SIGINT); sigdelset(&oset, SIGHUP); sigprocmask(SIG_SETMASK, &oset, NULL); Another, clearer, alternative is: sigset_t set; sigemptyset(&set); sigaddset(&set, SIGINT); sigaddset(&set, SIGHUP); sigprocmask(SIG_BLOCK, &set, NULL); ... sigprocmask(SIG_UNBLOCK, &set, NULL); To completely clear the signal mask using sigsetmask() one can do: (void) sigsetmask(0); Which can be expressed via sigprocmask(2) as: sigset_t eset; sigemptyset(&eset); (void) sigprocmask(SIG_SETMASK, &eset, NULL); SEE ALSO kill(2), sigaction(2), sigprocmask(2), sigsuspend(2), sigaddset(3), sigblock(3), sigvec(3) HISTORY A sigsetmask() system call first appeared in 4.2BSD. In 4.3BSD-Reno, it was reimplemented as a wrapper around sigprocmask(2). The old system call was kept for compatibility until OpenBSD 4.9. FreeBSD 14.1-RELEASE-p8 December 13, 2022 FreeBSD 14.1-RELEASE-p8