SIGSETMASK(3)

NAME
sigsetmask - set current signal mask

SYNOPSIS
#include <signal.h>
int
sigsetmask(int mask);
sigmask(int signum);

DESCRIPTION
This interface is made obsoleted 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() 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), sigblock(3), sigsetops(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.