SIGSETMASK(3) | 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.

December 13, 2022 | Debian