sigemptyset() — Initialize a signal mask to exclude all signals

Standards

Standards / Extensions	C or C++	Dependencies
POSIX.1 XPG4 XPG4.2 Single UNIX Specification, Version 3	both

Format

#define _POSIX_SOURCE
#include <signal.h>

int sigemptyset(sigset_t *set);

General description

Initializes a signal set set to the empty set. All recognized signals are excluded.

sigemptyset() is part of a family of functions that manipulate signal sets. Signal sets are data objects that let a process keep track of groups of signals. For example, a process can create one signal set to record which signals it is blocking, and another signal set to record which signals are pending. Signal sets are used to manipulate groups of signals used by other functions (such as sigprocmask()) or to examine signal sets returned by other functions (such as sigpending()).

Returned value

If successful, sigemptyset() returns 0.

There are no documented errno values.

Example

CELEBS17

/* CELEBS17

   This example initializes a set of signals to an empty set.

 */
#define _POSIX_SOURCE
#include <stdio.h>
#include <signal.h>
#include <unistd.h>

main() {
  struct sigaction sact;

  sigemptyset(&sact.sa_mask);
  sact.sa_flags = 0;
  sact.sa_handler = SIG_IGN;

  sigaction(SIGUSR2, &sact, NULL);

  puts("before kill()");
  kill(getpid(), SIGUSR2);
  puts("after kill()");
}

Output

before kill()
after kill()