sigprocmask()

Purpose

sigprocmask() changes the calling thread's signal mask.

It is commonly used before signalfd() so selected signals are delivered through a file descriptor instead of traditional handlers.

Header

#include <signal.h>

Prototype

int sigprocmask(int how, const sigset_t *set, sigset_t *oldset);

Minimal Example

sigset_t mask;

sigemptyset(&mask);
sigaddset(&mask, SIGINT);
sigaddset(&mask, SIGTERM);

if (sigprocmask(SIG_BLOCK, &mask, NULL) < 0) {
    perror("sigprocmask");
    return -1;
}

Common Pitfalls

• Creating a signalfd without blocking the same signals first.
• Blocking signals globally without documenting shutdown behavior.
• Confusing process signal disposition with per-thread signal masks.

Related Topics

• Event Loop
• Network Programming
• IPC