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/* Equivalent to signal(SIGUSR1, handler) but makemakes
 * signal persistent */
struct sigaction act;
act.sa_handler = handler;
act.sa_flags = 0;
if (sigemptyset(&act.sa_mask) != 0) {
  /* handle error */
}
if (sigaction(SIGUSR1, &act, NULL) != 0) {
  /* handle error */
}

/* Equivalent to signal(SIGUSR1, handler) but makemakes
 * signal non-persistent */
struct sigaction act;
act.sa_handler = handler;
act.sa_flags = SA_RESETHAND;
if (sigemptyset(&act.sa_mask) != 0) {
  /* handle error */
}
if (sigaction(SIGUSR1, &act, NULL) != 0) {
  /* handle error */
}