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POSIX defines the sigaction(2) function, which assigns handlers to signals like signal(2), but also allows one to explicitly set persistence. One can thus use sigaction(2) and sidestep the race window on non-persistent OS's.

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

In fact, POSIX recommends sigaction(2) and deprecates signal(2). Unfortunately, sigaction(2) is not C99-compliant.

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POSIX defines the sigaction(2) function, which assigns handlers to signals like signal(2), but also allows one to explicitly set persistence. One can thus use sigaction(2) and sidestep the race window on non-persistent OS's.

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

In fact, POSIX recommends sigaction(2) and deprecates signal(2). Unfortunately, sigaction(2) is not C99-compliant.

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