13.6.c

#include <pthread.h>
#include <syslog.h>
#include "apue.h"

sigset_t mask;

extern int already_running(void);

void reread(void) {}

void *thr_fn(void *arg) {
  int err, signo;

  for (;;) {
    err = sigwait(&mask, &signo);
    if (err != 0) {
      syslog(LOG_ERR, "sigwait failed");
      exit(1);
    }
    switch (signo) {
      case SIGHUP:
        syslog(LOG_INFO, "Re-reading configuration file");
        reread();
        break;
      case SIGTERM:
        syslog(LOG_INFO, "got SIGTERM; exiting");
        exit(0);
      default:
        syslog(LOG_INFO, "unexpected signal %d\n", signo);
    }
  }
  return (0);
}

int main(int argc, char *argv[]) {
  int err;
  pthread_t tid;
  char *cmd;
  struct sigaction sa;

  if ((cmd = strrchr(argv[0], '/')) == NULL) {
    cmd = argv[0];
  } else {
    cmd++;
  }

  daemonize(cmd);

  if (already_running()) {
    syslog(LOG_ERR, "daemon already running");
    exit(1);
  }

  sa.sa_handler = SIG_DFL;
  sigemptyset(&sa.sa_mask);
  sa.sa_flags = 0;
  if (sigaction(SIGHUP, &sa, NULL) < 0) {
    err_quit("%s: can't restore SIGHUP default");
  }
  sigfillset(&mask);
  if ((err = pthread_sigmask(SIG_BLOCK, &mask, NULL)) != 0) {
    err_exit(err, "SIG_BLOCK error");
  }

  err = pthread_create(&tid, NULL, thr_fn, 0);
  if (err != 0) {
    err_exit(err, "can't create thread");
  }

  exit(0);
}