fusl/src/legacy/daemon.c

#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>

int daemon(int nochdir, int noclose) {
  if (!nochdir && chdir("/"))
    return -1;
  if (!noclose) {
    int fd, failed = 0;
    if ((fd = open("/dev/null", O_RDWR)) < 0)
      return -1;
    if (dup2(fd, 0) < 0 || dup2(fd, 1) < 0 || dup2(fd, 2) < 0)
      failed++;
    if (fd > 2)
      close(fd);
    if (failed)
      return -1;
  }

  switch (fork()) {
    case 0:
      break;
    case -1:
      return -1;
    default:
      _exit(0);
  }

  if (setsid() < 0)
    return -1;

  switch (fork()) {
    case 0:
      break;
    case -1:
      return -1;
    default:
      _exit(0);
  }

  return 0;
}