// The nohup program seems to let things kill its kids in fedora 20.
// This program will endeavor to eradicate whatever is leaking through
// nohup.

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>
#include <string.h>

int bastards[] = {
   SIGHUP, SIGINT, SIGQUIT, SIGABRT, SIGFPE, SIGPIPE, SIGTERM,
   SIGUSR1, SIGUSR2
};

#ifdef DO_DEBUG

#define DBPRINTF(args) \
   { \
      FILE * dbf = fopen("/home/tom/dammit.log", "a"); \
      fprintf args; \
      fclose(dbf); \
   }

#else

#define DBPRINTF(args)

#endif

int
main(int argc, char ** argv) {

   // Make everything point to /dev/null, close all other file descriptors

   int null_out_fd = open("/dev/null", O_WRONLY);
   int null_in_fd = open("/dev/null", O_RDONLY);
   dup2(null_out_fd, fileno(stdout));
   dup2(null_out_fd, fileno(stderr));
   dup2(null_in_fd, fileno(stdin));
   for (int i = 3; i < 60000; ++i) {
      close(i);
   }

   // Ignore every ignorable signal

   struct sigaction act;
   for (int i = 0; i < sizeof(bastards)/sizeof(bastards[0]); ++i) {
      memset((void *)&act, 0, sizeof(act));
      act.sa_handler = SIG_IGN;
      sigaction(bastards[i], &act, NULL);
   }

   // Fork a child we can make into a new session

   pid_t kid = fork();
   if (kid == 0) {
      // This is the child. Make a new session here.
      pid_t s = setsid();
      DBPRINTF((dbf,"1st setsid call returns %d\n",(int)s))
      // Now fork yet another child to do all the real work and make
      // the intermediate child exit.
      pid_t grandkid = fork();
      if (grandkid == 0) {
         s = setsid(); // Just to make doubly sure.
         DBPRINTF((dbf,"2nd setsid call returns %d\n",(int)s))
         ++argv;
         --argc;
         execvp(argv[0], argv);
         DBPRINTF((dbf,"Oops. Executed past the exec of %s\n",argv[0]))
         _exit(2);
      } else {
         _exit(0);
      }
   } else {
      // This is the parent, wait for the kid.
      int status;
      waitpid(kid, &status, 0);
   }
   return 0;
}