release/src/router/busybox/miscutils/setsid.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * setsid.c -- execute a command in a new session
   4  * Rick Sladkey <jrs@world.std.com>
   5  * In the public domain.
   6  *
   7  * 1999-02-22 Arkadiusz Mickiewicz <misiek@pld.ORG.PL>
   8  * - added Native Language Support
   9  *
  10  * 2001-01-18 John Fremlin <vii@penguinpowered.com>
  11  * - fork in case we are process group leader
  12  *
  13  * 2004-11-12 Paul Fox
  14  * - busyboxed
  15  */
  16
  17 //usage:#define setsid_trivial_usage
  18 //usage:       "PROG ARGS"
  19 //usage:#define setsid_full_usage "\n\n"
  20 //usage:       "Run PROG in a new session. PROG will have no controlling terminal\n"
  21 //usage:       "and will not be affected by keyboard signals (Ctrl-C etc).\n"
  22 //usage:       "See setsid(2) for details."
  23
  24 #include "libbb.h"
  25
  26 int setsid_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  27 int setsid_main(int argc UNUSED_PARAM, char **argv)
  28 {
  29         if (!argv[1])
  30                 bb_show_usage();
  31
  32         /* setsid() is allowed only when we are not a process group leader.
  33          * Otherwise our PID serves as PGID of some existing process group
  34          * and cannot be used as PGID of a new process group. */
  35         if (setsid() < 0) {
  36                 pid_t pid = fork_or_rexec(argv);
  37                 if (pid != 0) {
  38                         /* parent */
  39                         /* TODO:
  40                          * we can waitpid(pid, &status, 0) and then even
  41                          * emulate exitcode, making the behavior consistent
  42                          * in both forked and non forked cases.
  43                          * However, the code is larger and upstream
  44                          * does not do such trick.
  45                          */
  46                         exit(EXIT_SUCCESS);
  47                 }
  48
  49                 /* child */
  50                 /* now there should be no error: */
  51                 setsid();
  52         }
  53
  54         argv++;
  55         BB_EXECVP_or_die(argv);
  56 }