1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * setsid.c -- execute a command in a new session
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4 | * Rick Sladkey <jrs@world.std.com>
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5 | * In the public domain.
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6 | *
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7 | * 1999-02-22 Arkadiusz Mickiewicz <misiek@pld.ORG.PL>
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8 | * - added Native Language Support
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9 | *
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10 | * 2001-01-18 John Fremlin <vii@penguinpowered.com>
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11 | * - fork in case we are process group leader
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12 | *
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13 | * 2004-11-12 Paul Fox
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14 | * - busyboxed
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15 | */
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16 |
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17 | //usage:#define setsid_trivial_usage
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18 | //usage: "[-c] PROG ARGS"
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19 | //usage:#define setsid_full_usage "\n\n"
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20 | //usage: "Run PROG in a new session. PROG will have no controlling terminal\n"
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21 | //usage: "and will not be affected by keyboard signals (^C etc).\n"
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22 | //usage: "\n -c Set controlling terminal to stdin"
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23 |
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24 | #include "libbb.h"
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25 |
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26 | int setsid_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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27 | int setsid_main(int argc UNUSED_PARAM, char **argv)
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28 | {
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29 | unsigned opt;
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30 |
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31 | opt_complementary = "-1"; /* at least one arg */
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32 | opt = getopt32(argv, "+c"); /* +: stop on first non-opt */
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33 | argv += optind;
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34 |
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35 | /* setsid() is allowed only when we are not a process group leader.
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36 | * Otherwise our PID serves as PGID of some existing process group
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37 | * and cannot be used as PGID of a new process group.
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38 | *
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39 | * Example: setsid() below fails when run alone in interactive shell:
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40 | * $ setsid PROG
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41 | * because shell's child (setsid) is put in a new process group.
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42 | * But doesn't fail if shell is not interactive
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43 | * (and therefore doesn't create process groups for pipes),
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44 | * or if setsid is not the first process in the process group:
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45 | * $ true | setsid PROG
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46 | * or if setsid is executed in backquotes (`setsid PROG`)...
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47 | */
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48 | if (setsid() < 0) {
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49 | pid_t pid = fork_or_rexec(argv);
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50 | if (pid != 0) {
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51 | /* parent */
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52 | /* TODO:
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53 | * we can waitpid(pid, &status, 0) and then even
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54 | * emulate exitcode, making the behavior consistent
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55 | * in both forked and non forked cases.
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56 | * However, the code is larger and upstream
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57 | * does not do such trick.
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58 | */
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59 | return EXIT_SUCCESS;
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60 | }
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61 |
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62 | /* child */
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63 | /* now there should be no error: */
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64 | setsid();
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65 | }
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66 |
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67 | if (opt) {
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68 | /* -c: set (with stealing) controlling tty */
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69 | ioctl(0, TIOCSCTTY, 1);
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70 | }
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71 |
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72 | BB_EXECVP_or_die(argv);
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73 | }
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