blob: 637081b6ccdad0b03212f51235f99bdea116f123
| 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 | * |
| 36 | * Example: setsid() below fails when run alone in interactive shell: |
| 37 | * $ setsid PROG |
| 38 | * because shell's child (setsid) is put in a new process group. |
| 39 | * But doesn't fail if shell is not interactive |
| 40 | * (and therefore doesn't create process groups for pipes), |
| 41 | * or if setsid is not the first process in the process group: |
| 42 | * $ true | setsid PROG |
| 43 | * or if setsid is executed in backquotes (`setsid PROG`)... |
| 44 | */ |
| 45 | if (setsid() < 0) { |
| 46 | pid_t pid = fork_or_rexec(argv); |
| 47 | if (pid != 0) { |
| 48 | /* parent */ |
| 49 | /* TODO: |
| 50 | * we can waitpid(pid, &status, 0) and then even |
| 51 | * emulate exitcode, making the behavior consistent |
| 52 | * in both forked and non forked cases. |
| 53 | * However, the code is larger and upstream |
| 54 | * does not do such trick. |
| 55 | */ |
| 56 | return EXIT_SUCCESS; |
| 57 | } |
| 58 | |
| 59 | /* child */ |
| 60 | /* now there should be no error: */ |
| 61 | setsid(); |
| 62 | } |
| 63 | |
| 64 | argv++; |
| 65 | BB_EXECVP_or_die(argv); |
| 66 | } |
| 67 |