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//config:config SETSID 17//config: bool "setsid (3.6 kb)" 18//config: default y 19//config: help 20//config: setsid runs a program in a new session 21 22//applet:IF_SETSID(APPLET(setsid, BB_DIR_USR_BIN, BB_SUID_DROP)) 23 24//kbuild:lib-$(CONFIG_SETSID) += setsid.o 25 26//usage:#define setsid_trivial_usage 27//usage: "[-c] PROG ARGS" 28//usage:#define setsid_full_usage "\n\n" 29//usage: "Run PROG in a new session. PROG will have no controlling terminal\n" 30//usage: "and will not be affected by keyboard signals (^C etc).\n" 31//usage: "\n -c Set controlling terminal to stdin" 32 33#include "libbb.h" 34 35int setsid_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 36int setsid_main(int argc UNUSED_PARAM, char **argv) 37{ 38 unsigned opt; 39 40 /* +: stop on first non-opt */ 41 opt = getopt32(argv, "^+" "c" "\0" "-1"/* at least one arg */); 42 argv += optind; 43 44 /* setsid() is allowed only when we are not a process group leader. 45 * Otherwise our PID serves as PGID of some existing process group 46 * and cannot be used as PGID of a new process group. 47 * 48 * Example: setsid() below fails when run alone in interactive shell: 49 * $ setsid PROG 50 * because shell's child (setsid) is put in a new process group. 51 * But doesn't fail if shell is not interactive 52 * (and therefore doesn't create process groups for pipes), 53 * or if setsid is not the first process in the process group: 54 * $ true | setsid PROG 55 * or if setsid is executed in backquotes (`setsid PROG`)... 56 */ 57 if (setsid() < 0) { 58 pid_t pid = fork_or_rexec(argv); 59 if (pid != 0) { 60 /* parent */ 61 /* TODO: 62 * we can waitpid(pid, &status, 0) and then even 63 * emulate exitcode, making the behavior consistent 64 * in both forked and non forked cases. 65 * However, the code is larger and upstream 66 * does not do such trick. 67 */ 68 return EXIT_SUCCESS; 69 } 70 71 /* child */ 72 /* now there should be no error: */ 73 setsid(); 74 } 75 76 if (opt) { 77 /* -c: set (with stealing) controlling tty */ 78 ioctl(0, TIOCSCTTY, 1); 79 } 80 81 BB_EXECVP_or_die(argv); 82} 83