1 files changed, 82 insertions, 0 deletions
diff --git a/util-linux/setsid.c b/util-linux/setsid.c
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+++ b/util-linux/setsid.c
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+/* vi: set sw=4 ts=4: */
+/*
+ * setsid.c -- execute a command in a new session
+ * Rick Sladkey <jrs@world.std.com>
+ * In the public domain.
+ *
+ * 1999-02-22 Arkadiusz Mickiewicz <misiek@pld.ORG.PL>
+ * - added Native Language Support
+ *
+ * 2001-01-18 John Fremlin <vii@penguinpowered.com>
+ * - fork in case we are process group leader
+ *
+ * 2004-11-12 Paul Fox
+ * - busyboxed
+ */
+//config:config SETSID
+//config:	bool "setsid"
+//config:	default y
+//config:	help
+//config:	  setsid runs a program in a new session
+
+//applet:IF_SETSID(APPLET(setsid, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_SETSID) += setsid.o
+
+//usage:#define setsid_trivial_usage
+//usage:       "[-c] PROG ARGS"
+//usage:#define setsid_full_usage "\n\n"
+//usage:       "Run PROG in a new session. PROG will have no controlling terminal\n"
+//usage:       "and will not be affected by keyboard signals (^C etc).\n"
+//usage:     "\n	-c	Set controlling terminal to stdin"
+
+#include "libbb.h"
+
+int setsid_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int setsid_main(int argc UNUSED_PARAM, char **argv)
+{
+	unsigned opt;
+
+	opt_complementary = "-1"; /* at least one arg */
+	opt = getopt32(argv, "+c"); /* +: stop on first non-opt */
+	argv += optind;
+
+	/* setsid() is allowed only when we are not a process group leader.
+	 * Otherwise our PID serves as PGID of some existing process group
+	 * and cannot be used as PGID of a new process group.
+	 *
+	 * Example: setsid() below fails when run alone in interactive shell:
+	 *  $ setsid PROG
+	 * because shell's child (setsid) is put in a new process group.
+	 * But doesn't fail if shell is not interactive
+	 * (and therefore doesn't create process groups for pipes),
+	 * or if setsid is not the first process in the process group:
+	 *  $ true | setsid PROG
+	 * or if setsid is executed in backquotes (`setsid PROG`)...
+	 */
+	if (setsid() < 0) {
+		pid_t pid = fork_or_rexec(argv);
+		if (pid != 0) {
+			/* parent */
+			/* TODO:
+			 * we can waitpid(pid, &status, 0) and then even
+			 * emulate exitcode, making the behavior consistent
+			 * in both forked and non forked cases.
+			 * However, the code is larger and upstream
+			 * does not do such trick.
+			 */
+			return EXIT_SUCCESS;
+		}
+
+		/* child */
+		/* now there should be no error: */
+		setsid();
+	}
+
+	if (opt) {
+		/* -c: set (with stealing) controlling tty */
+		ioctl(0, TIOCSCTTY, 1);
+	}
+
+	BB_EXECVP_or_die(argv);
+}