openrc-shutdown: add dry-run option

man/openrc-shutdown.8

@@ -27,6 +27,9 @@ is the utility that communicates with openrc-init(8) to bring down the
 system or instruct openrc-init to re-execute itself. It supports the
 following options:
 .Bl -tag -width "poweroff"
+.It Fl d , -dry-run
+Print the action that would be taken without executing it. This is to
+allow testing.
 .It Fl H , -halt
 Stop all services, kill all remaining processes and halt the system.
 .It Fl k , -kexec

src/rc/openrc-shutdown.c

@@ -35,8 +35,9 @@
 
 const char *applet = NULL;
 const char *extraopts = NULL;
-const char *getoptstring = "HkpRr" getoptstring_COMMON;
+const char *getoptstring = "dHkpRr" getoptstring_COMMON;
 const struct option longopts[] = {
+	{ "dry-run",        no_argument, NULL, 'd'},
 	{ "halt",        no_argument, NULL, 'H'},
 	{ "kexec",        no_argument, NULL, 'k'},
 	{ "poweroff",        no_argument, NULL, 'p'},
@@ -45,6 +46,7 @@ const struct option longopts[] = {
 	longopts_COMMON
 };
 const char * const longopts_help[] = {
+	"print actions instead of executing them",
 	"halt the system",
 	"reboot the system using kexec",
 	"power off the system",
@@ -56,13 +58,16 @@ const char *usagestring = NULL;
 const char *exclusive = "Select one of "
 "--halt, --kexec, --poweroff, --reexec or --reboot";
 
-static void send_cmd(const char *cmd)
+static void send_cmd(const char *cmd, bool dryrun)
 {
 	FILE *fifo;
  	size_t ignored;
 
+	if (dryrun) {
+		einfo("Would send %s to init", cmd);
+		return;
+	}
 	fifo = fopen(RC_INIT_FIFO, "w");
-
 	if (!fifo) {
 		perror("fopen");
 		return;
@@ -78,6 +83,7 @@ int main(int argc, char **argv)
 {
 	int opt;
 	int cmd_count = 0;
+	bool do_dryrun = false;
 	bool do_halt = false;
 	bool do_kexec = false;
 	bool do_poweroff = false;
@@ -85,12 +91,13 @@ int main(int argc, char **argv)
 	bool do_reexec = false;
 
 	applet = basename_c(argv[0]);
-if (geteuid() != 0)
-	eerrorx("%s: you must be root\n", applet);
 	while ((opt = getopt_long(argc, argv, getoptstring,
 		    longopts, (int *) 0)) != -1)
 	{
 		switch (opt) {
+		case 'd':
+			do_dryrun = true;
+			break;
 		case 'H':
 			do_halt = true;
 			cmd_count++;
@@ -114,21 +121,23 @@ if (geteuid() != 0)
 		case_RC_COMMON_GETOPT
 		}
 	}
+if (geteuid() != 0 && ! do_dryrun)
+	eerrorx("%s: you must be root\n", applet);
 	if (cmd_count > 1) {
 		eerror("%s: %s\n", applet, exclusive);
 		usage(EXIT_FAILURE);
 	}
 	if (do_halt)
-		send_cmd("halt");
+		send_cmd("halt", do_dryrun);
 	else if (do_kexec)
-		send_cmd("kexec");
+		send_cmd("kexec", do_dryrun);
 	else if (do_poweroff)
-		send_cmd("poweroff");
+		send_cmd("poweroff", do_dryrun);
 	else if (do_reboot)
-		send_cmd("reboot");
+		send_cmd("reboot", do_dryrun);
 	else if (do_reexec)
-		send_cmd("reexec");
+		send_cmd("reexec", do_dryrun);
 	else
-		send_cmd("single");
+		send_cmd("single", do_dryrun);
 	return 0;
 }