test: extend start-stop-serv test w/ all supported combinations

serv: add support for foregrounding, running with and without PID file,
      including custom PID filename.

test: verify Finit can start & monitor services that:
      1) Fork and creates a PID file in a known location
      2) Don't fork and don't create a PID file, but Finit does
      3) Don't fork but create a PID file
      4) Don't fork and create custom named PID file

Note: Finit cannot support a service that forks and doesn't create a PID
      file.  This combination is impossible to support without tracking
      all processes created in /proc -- which Finit does not do atm.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

test/common/serv.c

@@ -1,4 +1,9 @@
-/* Basic forking UNIX daemon with no options to run in foreground */
+/*
+ * Basic UNIX daemon
+ *
+ * Options to run in foreground and to create a PID file.  When running
+ * in foregrund it does not create a PID file by default.
+ */
 
 #include <err.h>
 #include <paths.h>
@@ -8,43 +13,93 @@
 #include <string.h>
 #include <unistd.h>
 
+#define PROGNM "serv"
+
 static void sig(int signo)
 {
 	warnx("We got signal %d ...", signo);
 	exit(0);
 }
 
-static void pidfile(char *nm)
+static void pidfile(char *pidfn)
 {
 	char fn[80];
 	pid_t pid;
 	FILE *fp;
 
-	if (!nm)
-		nm = "serv";
-
-	snprintf(fn, sizeof(fn), "%s%s.pid", _PATH_VARRUN, nm);
+	if (!pidfn) {
+		snprintf(fn, sizeof(fn), "%s%s.pid", _PATH_VARRUN, PROGNM);
+		pidfn = fn;
+	}
 	pid = getpid();
-	warnx("Creating PID file %s with %d", fn, pid);
+	warnx("Creating PID file %s with %d", pidfn, pid);
 
-	fp = fopen(fn, "w");
+	fp = fopen(pidfn, "w");
 	if (!fp)
 		exit(1);
 	fprintf(fp, "%d\n", pid);
 	fclose(fp);
 }
 
-int main(void)
+static int usage(int rc)
 {
+	FILE *fp = rc ? stderr : stdout;
+
+	fprintf(fp,
+		"%s [-nhp] [-P FILE]\n"
+		"\n"
+		" -n       Run in foreground\n"
+		" -h       Show help text (this)\n"
+		" -p       Create PID file despite running in foreground\n"
+		" -P FILE  Create PID file using FILE\n"
+		"\n"
+		"By default this program daemonizes itself to the background, and,\n"
+		"when it's done setting up its signal handler(s), creates a PID file\n"
+		"to let the rest of the system know it's done.  When the program runs\n"
+		"in the foreground it does not create a PID file by default.\n",
+		PROGNM);
+
+	return rc;
+}
+
+int main(int argc, char *argv[])
+{
+	int do_background = 1;
+	int do_pidfile = 1;
+	char *pidfn = NULL;
+	int c;
+
+	while ((c = getopt(argc, argv, "hnpP:")) != EOF) {
+		switch (c) {
+		case 'h':
+			return usage(0);
+		case 'n':
+			do_background = 0;
+			do_pidfile--;
+			break;
+		case 'p':
+			do_pidfile++;
+			break;
+		case 'P':
+			pidfn = optarg;
+			break;
+		default:
+			return usage(1);
+		}
+	}
+
 	/* Daemonize, fork to background etc. */
-	if (daemon(0, 1))
-		return 1;
+	if (do_background) {
+		if (daemon(0, 1))
+			return 1;
+	}
 
 	/* Signal handlers first *then* PID file */
 	signal(SIGTERM, sig);
 
-	/* Tell finit where we really are */
-	pidfile(NULL);
+	/* Tell world where we are, but not if bg w/o pid file */
+	if (do_pidfile == 1)
+		pidfile(pidfn);
 
 	warnx("Entering while(1) loop");
 	while (1)