nlsockd: add support for single run (-s)

Add suport for running the helper exactly once. This is useful
when you wait for a specific block device to show up, for example
from initramfs script that looks for the device specified as
root=... boot option.

1 files changed, 15 insertions, 3 deletions

diff --git a/nlsockd.c b/nlsockd.c
index 481eebd..e4a04ce 100644
--- a/nlsockd.c
+++ b/nlsockd.c
@@ -102,7 +102,7 @@ init_netlink_socket(void)
 void
 usage(void)
 {
-	errx(1, "usage: %s runpath [...]\n", argv0);
+	errx(1, "usage: %s [-s] runpath [...]\n", argv0);
 
 }
 
@@ -110,12 +110,19 @@ int
 main(int argc, char *argv[])
 {
 	struct pollfd fds;
+	int single_run = 0;
 
 	ARGBEGIN {
+	case 's':
+		single_run = 1;
+		break;
 	default:
 		usage();
 	} ARGEND;
 
+	if (argv[0] == NULL)
+		usage();
+
 	fds.events = POLLIN;
 	fds.fd = init_netlink_socket();
 
@@ -123,9 +130,14 @@ main(int argc, char *argv[])
 
 	while (poll(&fds, 1, -1) > -1) {
 		if (fds.revents & POLLIN) {
-			int status;
+			int status, r;
 			pid_t childpid = spawn_handler(fds.fd, argv);
-			waitpid(childpid, &status, 0);
+			r = waitpid(childpid, &status, 0);
+			if(r == -1) {
+				warn("waitpid(%d)", childpid);
+			} else if (single_run && WIFEXITED(status)) {
+				return WEXITSTATUS(status);
+			}
 		}
 	}