Added some of the initial implementation

1 files changed, 84 insertions, 1 deletions

diff --git a/supervise.c b/supervise.c
index 3bae8cf..95ede21 100644
--- a/supervise.c
+++ b/supervise.c
@@ -3,19 +3,102 @@
 #include <unistd.h>
 #include <errno.h>
 #include <err.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/file.h>
+#include <sys/wait.h>
 
 char *const run_path[] = { "./run", NULL };
 
+void
+start_proc()
+{
+	pid_t p = fork();
+	if (p == 0) {
+		execv(run_path[0], run_path);
+	} else if (p > 0) {
+		waitpid(p, NULL, 0);
+	} else {
+		err(1, "fork()");
+	}
+}
+
+int
+acquire_lock()
+{
+	int lock_fd;
+
+	if ((lock_fd = open("supervise/lock", O_CREAT | O_TRUNC | O_RDONLY, 0600)) == -1)
+		err(1, "open()");
+
+	if (flock(lock_fd, LOCK_EX | LOCK_NB) == -1) {
+		if (errno == EWOULDBLOCK) {
+			fprintf(stderr, "Could not acquire lock\n");
+			exit(1);
+		} else {
+			err(1, "flock()");
+		}
+	}
+
+	return lock_fd;
+}
+
+void
+update_status()
+{
+	int fd, r;
+	unsigned char status[18];
+
+	if ((fd = open("supervise/status.new", O_CREAT | O_TRUNC | O_WRONLY | 0644)) == -1) {
+		perror("open()");
+		return;
+	}
+
+	if ((r = write(fd, status, sizeof(status))) == -1)
+		perror("write()");
+
+	if (close(fd) == -1)
+		perror("close()");
+
+	if (r < sizeof(status)) {
+		fprintf(stderr, "Failed to fully write status.new\n");
+
+		if (unlink("supervise/status.new") == -1)
+			perror("unlink()");
+
+		return;
+	}
+
+	if (rename("supervise/status.new", "supervise/status") == -1)
+		perror("rename()");
+}
+
 int
 main(int argc, char **argv)
 {
+	int lock_fd;
+
 	if (argc != 2)
 		errx(1, "Usage: %s <dir>\n", argv[0]);
 
 	if (chdir(argv[1]) == -1)
 		err(1, "chdir()");
 
-	execv(run_path[0], run_path);
+	if (mkdir("supervise", 0700) == -1 && errno != EEXIST)
+		err(1, "mkdir()");
+
+	lock_fd = acquire_lock();
+
+	if (mkfifo("supervise/control", 0600) == -1 && errno != EEXIST)
+		err(1, "mkfifo()");
+
+	if (mkfifo("supervise/ok", 0600) == -1 && errno != EEXIST)
+		err(1, "mkfifo()");
+
+	start_proc(); /* XXX: Main loop goes here */
+
+	if (close(lock_fd) == -1)
+		perror("close()");
 
 	return 0;
 }