1 files changed, 94 insertions, 0 deletions
diff --git a/catsit-watch.c b/catsit-watch.c
new file mode 100644
index 0000000..4d0840c
--- /dev/null
+++ b/catsit-watch.c
@@ -0,0 +1,94 @@
+/* Copyright (C) 2021  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <sys/types.h>
+
+#include <err.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/event.h>
+#include <sys/time.h>
+#include <sys/wait.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+static void watch(int kq, char *path) {
+	int fd = open(path, O_RDONLY | O_CLOEXEC);
+	if (fd < 0) err(EX_NOINPUT, "%s", path);
+
+	struct kevent event;
+	EV_SET(
+		&event, fd, EVFILT_VNODE, EV_ADD | EV_CLEAR,
+		NOTE_WRITE | NOTE_DELETE, 0, path
+	);
+	int nevents = kevent(kq, &event, 1, NULL, 0, NULL);
+	if (nevents < 0) err(EX_OSERR, "kevent");
+}
+
+static void run(char *argv[]) {
+	pid_t pid = fork();
+	if (pid < 0) err(EX_OSERR, "fork");
+	if (!pid) {
+		execvp(argv[0], argv);
+		err(126, "%s", argv[0]);
+	}
+
+	int status;
+	pid = wait(&status);
+	if (pid < 0) err(EX_OSERR, "wait");
+	if (WIFEXITED(status)) {
+		status = WEXITSTATUS(status);
+		if (status) exit(status);
+	} else {
+		exit(status);
+	}
+}
+
+int main(int argc, char *argv[]) {
+	int kq = kqueue();
+	if (kq < 0) err(EX_OSERR, "kqueue");
+	fcntl(kq, F_SETFD, FD_CLOEXEC);
+
+	int init = 0;
+	for (int opt; 0 < (opt = getopt(argc, argv, "f:i"));) {
+		switch (opt) {
+			break; case 'f': watch(kq, optarg);
+			break; case 'i': init = 1;
+			break; default: return EX_USAGE;
+		}
+	}
+	argc -= optind;
+	argv += optind;
+	if (!argc) errx(EX_USAGE, "command required");
+
+#ifdef __OpenBSD__
+	int error = pledge("stdio proc exec", NULL);
+	if (error) err(EX_OSERR, "pledge");
+#endif
+
+	if (init) run(argv);
+	for (;;) {
+		struct kevent event;
+		int nevents = kevent(kq, NULL, 0, &event, 1, NULL);
+		if (nevents < 0) err(EX_OSERR, "kevent");
+
+		if (event.fflags & NOTE_DELETE) {
+			errx(EX_TEMPFAIL, "%s: file removed", (char *)event.udata);
+		}
+		run(argv);
+	}
+}