Add watch.c

2 files changed, 101 insertions, 0 deletions

diff --git a/home/.bin/watch.c b/home/.bin/watch.c
new file mode 100755
index 00000000..7720315b
--- /dev/null
+++ b/home/.bin/watch.c
@@ -0,0 +1,100 @@
+#if 0
+exec cc -Wall -Wextra -Wpedantic -o $(dirname $0)/watch $0
+#endif
+
+/*
+ * Execute a command each time files change.
+ *
+ * Copyright (c) 2017, June McEnroe <programble@gmail.com>
+ *
+ * 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 <stdlib.h>
+#include <sys/event.h>
+#include <sys/wait.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+static void watch(int kq, char *path) {
+    int fd = open(path, O_RDONLY);
+    if (fd < 0) err(EX_IOERR, "%s", path);
+
+    struct kevent event = {
+        .ident = fd,
+        .filter = EVFILT_VNODE,
+        .flags = EV_ADD | EV_CLEAR,
+        .fflags = NOTE_WRITE | NOTE_DELETE,
+        .udata = path,
+    };
+    int nevents = kevent(kq, &event, 1, NULL, 0, NULL);
+    if (nevents < 0) err(EX_IOERR, "kevent");
+}
+
+static void exec(char *const argv[]) {
+    pid_t pid = fork();
+    if (pid < 0) err(EX_OSERR, "fork");
+
+    if (!pid) {
+        execvp(argv[0], argv);
+        err(EX_OSERR, "%s", argv[0]);
+    }
+
+    int status;
+    pid = wait(&status);
+    if (pid < 0) err(EX_OSERR, "wait");
+
+    if (WIFEXITED(status)) {
+        warnx("exit %d", WEXITSTATUS(status));
+    } else if (WIFSIGNALED(status)) {
+        warnx("signal %d", WTERMSIG(status));
+    } else {
+        warnx("status %d", status);
+    }
+}
+
+int main(int argc, char *argv[]) {
+    if (argc < 3) return EX_USAGE;
+
+    int kq = kqueue();
+    if (kq < 0) err(EX_OSERR, "kqueue");
+
+    int index;
+    for (index = 1; index < argc - 1; ++index) {
+        if (argv[index][0] == '-') {
+            index++;
+            break;
+        }
+        watch(kq, argv[index]);
+    }
+
+    exec(&argv[index]);
+
+    for (;;) {
+        struct kevent event;
+        int nevents = kevent(kq, NULL, 0, &event, 1, NULL);
+        if (nevents < 0) err(EX_IOERR, "kevent");
+
+        if (event.fflags & NOTE_DELETE) {
+            close(event.ident);
+            watch(kq, event.udata);
+        }
+
+        exec(&argv[index]);
+    }
+}
diff --git a/link.sh b/link.sh
index 9d012182..802aec11 100755
--- a/link.sh
+++ b/link.sh
@@ -30,6 +30,7 @@ link '.bin/sup'
 link '.bin/tup'
 link '.bin/up'
 link '.bin/wake.c'
+link '.bin/watch.c'
 link '.bin/xx.c'
 link '.config/git/config'
 link '.config/git/ignore'