A bin/witness

@@ -0,0 +1,23 @@ 
+#!/bin/sh
+#
+# witness - watch a file for changes & run a command
+
+file="$1"
+shift
+command="$@"
+
+get_access_time() {
+    stat -c %Z "$1"
+}
+
+ltime="$(get_access_time "$file")"
+
+while true; do
+    atime="$(get_access_time "$file")"
+    if [ "$atime" != "$ltime" ]; then
+        printf "witness: '%s' changed, running '%s'\n" "$file" "$command"
+        $command
+	ltime="$atime"
+    fi
+    sleep 0.5
+done