diff --git a/src/scrape-event.js b/src/scrape-event.js
index 8083f02..74c93d6 100644
--- a/src/scrape-event.js
+++ b/src/scrape-event.js
@@ -1,4 +1,9 @@
-const { parse_args, sleep } = require('./logic');
+const {
+  parse_args,
+  sleep,
+  read_previous_events,
+  write_events,
+} = require('./logic');
 
 const { get_event_details } = require('./facebook-event.js');
 const { get_page_events } = require('./facebook-page-events.js');
@@ -8,14 +13,20 @@ const { omit } = require('ramda');
 const options = parse_args(process.argv.slice(2));
 
 (async () => {
+  const previous_events = await read_previous_events(options.events);
   const page_events = await get_page_events(options);
 
   let events = [];
 
   for (const event of page_events) {
-    sleep(2);
-    const event_details = await get_event_details(event.id);
-    events.push({ ...event, ...event_details });
+    const index = previous_events.findIndex(({ id }) => event.id === id);
+    if (index === -1) {
+      sleep(2);
+      const event_details = await get_event_details(event.id);
+      events.push({ ...event, ...event_details });
+    } else {
+      events.push(previous_events[index]);
+    }
   }
 
   const filterAwayFields = omit([
@@ -47,5 +58,16 @@ const options = parse_args(process.argv.slice(2));
 
   events = events.map(filterAwayFields);
 
-  console.log(JSON.stringify(events));
+  if (options.output === null) {
+    console.log(JSON.stringify(events));
+    process.exit();
+  }
+
+  try {
+    await write_events(options.output, events);
+    process.exit();
+  } catch (e) {
+    console.error(e);
+    process.exit(1);
+  }
 })();