Get a push notification when a cron job finishes

Silent jobs are the dangerous ones

Cron's default behavior is to say nothing. A job that quietly stopped running three weeks ago looks exactly like one that's working — until the day you reach for the backup that was never made. The classic fix is to email yourself, but nobody reads cron email, and half the time the mailer isn't even configured on the box.

A push notification is different: it's on your phone, it's immediate, and it's impossible to ignore. You don't need it to fire every night — you need it to fire when the job finishes so you can trust the silence the rest of the time, or the moment it fails so you can act.

The one-line version

Lert gives you a unique URL. Anything that can make an HTTP request can POST to it. Add this to the end of the script your cron entry runs:

curl -X POST "https://lert.dev/p/your-id" \
  -H "Content-Type: application/json" \
  -d '{"title":"Nightly backup done","body":"db + uploads · 4.2 GB","tag":"cron"}'

The tag field is a free-form label — set it to cron or the job's name and every run shows up grouped in your in-app history. No auth token, no SDK. Replace your-id with your endpoint and you're done.

Set it up in three steps

1. Copy your Lert URL

Open the Lert app and copy your unique endpoint — something like https://lert.dev/p/your-id. Treat it like a password; anyone who has it can notify you, and you can regenerate it any time.

2. Wrap the job so it reports success or failure

The most useful pattern is to check the exit code and send different text for each outcome. Put this in a small wrapper script:

#!/usr/bin/env bash
URL="https://lert.dev/p/your-id"

if /usr/local/bin/run-backup.sh; then
  curl -X POST "$URL" -H "Content-Type: application/json" \
    -d '{"title":"Backup ✅","body":"Completed at '"$(date +%H:%M)"'","tag":"backup"}'
else
  curl -X POST "$URL" -H "Content-Type: application/json" \
    -d '{"title":"Backup ❌ FAILED","body":"Exit code '"$?"' — needs you","tag":"backup"}'
fi

3. Point cron at the wrapper

Add a single line to your crontab with crontab -e. This runs the backup every night at 3:00am; the notify calls are baked into the script it invokes:

# m h  dom mon dow   command
0 3 * * *  /home/deploy/backup.sh

That's it. When cron fires the job, you get a real iOS push — it wakes a locked phone and buzzes a paired Apple Watch, usually within a second. Even at 3am on a headless server on the other side of the world.

Notify only when it matters

If a nightly job succeeds every night, a nightly success push gets tuned out fast. A common refinement is to stay quiet on success and only shout on failure using a || guard — that way a buzz always means "look now":

30 2 * * *  /home/deploy/sync.sh || curl -X POST "https://lert.dev/p/your-id" \
  --data-binary "Sync FAILED on $(hostname) at $(date +%H:%M)" \
  -H "Content-Type: text/plain"

Why Lert for cron alerts

Cron notification usually means wrestling with sendmail, a monitoring SaaS, or a heartbeat service that needs its own account and dashboard. Lert is one HTTP request from a shell script — no daemon, no agent, no key. The endpoint URL is the authentication, so putting a heartbeat on every scheduled job is genuinely one line of work.