Shell Scripts

You can easily add Cron monitoring monitoring to a shell script. All you have to do is make a HTTP request at the end of the script. curl and wget are two common command line HTTP clients you can use.

# Sending a HTTP GET request with curl:
curl --retry 3

# Silent version (no stdout/stderr output unless curl hits an error):
curl -fsS --retry 3

# Sending a HTTP GET request with wget:
wget -O /dev/null

Signalling Failure from Shell Scripts

You can append /fail to any ping URL and use the resulting URL to actively signal a failure. The below example:

  • runs /usr/bin/certbot renew
  • if the certbot command is successful (exit code 0), send HTTP GET to
  • otherwise, send HTTP GET to

# Payload here:
/usr/bin/certbot renew
# Ping Cron monitoring
curl --retry 3 "$([ $? -ne 0 ] && echo -n /fail)"

Logging Command Output

When pinging with HTTP POST, you can put extra diagnostic information in request body. If the request body looks like a valid UTF-8 string, Cron monitoring will accept and store first 10KB of the request body.

In the below example, certbot's output is captured and submitted via HTTP POST:


m=$(/usr/bin/certbot renew 2>&1)
curl -fsS --retry 3 -X POST --data-raw "$m"