This script was born out of a desire to monitor and alert on cronjobs using
Prometheus and Alertmanager.

This script was inspired by https://janikvonrotz.ch/2020/09/07/monitor-cron-jobs-with-prometheus-grafana-and-node-exporter/

As far as I'm aware there isn't another facility for exposing metrics related
to this in Node Exporter.

This script receives two arguments, the description of the cronjob as a string
and the exit status of the previous command. It prints the metric to stdout.

Usage:

```bash
<command> ; cronjob "<description>" $?
```

Example crontab entry:

```
* * * * * echo "Hello world!"; cronjob "greeting" $? | sponge /var/lib/prometheus/node-exporter/cronjob_greeting.prom
```

Example textfile:

```
[vagrant@rocky8 ~]$ cat /var/lib/prometheus/node-exporter/cronjob_greeting.prom
node_cronjob_status{user="vagrant", description="greeting"} 0
```

Signed-off-by: Alex Kraker <[email protected]>

Give this script a more descriptive name. This script will be seen in
crontab files and this will be more descriptive of what the script is
doing.

Signed-off-by: Alex Kraker <[email protected]>

Signed-off-by: Alex Kraker <[email protected]>