Two scheduled jobs nobody could account for

A cron listing with eleven entries, of which two called commands that no longer existed.

$ crontab -l | grep -oP '^S+ S+ S+ S+ S+ K.*' | while read -r c; do
    ./bin/command-exists "$c" || echo "missing: $c"
  done
  missing: php artisan subscriptions:recalculate
  missing: php artisan subscriptions:expire

# both had been failing nightly since June, into a log
# nobody reads, with a non-zero exit that nothing
# checked.

A cron job whose command does not exist fails silently unless something checks the exit code, and cron’s own mechanism for that is an email nobody configured. The command-exists check is the same one that keeps the runbooks honest and it took ten minutes to point at the crontab as well.