Dry-Run Engineering: The Simple Practice That Prevents Production Disasters

There is a post trending on Hacker News today about the --dry-run flag. Henrik Warne writes about adding it to a reporting application early in development and being surprised by how useful it became. I have been nodding along because this matches my experience exactly. The --dry-run pattern is one of those deceptively simple engineering practices that punches well above its weight. If you have ever run rsync --dry-run before committing to a massive file sync, or used terraform plan before terraform apply , you already know the value. What dry-run actually means A dry-run flag tells your script to show what it would do without actually doing it. Print the files that would be deleted. Log the API calls that would be made. Display the database rows that would be updated. Then exit without changing anything. The key principle: make it safe to run without thinking . When a colleague asks "what will this script do?", you should be able to run it with --dry-run and show them. No risk. No cle