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Error-First Pattern: Writing Self-Documenting Bash

There’s a pattern in shell scripts that makes code harder to read than it needs to be. It looks like this:

if [[ -f "$config_file" ]]; then
  if [[ -r "$config_file" ]]; then
    source "$config_file"
    if [[ -n "$DATABASE_URL" ]]; then
      connect_to_database
      if [[ $? -eq 0 ]]; then
        run_migrations
        # ... and so on
      else
        echo "Connection failed" >&2
        exit 1
      fi
    else
      echo "DATABASE_URL not set" >&2
      exit 1
    fi
  else
    echo "Config not readable" >&2
    exit 1
  fi
else
  echo "Config not found" >&2
  exit 1
fi

You’ve seen this. You’ve probably written this. I haven’t. Sorry, not sorry.