repren

repren does in one safe, previewable pass what hand edits and sed/perl/awk loops do awkwardly: combined content and file/directory renames, simultaneous multi-pattern replacement (including swaps), case-variant-aware refactoring, and atomic writes with backups and undo.

If you are going to use repren, read its docs first: run repren --docs for the full flags, pattern-file format, examples, and edge cases. This skill only tells you when to reach for repren and which command; repren --docs and repren --help carry the how.

Invocation: use repren if it is on PATH, otherwise uvx repren@latest (no install needed, zero runtime dependencies). Always preview with --dry-run first.

When to use repren

Prefer repren over the Edit tool or shell loops whenever a rename or replacement spans more than a file or two. Reach for it when the task is to:

• Rename a symbol across many files — repren --from=Old --to=New --word-breaks --full DIR
• Rename a symbol and the files/directories named after it, together — --full rewrites contents and renames paths in one pass
• Apply many replacements at once, or swap names (foo↔bar) — repren --patterns=FILE --full DIR
• Refactor an identifier across all case variants (camelCase/snake_case/PascalCase/UPPER_CASE) — add --preserve-case
• Replace with a regex and capture groups across files — repren --from='figure ([0-9]+)' --to='Figure \1' DIR
• Make a bulk change you must preview, back up, and be able to reverse — --dry-run, then run, then --undo or --clean-backups

For the exact flags, pattern-file syntax, scoping (--include/--exclude, --literal, --at-once), and JSON output, read repren --docs.

When not to use repren

• A single-file or one-off edit — use the Edit tool.
• Language-aware or semantic refactors — use an AST tool such as ast-grep.
• Anything needing precise line-by-line control — use the Edit tool.

Good to know

• Always --dry-run first. repren writes atomically and leaves .orig backups; --undo restores them, --clean-backups removes them.
• repren does not read .gitignore. It skips dotfiles (including .git/) by default; scope everything else explicitly with --include/--exclude. See repren --docs.