rn — A Fast, Safe, Intent-Aware Rename Utility

rn is a small command-line tool for renaming files by inference.
You provide the new name, and rn determines the old name — safely, predictably, and fast.

It streamlines common workflows like:

• Changing file extensions: data.txt → data.csv
• Adding tags or versions: file.txt → file_backup.txt
• Creating backups: Makefile → Makefile.bak

$ ls
route_report.csv

$ rn route_report_before.csv
route_report.csv → route_report_before.csv

How rn Works

rn uses two complementary matching strategies to infer which file you want to rename:

1. Extension Change

Matches when the base name is identical but the extension differs.

Examples:

$ rn data.csv
data.txt → data.csv

$ rn report.md
report.txt → report.md

$ rn all_aero_pools.csv
all_aero_pools.txt → all_aero_pools.csv

Rules:

• Both files must have an extension (contain a dot)
• Everything before the last dot must match exactly
• Only the extension part differs

2. Expansion

Matches when characters are added in the middle or end of the filename.

Examples:

$ rn route_report_before.csv
route_report.csv → route_report_before.csv

$ rn data_backup.json
data.json → data_backup.json

$ rn Makefile.bak
Makefile → Makefile.bak

$ rn config~
config → config~

Rules:

• The new name must be longer than the old name
• All characters from the old name must appear in order (prefix + suffix match)
• Characters are added in the middle or at the end
• Expansion at the start is not allowed (prevents ambiguous matches)

Safety Requirements

For any rename to succeed:

• Exactly one file must match — no guessing among multiple candidates
• Target must not exist — unless --force is used
• At least one pattern must match — extension change OR expansion

Examples

Extension Changes

$ rn data.csv
data.txt → data.csv

$ rn image.jpg
image.png → image.jpg

$ rn config.yaml
config.yml → config.yaml

Adding Tags or Versions

$ rn image_before.png
image.png → image_before.png

$ rn results_v2.csv
results.csv → results_v2.csv

$ rn report_final.txt
report.txt → report_final.txt

Backup Patterns

$ rn Makefile.bak
Makefile → Makefile.bak

$ rn config~
config → config~

$ rn script.sh.bak
script.sh → script.sh.bak

Bidirectional Renames

# Expansion
$ rn route_report_before.csv
route_report.csv → route_report_before.csv

# Reduction (reverse expansion)
$ rn route_report.csv
route_report_before.csv → route_report.csv

Ambiguous Cases & Limitations

⚠️ Multiple Matches (Refused)

When multiple files could match, rn refuses to guess:

$ ls
report.csv  report.txt  report.md

$ rn report.json
Multiple candidates found for 'report.json':
  report.csv
  report.txt
  report.md

Cannot proceed - ambiguous match.

Solution: Be more specific or rename manually with mv.

⚠️ Similar Extensions (May Match Both Patterns)

Some renames match both extension change AND expansion:

$ rn config.yaml
# Matches extension change: config.(yml) → config.(yaml)
# Also matches expansion: config.yml → config.yaml (yml is prefix of yaml)
# Result: Works fine! (we use OR logic)

This is harmless — the rename succeeds either way.

⚠️ No Prefix Expansion

rn does NOT match when adding a prefix:

$ ls
test.log

$ rn production_test.log
No matching files found for 'production_test.log'
# Rejected: expansion at the start is not allowed

Rationale: Prevents ambiguous matches like data.json matching metadata.json.

⚠️ Files Without Extensions

Extension change requires both files to have extensions:

$ ls
README

$ rn README.md
README → README.md  # Works! (expansion pattern)

$ ls
Makefile  LICENSE

$ rn LICENSE
Makefile → LICENSE  # FAILS (different base, no match)

⚠️ Overlapping Names

Be careful with files that are substrings of each other:

$ ls
test.txt  testing.txt

$ rn test.csv
test.txt → test.csv  # Works

$ rn testing.csv
testing.txt → testing.csv  # Works

$ rn tester.txt
# May match test.txt via expansion (test → tester)

Best Practice: In directories with many similar names, verify the match before confirming.

Options

rn <new_name> [OPTIONS]

OPTIONS:
  -f, --force    Force rename even if target exists (overwrites)
  -h, --help     Print help information

Safety Guarantees

• No wild guessing: Requires exactly one matching file
• No overwrite: Refuses if the target already exists (unless --force)
• No ambiguity: Prints all candidates and exits when multiple files match
• Atomic rename: Uses the OS rename syscall for safe file operations

rn is designed for interactive use and safety, not for risky batch scripts.

Installation

cargo install snipren

Or build from source:

git clone https://github.com/jac18281828/snipren
cd snipren
cargo build --release
cp target/release/rn ~/.local/bin/  # or anywhere in your $PATH

Why rn?

• Faster than mv: No need to type both the old and new names
• Intent-aware: Understands common rename patterns (extensions, tags, backups)
• Safe by default: Won't rename if there's any ambiguity
• Simple: Just type the name you want, rn figures out the rest

mv requires you to know both names.
rn lets you rename using the name you want, not the name you must type.
Fast for humans, safe by design.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

See LICENSE file for details.