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 adding _before, _after, dates, tags, or variants to filenames without retyping the original name.

$ ls
route_report.csv

$ rn route_report_before.csv
# renames: route_report.csv → route_report_before.csv

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How rn Works

1. Expansion

Expansion happens when the target name begins with the full current name.

Example:

old: route_report.csv
new: route_report_before.csv

Rules:

• If new_name starts with old_name
• If ending is identical of both files
• If exactly one file matches: rename it.
• If zero or multiple matches: no action; an explanation is printed.

Safety Guarantees

• No wild guessing: requires exactly one match.
• No overwrite: refuses if the target already exists (unless --force is used).
• No ambiguity: prints candidate files and exits when unsure.
• Atomic rename using the OS rename syscall.

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

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Examples

Add a tag

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

Add a version

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

Safe reduction

$ rn report.csv
route_report_before.csv → report.csv   # only candidate

Ambiguous reduction (refused)

$ rn route.csv
Multiple candidates:
  route_report_before.csv
  route_raw.csv

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Installation

cargo install rn

Or download binaries from Releases and place in your $PATH.

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Why rn?

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.