rep

rep is a fast find-and-replace tool, based on fastmod.

Features plain and regex replacement, case-aware rewrites, interactive preview, line deletion, file listing, stdin mode, and multiple replacements in one pass.

By default rep prints a diff without touching the filesystem; pass --write to apply changes or --preview to step through them interactively.

Install

macOS / Linux

brew install gechr/tap/rep

Windows

scoop bucket add gechr https://github.com/gechr/scoop-bucket
scoop install gechr/rep

Cargo

cargo install --git https://github.com/gechr/rep

Usage

Examples

# Replace "1.2.3" with "4.5.6" in all files
rep 1.2.3 4.5.6

# Replace "foo" with "bar" in "*.txt" files
rep -f txt foo bar

# Replace "foo" with "bar" in all (hidden) files
rep --hidden foo bar

# Replace "foo" with "bar" in all (hidden) Dockerfiles
rep -f '=Dockerfile' --hidden foo bar

# Replace "foo" with "bar" in all files and preview changes
rep --preview foo bar

# Replace "1.2.3" and "3.2.1" with "4.5.6" in all files
rep --regex '[13]\.2\.[13]' 4.5.6

# Swap "foo.bar" with "bar.foo" in all files
rep --regex '(foo)\.(bar)' '$2.$1'

# Replace "f.oo" and "F.OO" with "bar"
rep --ignore-case 'f.oo' bar

# Smart-replace in all files:
#  "foo_bar" with "hello_world"
#  "FooBar"  with "HelloWorld"
#  "FOO_BAR" with "HELLO_WORLD"
rep --smart foo_bar hello_world

# Read from stdin and replace "foo" with "bar"
echo foo bar | rep foo bar
rep foo bar < foobar.txt

# Apply multiple replacements in one pass
rep -e foo bar -e baz qux src

# Delete every line containing "TODO"
rep -d TODO

# Print only the total number of replacements without modifying files
rep --dry-run --count foo bar

# Apply replacements and print only the total
rep --write --count foo bar

Run rep --help for the full reference, including the styling and hyperlink flags.

Case-aware replacement

rep offers two strategies for case-aware replacement. They solve different problems and are mutually exclusive - passing both flags on the command line is an error. A value in ~/.config/rep/config.toml or a REP_* env var can still be overridden by either flag on the command line.

-S, --smart - identifier renames across naming conventions

Generates the standard identifier case variants of <find> and <replace> (snake_case, camelCase, PascalCase, kebab-case, SCREAMING_SNAKE_CASE, Train-Case, Ada_Case) and rewrites whichever variant appears in the source to the matching variant of the replacement.

rep --smart foo_bar hello_world

Source	Output
foo_bar	hello_world
fooBar	helloWorld
FooBar	HelloWorld
FOO_BAR	HELLO_WORLD
foo-bar	hello-world

Use --smart when renaming an identifier across a codebase that uses several naming conventions for the same logical concept.

-P, --preserve - mirror the source's letter case

Matches the pattern case-insensitively as a literal string, then projects the source's letter-case shape onto the replacement: lowercase, Titlecase, UPPERCASE. Anything else (mixed case) falls back to the replacement as authored.

rep --preserve colour color

Source	Output	Shape
colour	color	lowercase
Colour	Color	Titlecase
COLOUR	COLOR	UPPERCASE
cOlOuR	color	mixed → as-authored

Use --preserve for prose, docs, or string-literal rewrites where the same word appears in different case shapes and you want the replacement to follow each one.

Configuration

rep reads defaults from ~/.config/rep/config.toml (or $XDG_CONFIG_HOME/rep/config.toml). The file uses TOML; keys mirror the CLI flag names in kebab-case.

# ~/.config/rep/config.toml
hidden = true
ignore-case = true
preview-tool = "delta"
hyperlink-format = "vscode"

Precedence is config file < environment variable < CLI flag. Each configurable flag has a matching REP_* env var (e.g. REP_HIDDEN, REP_PREVIEW_TOOL), accepting 1/0/true/false/yes/no/on/off for booleans.

Set REP_CONFIG_PATH to use a different file (e.g. for project-local config), or set it to an empty string to disable config loading entirely.

REP_CONFIG_PATH=./rep.toml rep foo bar