rgx

regex101, but in your terminal

A terminal regex debugger with real-time matching, capture group highlighting, and plain-English explanations. Written in Rust.

demo

Features

Real-time matching — matches update on every keystroke
3 regex engines — Rust regex (default), fancy-regex (lookaround/backrefs), PCRE2 (full features)
Capture group highlighting — distinct colors per group, nested group support
Plain-English explanations — walks the regex AST to generate human-readable breakdowns
Engine selector — switch engines with Ctrl+E, see where behavior differs
Regex flags — toggle case-insensitive, multiline, dotall, unicode, extended
Stdin pipe support — echo "test string" | rgx '\d+'
Cross-platform — Linux, macOS, Windows

Installation

From crates.io

cargo install rgx-cli

From prebuilt binaries

Download from GitHub Releases.

Shell installer

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/brevity1swos/rgx/releases/latest/download/rgx-installer.sh | sh

Homebrew

brew install brevity1swos/tap/rgx

From source

git clone https://github.com/brevity1swos/rgx.git
cd rgx
cargo install --path .

Without PCRE2 (zero C dependencies)

cargo install rgx-cli --no-default-features

Usage

# Interactive mode
rgx

# Start with a pattern
rgx '\d{3}-\d{3}-\d{4}'

# Pipe text from stdin
echo "Call 555-123-4567 or 555-987-6543" | rgx '\d{3}-\d{3}-\d{4}'

# Use a specific engine
rgx --engine fancy '\w+(?=@)'

# With flags
rgx -i 'hello'

Keyboard Shortcuts

Key	Action
`Tab`	Switch between pattern / test string
`Ctrl+E`	Cycle regex engine
`Alt+i`	Toggle case-insensitive
`Alt+m`	Toggle multi-line
`Alt+s`	Toggle dot-matches-newline
`Alt+u`	Toggle unicode mode
`Alt+x`	Toggle extended mode
`?`	Show help
`Esc`	Quit

Engines

Engine	Features	Dependencies
Rust regex (default)	Fast, linear time, Unicode	Pure Rust
fancy-regex	+ lookaround, backreferences	Pure Rust
PCRE2	+ possessive quantifiers, recursion, conditionals	Requires libpcre2

Comparison

Feature	rgx	regex-tui	rexi	regex101.com
Real-time matching	Yes	Yes	Yes	Yes
Multiple engines	3	2	1	8
Capture group highlighting	Yes	No	No	Yes
Plain-English explanations	Yes	No	No	Yes
Regex flags toggle	Yes	Yes	No	Yes
Stdin pipe support	Yes	Yes	Yes	No
Offline / no browser	Yes	Yes	Yes	No
Cross-platform binary	Yes	Yes	No	N/A

Configuration

rgx looks for a config file at ~/.config/rgx/config.toml:

default_engine = "rust"  # "rust", "fancy", or "pcre2"

Contributing

See CONTRIBUTING.md for details.

License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE)
MIT License (LICENSE-MIT)

at your option.

rgx-cli 0.1.9

rgx