Watchexec: Run Commands Automatically When Files Change

TL;DR — Quick Summary

Watchexec watches for file changes and reruns commands automatically. Better than nodemon for any language — supports debouncing, filtering, and signals.

Watchexec is the universal file watcher. Change a file, it runs your command — any language, any tool. No configuration files, no plugins, just watchexec 'your command'.

Installation

# macOS
brew install watchexec

# Arch Linux
sudo pacman -S watchexec

# Cargo
cargo install watchexec-cli

# Ubuntu (via cargo or binary release)
cargo install watchexec-cli

Usage

# Watch everything, run on change
watchexec 'cargo test'
watchexec 'make build'
watchexec 'python main.py'

# Filter by extension
watchexec -e rs,toml 'cargo build'
watchexec -e py 'pytest'
watchexec -e ts,tsx 'npm test'
watchexec -e go 'go test ./...'

# Restart mode (kill and rerun — for servers)
watchexec -r 'npm start'
watchexec -r 'python app.py'
watchexec -r 'go run main.go'

# Ignore patterns
watchexec -i '*.log' -i 'node_modules' 'npm test'
watchexec -i 'target/' 'cargo build'

# Watch specific directory
watchexec -w src/ -w tests/ 'cargo test'

# Debounce (wait 500ms after last change)
watchexec --debounce 500 'make build'

# Clear screen before each run
watchexec -c 'cargo test'

# Shell mode (needed for pipes/redirects)
watchexec --shell=bash 'cargo test 2>&1 | head -20'

Comparison

Feature	Watchexec	nodemon	entr	inotifywait
Language	Any	Node.js	Any	Any
.gitignore	Yes	No	No	No
Restart mode	Yes	Yes	No	No
Debounce	Yes	Yes	No	No
Filter	ext/pattern	ext	manual	manual
Speed	Fast (Rust)	Moderate	Fast	Fast

Summary

Watchexec runs any command when files change — language-agnostic nodemon
Filter by extension, ignore patterns, respects .gitignore
Restart mode (-r) for servers: kills and restarts on change
Debouncing, screen clearing, signal handling built-in
Written in Rust for fast file system watching

Guide & Instructions

Estimated Time: 3m

Tools Needed:

Watchexec
Terminal

Install Watchexec

Install with brew install watchexec, cargo install watchexec-cli, or pacman -S watchexec.

Watch and run

Run watchexec 'cargo test' to re-run tests whenever any file changes.

Filter by extension

Use watchexec -e py 'pytest' to only watch .py files.

Restart mode

Use watchexec -r 'npm start' to kill and restart the server on file changes.

Ignore patterns

Use watchexec -i '*.log' -i 'tmp/*' 'make build' to ignore certain files.

Frequently Asked Questions

What is Watchexec?

Watchexec watches files for changes and re-executes a command when they change. It's language-agnostic — works with any build tool, test runner, or script. Think of it as a universal nodemon.

How is Watchexec different from nodemon?

nodemon is specific to Node.js. Watchexec works with any language and any command. It also supports debouncing, signal handling, process groups, and has better performance since it's written in Rust.

Can I filter which files to watch?

Yes, use -e to filter by extension (e.g., -e rs,toml), -i to ignore patterns, and -f to only watch specific patterns. Watchexec also respects .gitignore by default.

Does Watchexec restart or re-execute?

By default it re-executes (waits for completion, then reruns). With --restart/-r it kills the running process and starts a new one — useful for servers.