entr ☆

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Description:
Run arbitrary commands when files change

Type: Formula | Latest Version: 5.7@0 | Tracked Since: Dec 17, 2025

Links: Homepage | formulae.brew.sh

Category: Developer tools

Tags: file-watcher developer-tools automation cli productivity

Install: brew install entr

About:
entr is a command-line utility that monitors a list of files for changes and executes an arbitrary command whenever a change is detected. It efficiently uses the kqueue or inotify APIs to provide instant file system event handling without polling. This tool is essential for developers seeking to automate build, test, or reload cycles in response to file modifications.

Key Features:

Efficient event-driven monitoring using kqueue and inotify
Non-bloated and focused on a single responsibility
Piping interface for easy integration with shell commands
Cross-platform support for BSD, Linux, and macOS

Use Cases:

Automatically re-run unit tests when source files change
Live-reload a web server or application during development
Trigger a build command upon file modification

Alternatives:

fswatch – fswatch is more feature-rich with regex filtering but is heavier than entr's minimalist approach.
inotify-tools – Linux-specific and relies on shell scripting loops, whereas entr is a single binary with cross-platform support.

License: ISC

Bottles available for: arm64_tahoe, arm64_sequoia, arm64_sonoma, arm64_ventura, sonoma, ventura, arm64_linux, x86_64_linux

Version History

Detected	Version	Rev	Change	Commit
Sep 13, 2025 1:37pm		0	VERSION_BUMP	43b7d2f0