name: entr description: Run arbitrary commands when files change. Useful for watching files and triggering builds or tests.

entr (Event Notify Test Runner)

A utility for running arbitrary commands when files change.

Usage

entr takes a list of filenames from standard input and executes the utility specified as the first argument.

Syntax

<file_listing_command> | entr <utility> [arguments]

Options

• -c: Clear the screen before invoking the utility.
• -r: Reload a persistent child process (e.g., a server).
• -s: Evaluate the first argument using the interpreter specified by SHELL.

Examples

Rebuild project when sources change:

find src/ -name "*.c" | entr make

Run tests when JS files change:

git ls-files | grep '\.js$' | entr npm test

Auto-reload a Node server:

ls *.js | entr -r node app.js

Agent Notes

entr blocks the terminal. When using it as an agent:

1. Use process tool to run it in the background if you need to do other things.
2. Or use it for a quick "watch mode" session where you intend to monitor output for a while.