entr

Run arbitrary commands when files change. Useful for watching files and triggering builds or tests.

Security Scan

This is an instruction-only skill that documents how to use the existing 'entr' file-watching utility; its instructions and requirements are consistent with its stated purpose, but it enables running arbitrary shell commands so exercise normal operational caution.

Purpose & Capability

The name/description match the SKILL.md content: this skill documents usage of the 'entr' utility to run commands on file changes. It requests no binaries, env vars, or config paths and does not try to perform unrelated actions.

Instruction Scope

Instructions stay on-topic (examples show piping file lists into entr and options). However, by design the tool runs arbitrary utilities/commands when files change — that capability is powerful and could be harmful if the commands provided are unsafe. The SKILL.md also suggests using a 'process' tool to run it in background (agent-specific advice) but does not instruct reading unrelated files or secrets.

Install Mechanism

No install spec—this is instruction-only, so nothing is downloaded or written by the skill itself (lowest install risk).

Credentials

No environment variables or credentials are requested. The only environment reference is that the '-s' option evaluates the command under SHELL, which is expected and proportional.

Persistence & Privilege

always:false (no forced inclusion). disable-model-invocation is false (agent may invoke autonomously), which is the platform default; there is no attempt to modify other skills or system configs.

Assessment

This skill is just documentation for using the external 'entr' program — it does not install anything. Before using or allowing an agent to invoke it: (1) ensure you have the official 'entr' package installed from your OS package manager or trusted source; (2) review and control the exact commands you will run under entr — it will execute arbitrary shell commands on file changes and those commands can be destructive; (3) avoid running watched commands as a privileged user, and prefer testing in a sandboxed or non-production directory first; (4) if you allow autonomous agent invocation, restrict the agent's ability to run destructive commands or limit it to safe wrappers that validate inputs.

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.