This is a quick tip for not having to install a watcher that run tasks like build and test for every different project you have

The key to this is the Entr package. It’s purpose is to watch for file changes. Just like you would use npm run watch or whatever floats your goat.

First and foremost, install entr.

$ sudo apt install entr -y

Then, these things are best explained by a practical example.

$ ls **/*.go | entr -d sh -c 'go test -cover -v ./...'

What the above does: 1. List all go files in current directory level or lower and pass output to next command 2. Feed input from ls into entr * -d to check for new files * sh -c to run a shell command * 'go test -cover -v ./...' is just the command to run when something changes

For frontend projects I use something similar to this

$ ls frontend/**/*.* | entr -d npm run dev

where npm run dev will run tests and build things.

Entr is very flexible, I have used it to do the classic TDD workflow, having integration tests running in the background with curl and much more. Have fun with it!