Is there a command like "watch" or "inotifywait" on the Mac?

This is just to mention entr as an alternative on OSX to run arbitrary commands when files change. I find it simple and useful.

• brew install entr on macos
• apt install entr on Debian/Ubuntu

I ended up doing this for macOS. I'm sure this is terrible in many ways:

#!/bin/sh
# watchAndRun
if [ $# -ne 2 ]; then
    echo "Use like this:"
    echo "   $0 filename-to-watch command-to-run"
    exit 1
fi
if which fswatch >/dev/null; then
    echo "Watching $1 and will run $2"
    while true; do fswatch --one-event $1 >/dev/null && $2; done
else
    echo "You might need to run: brew install fswatch"
fi

If you want to use NodeJS, you can use a package called chokidar (or chokidar-cli actually) for the watching and then use rsync (included with Mac):

Rsync command:

$ rsync -avz --exclude 'some-file' --exclude 'some-dir' './' '/my/destination'

Chokidar cli (installed globally via npm):

chokidar \"**/*\" -c \"your-rsync-command-above\"

sudo fs_usage -f filesys | grep "interesting thing" ?

I can wholeheartedly recommend using watchexec. Built in Rust and It Just Works™ no matter which platform you're on! Straightforward CLI options as well.

Here's a simple single line alternative for users who don't have the watch command who want to execute a command every 3 seconds:

while :; do your-command; sleep 3; done

It's an infinite loop that is basically the same as doing the following:

watch -n3 your-command