OS X Bash, 'watch' command

With Homebrew installed:

brew install watch

You can emulate the basic functionality with the shell loop:

while :; do clear; your_command; sleep 2; done

That will loop forever, clear the screen, run your command, and wait two seconds - the basic watch your_command implementation.

You can take this a step further and create a watch.sh script that can accept your_command and sleep_duration as parameters:

#!/bin/bash
# usage: watch.sh <your_command> <sleep_duration>

while :; 
  do 
  clear
  date
  $1
  sleep $2
done

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