OS X Bash, 'watch' command

Question

I'm looking for the best way to duplicate the Linux 'watch' command on Mac OS X. I'd like to run a command every few seconds to pattern match on the contents of an output file using 'tail' and 'sed'.

What's my best option on a Mac, and can it be done without downloading software?

Answer 1

With Homebrew installed:

brew install watch

Answer 2

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