David Hancock

The watch command (Unix/Linux)

While attending a training class recently, I saw the instructor use the ‘watch’ command. What is does is clear the screen, echo the date/time, and execute the command you pass it. Very nice. For example:

watch ls /usr/local/pgsql/data/pg_xlog

lets you watch that directory for files to appear. If you need to pipe two commands together, put them together in quotes:

watch "ps auxww | grep postgres"

This is a very convenient replacement for how I USED to do this:

while (/bin/true)
do
    clear
    ps auxww | grep postgres
    sleep 2
done

If you want to use it, check out the man page; there are some cool features for highlighting changes, either per execution or cumulatively from the start.