Using watch to repeat comands

This tip shows you how to use watch to have commands run repeatedly. Make sure you have the sys-apps/procps package installed to make use of watch.

Whenever you have a long-running process (such as removing a complex directory tree or creating a large backup with tar), it is common to periodically check the progress of the task using ls, ps, grep, or a combination of these and other utilities. Instead of repeatedly executing these commands, you can have watch do it for you. For the most basic usage, just append your command to watch and run it. The screen will update every few seconds (2 by default), and rerun the command for you.

For example, if you're copying an ISO image that's about 650MB and you want to see if it's done, you could use a command similar to this one:

Code Listing 1

% watch ls -lh filename.iso

When the size stops increasing and it's around 650MB, you know the file copy operation has finished.

For more information on using watch, see man 1 watch.

From http://www.gentoo.org/news/en/gwn/20040126-newsletter.xml