Hi all,
I find the Watch command very useful for monitoring the progress of large image files being copied over. However, the default output is in bytes and I would prefer (*much* prefer) to have it divided by 10^9 so I get to see gigabytes instead. What is the correct switch to use for this, please?
Thanks!

'man watch' ought to help you find out how to do it.

The watch command doesn't output bytes or gigabytes. In your case, the output probably comes from the command that it watches, such as dd. To help you, we would need to know how you use watch.

Commands that deal with bytes often have a -h/--human-readable option.

rsync (which is commonly used to copy large files) has this option, and also has -v/--verbose and -P/--progress options that may avoid the need for watch.

(If you're on the receiving end and using watch with ls, you will find that command also has a -h/--human-readable option.)

I'm using it for monitoring the progress of dd as it images a partition:
Even though the partition is 'only' 149Gb in size it's *really* hard to tell whether it's at 14.9Gb or 149Gb. I'd assumed like df for 'disk free' it would have the human-friendly -h switch but it seems it doesn't.

Your watch example makes no sense. For one, it's incomplete. It is missing 'dd' if you meant to include that and either an input option or an output option, depending on what you want to do with that image. Two, there is nothing to watch in a dd command if its command does not include the status option. 'df -h' is a better use of the watch command. dd not saying anything all the way to the prompt is a good thing but that's unnerving for a lot of people, lol.

Depending on its version, dd has progress status. Here's an example with the status option.
Because of your account name and your watch example, before you do carry out any more dd commands, you need to do the following:

• Put in 'man dd' in your terminal and hit return. Read carefully.
• Search for 'linux dd' with your favorite search engine and read carefully a few articles about dd from the results.

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You probably mean something like this:

That will review the size of imagefilename.img every second.

No need to use watch at all. Simply adfd 'status=progress' to the dd command.

This is not the watch that I know. The one I mean requires a command, not a filename.

I would do something like this:
or
or simply
(just noticed that I am not the first to suggest progress)

Okay, thanks guys. Seems I should forget about Watch and use status=progress with dd instead. But.... will the same problem arise again or will this genuinely provide a more readable output?

I should add there was no such 'progress' option with dd in the Linux Commands Bible I have (dated 2008) so it seems it's something that's been built into dd as an update at some time later.

The 'status=progress' option was added "recently", yes. I first learned about it here at linuxquestions.org.

I see from the posts after mine that you probably meant to have 'ls' instead of 'dd' in your 'watch' example. Now that makes more sense. 'watch' doesn't covert whatever command you've given it to something else. It just execute your commands and display the result at interval. That's all it does. So if you want to see a command printout in a human-readable form, you need to hit the man pages (or search online) of whatever command you're giving 'watch' to do and find that switch. It's often the '-h' switch but not always.

'watch' is a useful tool to have. Keep at it til you've figured it out.

GNU coreutils 8.24 (Jul 2015).