Re: [Qemu-block] interactive qemu-img

[Eric Blake]

On 07/30/2018 02:54 PM, Nir Soffer wrote:

> > > $ qemu-img
> > > qemu-img: Not enough arguments
> > > Try 'qemu-img --help' for more information
>
>
> This is not user friendly, but unfortunately very common.
> It can be improved by treating no arguments as --help, like git.

I somewhat disagree that git is a good example.  If '--help' occupies 
more than about 25 lines (a screenful on some default terminal sizes), 
the mere fact that you have to scroll to read it makes it less helpful 
than a 2-liner statement that lets you know "I couldn't do anything 
useful with your botched command line, please read the documentation and 
try again".  'git' behaving as 'git --help' outputs 42 lines, which 
fails my 'one screenful' test; and 'qemu-img --help' at 104 lines is 
definitely too verbose to be the default behavior when --help is not given.

/me Wow - I can't believe I'm actually about to use this as an example, but:

'cvs' and 'cvs --help' is just 13 lines (except to stderr, when it 
should have been stdout), and gives enough hints on how to get more 
specific help on a particular topic.  Great for the plain 'cvs' case; a 
bit more debatable on 'cvs --help' (the fact that you have to ask for 
help twice: once for the summary, again for the specific help, gets 
tedious).

At any rate, getting command-line tools to have user-friendly behavior 
when insufficient arguments are supplied is an artform, and you'll find 
lots of bikeshed colors out there.

And regardless of any opinions I've expressed above, this thread does 
point out that 104 lines for 'qemu-img --help' is long, and anything we 
can do to make that easier to digest may still be worthwhile.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org