On 10/21/2015 06:26 AM, Eric Blake wrote:
In this case migrate help is printed out. So far so good. However, you start writing this long migrate command (I bet you know the arguments there can get quite long), but then, at some point you need to print out the help. Something like this:
virsh # migrate --copy-storage-all --migrate-disks --help
In this specific case you just want to see the format that --migrate-disks accepts. So you append --help and expect help to be printed out. Well, it will not, because "--help" is taken as data to --migrate-disks.
But this is the behavior of ALL applications that use getopt_long():
$ ls --block-size --help ls: invalid --block-size argument '--help'
NACK; if you use --help in the position where it will be eaten as the argument to an incomplete long option, that's too bad for you, but we shouldn't special case it differently than getopt_long().
By the way, you CAN get in the habit of typing '--help --help' any time you want help but don't know if the first --help will just end up as filler to an incomplete option. It doesn't globally work, but happens to work for virsh. For 'virsh migrate --copy-storage-all --migrate-disks --help --help', we get help output (since we do all option parsing before any interpretation of the options, then make sure to interpret --help before any other option once --help is seen in an option position). Whereas with my ls example, 'ls --block-size --help --help' doesn't work; arguably something that could be patched in coreutils to be more user-friendly but not our problem here. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org