On 1/13/21 3:42 PM, John Snow wrote: > On 1/13/21 4:48 AM, Stefan Hajnoczi wrote: >>> QEMU options are single dash with double dash accepted for >>> compatibility but >>> help and other docs have single dash so these (and below) should be >>> -trace. >>> (Also a bit less typing for otherwise already way too long command >>> lines.) >> Is this documented somewhere? >> >> I was under the impression that '-' is legacy syntax and '--' is the >> preferred syntax. There are examples of '--' on the QEMU man page.
Historically, uses of 'getopt_long()' support only double dash, while 'getopt_long_only()' support both single and double. While qemu does not use getopt_long_only() (because it rolls its own parser instead), it certainly tries to behave as if it does. Meanwhile, our other tools like qemu-img or qemu-storage-daemon use getopt_long(). I'm in favor of preferring the double-dash in documentation, even when single-dash works, especially for any option (like --trace) that is used for more tools than just qemu proper, because it makes for easier copy-paste between options that work for all tools in the qemu suite rather than just qemu. >> >> Let's reach agreement, document it, and then make the documentation >> consistent. >> >> Stefan > > My naive impression was that double-dash is the preferred idiom in > linuxdom in general for any multi-character option. > > We might hang on to single-dash for backwards compatibility, but I doubt > we want to enshrine that as our preferred way. > > Is there a reasoning I am unaware of? Continuing to document '-machine' instead of '--machine' for qemu is debatable because we don't support 'qemu-img --machine' or 'qemu-storage-daemon --machine'; but since 'qemu-img -trace' is an error while 'qemu-img --trace' works, I'm definitely in favor of preferring '--trace' everywhere in our docs. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
