On Wed, Jan 20, 2021 at 10:25:25AM +0200, Dov Murik wrote:
Hi John,
On 19/01/2021 22:02, John Snow wrote:
On 1/17/21 2:27 AM, Dov Murik wrote:
Detect whether qmp-shell's standard input is not a TTY; in such case,
assume a non-interactive mode, which suppresses the welcome banner and
the "(QEMU)" prompt. This allows for easier consumption of
qmp-shell's
output in scripts.
Example usage before this change:
$ printf "query-status\nquery-kvm\n" | sudo
scripts/qmp/qmp-shell qmp-unix-sock
Welcome to the QMP low-level shell!
Connected to QEMU 5.1.50
(QEMU) {"return": {"status": "running", "singlestep": false,
"running": true}}
(QEMU) {"return": {"enabled": true, "present": true}}
(QEMU)
Example usage after this change:
$ printf "query-status\nquery-kvm\n" | sudo
scripts/qmp/qmp-shell qmp-unix-sock
{"return": {"status": "running", "singlestep": false,
"running": true}}
{"return": {"enabled": true, "present": true}}
Signed-off-by: Dov Murik <dovmurik@linux.vnet.ibm.com>
Hiya! I've been taking lead on modernizing a lot of our python
infrastructure, including our QMP library and qmp-shell.
(Sorry, not in MAINTAINERS yet; but I am in the process of moving these
scripts and tools over to ./python/qemu/qmp.)
Thanks for this effort.
This change makes me nervous, because qmp-shell is not traditionally a
component we've thought of as needing to preserve backwards-compatible
behavior. Using it as a script meant to be consumed in a headless
fashion runs a bit counter to that assumption.
I'd be less nervous if the syntax of qmp-shell was something that was
well thought-out and rigorously tested, but it's a hodge-podge of
whatever people needed at the moment. I am *very* reluctant to cement
it.
Yes, I understand your choice.
Are you trying to leverage the qmp.py library from bash?
Yes, I want to send a few QMP commands and record their output. If I
use
socat to the unix-socket I need to serialize the JSON request myself, so
using qmp-shell saves me that; also not sure if there's any
negotiation done
at the beginning by qmp-shell.
There is a handshake, but it is just a single json message.
See docs/interop/qmp-intro.txt and qmp-spec.txt for guidance.
Is there an easier way to script qmp commands, short of writing my own
python program which uses the qmp.py library?
Yes, writing your own python program is probably best. Doing anything
complex is shell is almost always a mistake, as it is a very crude
and poor language compared to something like managing QEMU/QMP.
Note that I don't believe that we've declared qmp.py to be a long
term stable interface for users outside of QEMU either. An alternative
is to just use the python sockets APIs directly to speak to QEMU/QMP