Re: [Qemu-devel] question about qemu-monitor-event result redirecting to a file

[John Snow]

On 2/26/19 6:51 AM, Zhan Adlun wrote:
> Dear Sir:
>       Sorry to bother you. I use dirty bitmap to do backup in KVM. I could 
> get output from the terminal when I use the command ' virsh 
> qemu-monitor-event DOMAIN --timestamp --loop', but when using ' virsh 
> qemu-monitor-event DOMAIN --timestamp --loop > /file ' to redirect the output 
> to a file, I got nothing both from the terminal and the file. My os version 
> is 'Distributor ID: Ubuntu   Description: Ubuntu 12.04 LTS   Release: 12.04   
> Codename: precise,Linux version 4.1.0-generic (address@hidden) (gcc version 
> 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #1 SMP Wed Nov 9 02:04:23 CST 2016'. 
> KVM version is 'QEMU emulator version 2.7.1(Debian 1:2.7+dfsg-3)'. Hoping for 
> you reply. Thanks!
> 

Hi, I'm not experienced with how virsh manages its IO streams. The
behavior that you see no output in the file OR the console is strange to
me, though.

If you are using bash (or a bash-alike), try
`virsh ...etc... > file.txt 2>&1`
which should really truly output everything to file, but you may have to
wait for stdout flushes to see it, or you can try:
`virsh ...etc... 2>&2 | tee file.txt`
which will hopefully let you monitor the output as it occurs.

Maybe someone else on list with more knowledge of virsh's behaviors can
comment.

--js