dump all xml files from all virtual machines on a server in one line:
root@machine:~# for x in $(virsh list --all | tail -n +3 | awk '{print $2}'); do virsh dumpxml $x > "$x.xml"; done
root@machine:~#
for x in $(virsh list --all | tail -n +3 | awk '{print $2}'); do virsh dumpxml $x > "$x.xml"; done