OpenNebula

Instead of parsing programs output in bash script better idea is to use libvirt and xen api. For example /var/tmp/one/vmm/kvm/poll could be written in that way:

#!/bin/python
import sys

import libvirt

URI = 'qemu:///system'

states = {
        libvirt.VIR_DOMAIN_RUNNING : 'a',
        libvirt.VIR_DOMAIN_BLOCKED : 'a',
        libvirt.VIR_DOMAIN_SHUTDOWN : 'a',
        libvirt.VIR_DOMAIN_SHUTOFF : 'a',
        libvirt.VIR_DOMAIN_PAUSED : 'p',
        libvirt.VIR_DOMAIN_CRASHED : 'c',
}

conn = libvirt.openReadOnly(URI)
if conn == None:
    sys.exit(1)
try:
    domain = conn.lookupByID(int(sys.argv[1]))
    state, max_mem, mem, nr_cpus, time_cpu = domain.info()
    state = states.get(state, 'u')
    print 'STATE=%s MEMORY=%d' % (state, mem)
except:
    print 'STATE=d'

I'm using python bindings here, but of course ruby-bindings also exists.