How can I use a Bash script to determine if Virtualbox vm is running?

el_pedro · 11-10-2011, 08:05 AM

Hi,

I'm very new to bash scripts (and linux in general) but am trying to run a script on a host to determine if any VirtualBox virtualmachines are running.

The relevant part of the script is:

Code:

if [ 'sudo -u virtualboxuser VBoxManage list runningvms | wc -l' != "0" ]
    then
        echo "VirtualMachine is running" >> $logfile
        echo $(sudo -u virtualboxuser VBoxManage list runningvms | wc -l) >> $logfile
fi

Unfortunately, I always seem to enter the 'if' statement even if no virtual machines are running. I'm piping the output to a logfile, and looking at my logfile I can see that the result of the line

Code:

echo $(sudo -u virtualboxuser VBoxManage list runningvms | wc -l) >> $logfile

is 0.

Please can anyone tell me why the 'if' statement is still being executed? Or is there a better way to determine if any virtualmachines are running?

catkin · 11-10-2011, 08:18 AM

The problem is in

Code:

if [ 'sudo -u virtualboxuser VBoxManage list runningvms | wc -l' != "0" ]

The single quotes make the intended command pipeline a string so it is never equal to string "0".

If you change it to the form you use later, it should work

Code:

if [ $( sudo -u virtualboxuser VBoxManage list runningvms | wc -l ) != "0" ]

Purists would say it is a numeric comparison so should be -eq 0, not = "0".

Purists would say that numeric tests should go in (( ... )) numeric tests not in [ ... ] tests in which case the comparison operator would have to be != or, more naturally, >.

More here.

el_pedro · 11-10-2011, 08:21 AM

Thanks v much catkin.

catkin · 11-10-2011, 08:24 AM

AFAIK the VBoxManage list runningvms command only lists VMs being run by the user that issued the command, not all VMs on the local system.

Juako · 11-10-2011, 08:31 AM

If you are in Bash you can use this too:

Code:

echo "Virtual machine is $([[ ! $(VBoxManage list runningvms) ]] && echo "not ")running" >> $logfile