Forgot to mention: This only works for

my=`/sbin/ifconfig usb0`

otherwise it would be true if *any* network adapter is RUNNING, as all lines are parsed by grep and it would find some line with RUNNING ;°)

So, this complete code must work:

#!/bin/sh

if `/sbin/ifconfig usb0 2>/dev/null | grep -q RUNNING`
then
echo "Ok"
else
echo "Not ok"
fi

if you replace usb0 by $1 as command line argument, you can use it for any network interface.