[CentOS] Network Utilization

> I'm attempting to create a script that will indicate the % utilization
> of a network interface. I need this to export a one shot output that can
> be called by nagios.
>
> I've tried the following tools but I was unable to find a way to output
> just the utilization, and just one time: bmon, iftop, ifstat, bwm,
> dstat, rrdtool, iptraf.
>
>   

ntop ?