If you wish to monitor your Linux system in realtime, use dstat. Use a man dstat to see a list of possible options, since they are extensive and dstat can output system usage, memory usage, load times, network information, NFS, therman, VMWare, CPU, sendmail and MySQL usage, among others.
dstat -tamn -M topcpu
where -tamn stand for time, all, memory, network. Since dstat can do a lot of things, experiment with it and chose your output type that fits your needs.