ifconfig command not found

I’ve just installed CentOS7 as a virtual machine on my mac (osx10.9.3 + virtualbox) .Running ifconfig returns command not found. Also running sudo /sbin/ifconfig returns commmand not found. I am root. The output of
echo $PATH is as below.

clear full-screen in script and get the previous prompts after exiting script

Today I was using glance tool in my office to monitor CPU utilization.When I run glance from terminal ,the command clears the screen and after all the work when I quit back to the terminal,the previous prompts are still there on my screen.I mean that I can see all the previous lines.My question is how is this effect of clearing screen achieved.If they had used command like clear,It should have cleared the whole screen,how did they manage to get back all the previous prompts ? I want to implement the same feature for some of my scripts.