Using Cisco devices sometimes it is needed to rewrite a part of configration for many interfaces. A router can sometimes have several hundred physical interfaces, if the nomeclature has been changed and one needs to change only 1 character or letter at the device it is useful to show only the needed part of the configurations. At IOS devices something like this can be done:

or with some regexp:

The same functionality presented at a NX-OS component, here using egrep

and just another example:

This way it is possible to parse and change hudge parts of the configuration in a quick and easy manner.