Can someone help and explain the last part of this project "shuf" the skeleton is given need to finish it based on that ( read data from stdin)

103 Project 4 Reinventing Some Wheels Due: Friday, April 14th Recitation Synopsis In this project, you'll re-implement some standard unix utilities. In particular, you'll make clones (perhaps with some missing or different functionality) of wc, sort, uniq, shuf and tr. More about basic C++ data structures. Functions and arguments. A bit more about the unix shell