Ex 1. Write a script that stores the time it takes a command (your choice of command)
to run in three variables, real, user, and system, corresponding to the three
default times that time prints.

Ex 2.What is wrong with if [ $var=x ]? What should it be? Why does it give the result it does?

Ex 3. Write a function, valid_square(), that returns successfully if its sole argument is a

valid SAN chessboard square or fails if it is not. Write a function to test that it works.