There are many ways to achieve this, but this is probably the simplest since you most likely already have all the necessary components installed.
On Ubuntu it's the "
shuf" command from "
coreutils" package. It's original purpose is to shuffle the lines passed to it, or as its description says: "write a random permutation of the input lines to standard output". However, with one of the arguments you can limit the number of lines it returns, so if all you need is a single line from a given text file, juts run:
$ shuf –n 1 list.txt
shuf to print only one random line from file list.txt