Command-Line Rust

Chapter 12. Fortunate Son

Now I laugh and make a fortune / Off the same ones that I tortured

They Might Be Giants, “Kiss Me, Son of God” (1988)

In this chapter, you will create a Rust version of the fortune program that will print a randomly selected aphorism or bit of trivia or interesting ASCII art¹ from a database of text files. The program gets its name from a fortune cookie, a crisp cookie that contains a small piece of paper printed with a short bit of text that might be a fortune like “You will take a trip soon” or maybe a short joke or saying. When I was first learning to use a Unix terminal in my undergraduate days,² a successful login would often include the output from fortune.

You will learn how to do the following:

• Use the Path and PathBuf structs to represent system paths

• Parse records of text spanning multiple lines from a file

• Use randomness and control it with seeds

• Use the OsStr and OsString types to represent filenames

How fortune Works

I will start by describing how fortune works so you will have an idea of what your version will need to do. You may first need to install the program,³ as it is not often present by default on most systems. Here’s a bit of the manual page, which you can read with man fortune:

NAME fortune - print a random, hopefully interesting, adage SYNOPSIS fortune [-acefilosuw] [-n length] [ -m pattern] [[n%] file/dir/all] DESCRIPTION When fortune is run with no arguments it prints out a random epigram. Epigrams are divided ...