Chapter 2. Test for Echo
By the time you get this note / We’ll no longer be alive / We’ll have all gone up in smoke / There’ll be no way to reply
They Might Be Giants, “By the Time You Get This” (2018)
In Chapter 1, you wrote three programs—
false—that take no arguments and always produce the same output.
In this chapter, I’ll show you how to use arguments from the command line to change the behavior of the program at runtime.
The challenge program you’ll write is a clone of
echo, which will print its arguments on the command line, optionally terminated with a newline.
In this chapter, you’ll learn how to do the following:
Process command-line arguments with the
Use Rust types like strings, vectors, slices, and the unit type
Use expressions like
Optionto represent an optional value
Handle errors using the
Understand the difference between stack and heap memory
Test for text that is printed to
How echo Works
In each chapter, you will be writing a Rust version of an existing command-line tool, so I will begin each chapter by describing how the tool works so that you understand what you’ll be creating.
The features I describe are also the substance of the test suite I provide.
For this challenge, you will create a Rust version of the
echo program, which is blissfully simple.
echo will print its arguments to
$ echo Hello Hello
I’m using the ...
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