Source: An I/O Project: Building a Command Line Program
Rust's speed, safety, single binary output, and cross-platform support make it an ideal language
for creating command line tools, so for our project, we’ll make our own version of the classic
command line search tool grep (globally search a regular expression and print).
In the simplest use case, grep searches a specified file for a specified string. To do so, grep takes as its arguments a file path and a string. Then it reads the file, finds lines in that file that contain the string argument, and prints those lines.