Following the example here, I've created a sample & simple grep application in rust.
main.rs
use std::{env, process};
fn main() {
let args: Vec<String> = env::args().collect();
let config = rust1::Config::new(&args)
.unwrap_or_else(|err| {
eprintln!("parsing arguments failed: {err}");
process::exit(1);
});
if let Err(e) = rust1::run(config) {
eprintln!("application error {}", e);
process::exit(1);
}
}
lib.rs
use std::{env, fs};
use std::error::Error;
pub struct Config {
pub query: String,
pub file_path: String,
pub ignore_case: bool,
}
impl Config {
pub fn new(args: &[String]) -> Result<Config, &'static str> {
if args.len() != 3 {
return Err("invalid arguments amount");
}
let query = args[1].clone();
let file_path = args[2].clone();
let ignore_case = env::var("IGNORE_CASE").is_ok();
Ok(Config { query, file_path, ignore_case })
}
}
pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
let contents = fs::read_to_string(config.file_path)
.expect("should be able to read the file");
let results = if config.ignore_case {
search_case_insensitive(&config.query, &contents)
} else {
search(&config.query, &contents)
};
for line in results {
println!("{line}")
}
Ok(())
}
pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
let mut results = Vec::new();
for line in contents.lines() {
if line.contains(query) {
results.push(line);
}
}
results
}
pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
let query = query.to_lowercase();
let mut results = Vec::new();
for line in contents.lines() {
if line.to_lowercase().contains(&query) {
results.push(line);
}
}
results
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn case_sensitive() {
let query = "duct";
let contents = "\
Rust:
safe, fast, productive.
Pick three.";
assert_eq!(vec!["safe, fast, productive."], search(query, contents));
}
#[test]
fn case_insensitive() {
let query = "rUsT";
let contents = "\
Rust:
safe, fast, productive.
Pick three.
Trust me.";
assert_eq!(vec!["Rust:", "Trust me."], search_case_insensitive(query, contents));
}
}
