Rust入門者向けハンズオン #2 https://rust.connpass.com/event/43893/

cat.rs

extern crate getopts;

use std::env;
use std::io;
use std::io::BufReader;
use std::io::prelude::*;
use std::fs::File;
use getopts::Options;

fn main() {
    let args: Vec<String> = env::args().collect();

    let mut opts = Options::new();
    opts.optflag("n", "number", "number all output lines");
    let matches = match opts.parse(&args[1..]) {
        Ok(m) => m,
        Err(f) => panic!(f.to_string()),
    };
    let n = matches.opt_present("n");

    for (_, arg) in matches.free.iter().enumerate() {
        println!("{}",
                 match read_file(arg.clone(), n) {
                     Ok(content) => content,
                     Err(reason) => panic!(reason),
                 });
    }
}

fn read_file(filename: String, n: bool) -> Result<String, io::Error> {
    let file = File::open(filename)?;
    let br = BufReader::new(&file);
    let mut content = String::new();
    for (num, line) in br.lines().enumerate() {
        if n {
            content.push_str(&format!("   {} {}\n", num, line?));
        } else {
            content.push_str(&format!("{}\n", line?));
        }
    }
    Ok(content)
}

grep.rs

extern crate regex;

use std::env;
use std::io;
use std::io::BufReader;
use std::io::prelude::*;
use std::fs::File;
use regex::Regex;

fn main() {
    let args: Vec<String> = env::args().collect();
    if args.len() > 2 {
        let pattern = match Regex::new(&args[1]) {
            Ok(p) => p,
            Err(e) => panic!(e.to_string()),
        };

        for (_, arg) in args.iter().skip(2).enumerate() {
            filter_match(arg.clone(), &pattern).unwrap_or_else(|e| {
                panic!(e.to_string());
            });
        }
    }
}

fn filter_match(filename: String, pattern: &Regex) -> Result<(), io::Error> {
    let file = File::open(filename)?;
    let br = BufReader::new(&file);
    for (_, line) in br.lines().enumerate() {
        let s = line?;
        if pattern.is_match(&s) {
            println!("{}", s);
        }
    }
    Ok(())
}