Gfrktyl

As part of my journey in learning the Rust programming language, I decided to make a miniature cat clone (catty) in it. The following is my code, which depends on clap for argument parsing (see below). It currently only supports concatenating 1 file with possibly numbered lines (-n/--number). I tried to be as close as possible to the actual cat program for this:

#[macro_use] extern crate clap;



use std::{io, error, env, fs::read_to_string, path::PathBuf, process};



fn main() {

    process::exit(

        if let Err(err) = cli(env::args().collect::<Vec<_>>()) {

            // CLI parsing errors

            if let Some(clap_err) = err.downcast_ref::<clap::Error>() {

                eprint!("{}", clap_err);

            } else {

                eprintln!("{}", err);

            }

            1

        } else {

            0

        }

    );

}



fn cli(cli_args: Vec<String>) -> Result<(), Box<error::Error>> {

    let matches = clap::App::new("catty")

        .version(crate_version!())

        .about("A minimal clone of the linux utility cat.")

        .arg(clap::Arg::with_name("FILE")

            .help("The file to concatenate to standard output")

            .required(true))

        .arg(clap::Arg::with_name("number")

            .short("n")

            .long("number")

            .help("Numbers all output lines"))

        .get_matches_from_safe(cli_args)?;



    let file_contents = get_file_contents(matches.value_of("FILE").unwrap())?;

    let file_contents: Vec<&str> = file_contents.split("n").collect();



    let number_lines = matches.is_present("number");



    for (i, line) in file_contents.iter().enumerate() {

        let formatted_line = if number_lines {

            format!("{:>6}  {}", i + 1, line)

        } else {

            line.to_string()

        };



        if i == file_contents.len() - 1 && line.len() > 0 {

            print!("{}", formatted_line);

        } else if !(i == file_contents.len() - 1 && line.len() == 0) {

            println!("{}", formatted_line);

        }

    }



    Ok(())

}



fn get_file_contents(passed_argument: &str) -> Result<String, Box<error::Error>> {

    let mut resolved_path = PathBuf::from(passed_argument);



    if !resolved_path.exists() || !resolved_path.is_file() {

        resolved_path = PathBuf::from(env::current_dir()?);

        resolved_path.push(passed_argument);



        if !resolved_path.exists() || !resolved_path.is_file() {

            return Err(io::Error::new(io::ErrorKind::NotFound, "The passed file is either not a file or does not exist!").into());

        }

    }



    Ok(read_to_string(resolved_path)?)

}

My Cargo.toml is as follows:

[package]

name = "catty"

version = "0.1.0"

authors = ["My Name <my@email.com>"]



[dependencies]



[dependencies.clap]

version = "2.32"

default-features = false

features = ["suggestions"]

Here is what I want to know from this code review:

1. Is my code idiomatic rust (i.e good error handling, not overly verbose, etc)?


2. Is my code performant or can it be improved in some way?

4: use std::{env, error, fs::read_to_string, io, path::PathBuf, process};

Just a personal taste, but I would do

use std::{env, error, io, process};

use std::fs::read_to_string;

use std::path::PathBuf;

Yes, nested includes are nice and easy, but hard to extend. It's up to you.

35: let file_contents: Vec<&str> = file_contents.split('n').collect();

I would suggest using lines instead.

Also, you can omit &str or change the line completly.

Either

let file_contents: Vec<_> = file_contents.lines().collect();

or

let file_contents = file_contents.lines().collect::<Vec<_>>();

46/48: line.len() > 0 / line.len() == 0

Replace that by !line.is_empty() and line.is_empty().

60: resolved_path = PathBuf::from(env::current_dir()?);

Remove PathBuf::from completly, because current_dir is already a PathBuf