Recursive shasum generator for entries in filesystem

cargo.toml

[package]
name = "traverse"
version = "0.1.0"
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
sha2="0.10.2"
hex="0.3.1"

main.rs

use std::{env, fs};
use std::fs::File;
extern crate hex;
use std::path::{Path, PathBuf};
use std::io::Read;
use sha2::{Sha256, Digest};

fn main() -> Result<(), std::io::Error> {
    let args: Vec<String> = env::args().collect();

    let path : PathBuf;
    if args.len() == 1 {
        path = env::current_dir().unwrap();
    } else {
        path = Path::new(&args[1]).to_path_buf();
    }

    assert!(path.exists(), "Path does not exist!");
    assert!(path.is_dir(), "Path is not a directory!");
    
    println!("Traversing subdirs of {:?} ...", path);

    print_children(path)
}

fn print_children(path: PathBuf) -> Result<(), std::io::Error> {
    for entry in fs::read_dir(path)? {
        let entry = entry?;
        let path : PathBuf = entry.path();

        if path.is_dir() {
            print_children(path)?
        } else if path.is_file() {
            let mut f = File::open(path.as_path())?;
            let mut buf = Vec::<u8>::new();
            f.read_to_end(&mut buf)?;

            let mut hasher : Sha256 = Sha256::new();
            hasher.update(buf);
            let hash = hasher.finalize();

            println!("{}\t{:?}",hex::encode(&hash),path);
        }
    }

    Ok(())
}