Concatenate files

cat.rs

use std::{fs::{self, File}, io};

fn main() -> io::Result<()> {
    // Create the output file
    let mut output = File::create("catted")?;

    // Find all files starting with "input_"
    let mut input_files = fs::read_dir(".")?
        .filter_map(|entry| {
            let entry = entry.ok()?;
            let path = entry.path();
            if path.is_file() && path.file_name()?.to_str()?.starts_with("input_") {
                Some(path)
            } else {
                None
            }
        })
        .collect::<Vec<_>>();

    // Sort the file paths alphabetically
    input_files.sort();

    if input_files.is_empty() {
        eprintln!("No input files found starting with 'input_'.");
        return Ok(());
    }

    // Process and concatenate each input file
    for input_path in input_files {
        eprintln!("Processing file: {}", input_path.display());
        let mut input = File::open(&input_path)?;
        io::copy(&mut input, &mut output)?;
    }

    eprintln!("All input files concatenated into 'catted'.");
    Ok(())
}