You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: cat.rs
    path of file: ./repos/rCore-Tutorial-v3/user/src/bin
    
    the code of the file until where you have to start completion: #![no_std]
#![no_main]

#[macro_use]
extern crate user_lib;
extern crate alloc;

use user_lib::{close, open, read, OpenFlags};

#[no_mangle]
pub fn main(argc: usize, argv: &[&str]) -> i32 {
    println!("argc = {}", argc);
    for (i, arg) in argv.iter().enumerate() {
        println!("argv[{}] = {}", i, arg);
    }
    assert!(argc == 2);
    let 
    
pub fn main(argc: usize, argv: &[&str]) -> i32 {
    println!("argc = {}", argc);
    for (i, arg) in argv.iter().enumerate() {
        println!("argv[{}] = {}", i, arg);
    }
    assert!(argc == 2);
    let fd = open(argv[1], OpenFlags::RDONLY);
    if fd == -1 {
        panic!("Error occurred when opening file");
    }
    let fd = fd as usize;
    let mut buf = [0u8; 256];
    loop {
        let size = read(fd, &mut buf) as usize;
        if size == 0 {
            break;
        }
        print!("{}", core::str::from_utf8(&buf[..size]).unwrap());
    }
    close(fd);
    0
}