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#![no_std]
#![no_main]
#![allow(clippy::println_empty_string)]
extern crate alloc;
#[macro_use]
extern crate user_lib;
const LF: u8 = 0x0au8;
const CR: u8 = 0x0du8;
const DL: u8 = 0x7fu8;
const BS: u8 = 0x08u8;
use alloc::string::String;
use user_lib::{exec, fork, getchar, waitpid};
// 教学目标：
// 实现一个最小用户态 shell，串联 getchar/fork/exec/waitpid 整条控制流。
#[unsafe(no_mangle)]
pub extern "C" fn main() -> i32 {
println!("Rust user shell");
let mut line: String = String::new(); // 记录着当前输入的命令
print!(">> ");
loop {
let c = getchar();
match c {
LF | CR => {
// 换行
println!();
if !line.is_empty() {
let pid = fork();
if pid == 0 {
// child process
// 子进程通过 exec 覆盖自身映像执行新程序。
if exec(line.as_str()) == -1 {
println!("Error when executing!");
return -4;
}
unreachable!();
} else {
// 父进程等待子进程完成，打印退出信息。
let mut exit_code: i32 = 0;
let exit_pid = waitpid(pid as isize, &mut exit_code);
assert_eq!(pid, exit_pid);
println!("Shell: Process {} exited with code {}", pid, exit_code);
}
line.clear();
}
print!(">> ");
}
BS | DL => {
// backspace
if !line.is_empty() {
print!("{}", BS as char);
print!(" ");
print!("{}", BS as char);
line.pop();
}
}
_ => {
print!("{}", c as char);
line.push(c as char);
}
}
}
}