Why standard I/O cannot be executed in order correctly

[zyb]

//This is my code
fn stdio_demo() -> io::Result<()>{

    let mut s:String = String::new();

    //标准输入
    let s_tips:String = String::from("请输入：");
    io::stdout().write(s_tips.as_bytes())?;
    io::stdin().read_line(&mut s)?;

    //标准输出
    s = format!("{}{}{}", "输出：", s, "\n");
    io::stdout().write(s.as_bytes())?;

    Ok(())

}

I entered "test" in the terminal, but the displayed results did not execute normally

//This is the result of execution
test
请输入：输出：test
![image|599x284](upload://63IFjCNJIxZhA7SH4bZ6acQaQW8.png)

Online waiting for guidance from the boss😂

[H2CO3]

What did yo expect and what happened instead?

---

In any case, there are at least 2 things wrong with your code:

• write() isn't guaranteed to write everything; that'd be write_all(). Please read the documentation; this is clearly stated there.
• Standard I/O is buffered by default. You won't see anything printed until a newline is encountered or you explicitly flush().

By the way, is there a reason you aren't using print!() for output? It doesn't seem like you need to call the Write impl on Stdout directly.

[zyb]

@H2CO3

flush()

Thanks for your correction. The problem has been solved with flush()

[kornel]

Never use write(). This function is an awful trap, by design. Always use write_all() instead.