Rust系统编程之文件IO

1. 读取文件

以读写、追加的形式读取文件并返回byte vector

use std::fs::OpenOptions;
use std::io::prelude::*;
use std::path::Path;

fn read_my_file(path: &Path) -> std::io::Result<Vec<u8>> {
    let mut f = OpenOptions::new().read(true).write(true).append(true).open(path)?;
    let mut vec:Vec<u8> = Vec::new();
    f.read_to_end(&mut vec)?;
    Ok(vec)
}

fn main() {
    // 创建指向所需的文件的路径
    let path = Path::new("hello.txt");
    let display = path.display();

    match read_my_file(path) {
        Ok(s) => println!("file data is: {:?}", s),
        Err(why) => println!("{} contains:\n{}", display, why),
    }

    // `file` 离开作用域，并且 `hello.txt` 文件将被关闭。
}

2. 创建文件

只写方式打开文件，如果文件存在清空，不存在创建。

static LOREM_IPSUM: &'static str =
"Hello World";

use std::io::prelude::*;
use std::fs::File;
use std::path::Path;

fn main() {
    let path = Path::new("lorem_ipsum.txt");
    let display = path.display();

    // 以只写模式打开文件，返回 `io::Result<File>`
    let mut file = match File::create(&path) {
        Err(why) => panic!("couldn't create {}: {:?}", display, why),
        Ok(file) => file,
    };

    // 将 `LOREM_IPSUM` 字符串写进 `file`，返回 `io::Result<()>`
    match file.write_all(LOREM_IPSUM.as_bytes()) {
        Err(why) => {
            panic!("couldn't write to {}: {:?}", display, why)
        },
        Ok(_) => println!("successfully wrote to {}", display),
    }
}