create

create 函数以只写模式打开文件。如果文件已存在，旧内容会被清除；否则，会创建一个新文件。

static LOREM_IPSUM: &str =
    "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
";

use std::fs::File;
use std::io::prelude::*;
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!("无法创建 {}: {}", display, why),
        Ok(file) => file,
    };

    // 将 `LOREM_IPSUM` 字符串写入 `file`，返回 `io::Result<()>`
    match file.write_all(LOREM_IPSUM.as_bytes()) {
        Err(why) => panic!("无法写入 {}: {}", display, why),
        Ok(_) => println!("成功写入 {}", display),
    }
}

以下是预期的成功输出：

$ rustc create.rs && ./create
successfully wrote to lorem_ipsum.txt

$ cat lorem_ipsum.txt
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

（与前面的示例类似，建议您在失败情况下测试此示例。）

OpenOptions 结构体可用于配置文件的打开方式。