rust unwrap

https://zhuanlan.zhihu.com/p/109242831

fn main() {
    let path = "/tmp/dat";
    println!("{}", read_file(path));
}

fn read_file(path: &str) -> String {
    std::fs::read_to_string(path).unwrap()
}

   Compiling hello_world v0.1.0 (/data2/rust/unwrap)
    Finished dev [unoptimized + debuginfo] target(s) in 0.47s
[root@bogon unwrap]# cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/hello_world`
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }', src/main.rs:7:43
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

fn main() {
    let path = "/tmp/dat";  //文件路径
    match read_file(path) { //判断方法结果
        Ok(file) => { println!("{}", file) } //OK 代表读取到文件内容，正确打印文件内容
        Err(e) => { println!("{} {}", path, e) } //Err代表结果不存在，打印错误结果
    }
}

fn read_file(path: &str) -> Result<String,std::io::Error> { //Result作为结果返回值
    std::fs::read_to_string(path) //读取文件内容
}

[root@bogon unwrap2]# cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/hello_world`
/tmp/dat No such file or directory (os error 2)

[root@bogon unwrap2]# touch /tmp/dat
[root@bogon unwrap2]# cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/hello_world`

[root@bogon unwrap2]# echo 'test unwrap' >> /tmp/dat
[root@bogon unwrap2]# cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/hello_world`
test unwrap

[root@bogon unwrap2]#