如何检查路径是否存在？

Question

貌似是std::fs::PathExt和std::fs::metadata之间的选择，但还是建议选择后者，因为它更稳定。以下是我一直在使用的代码，因为它基于文档：

use std::fs;

pub fn path_exists(path: &str) -> bool {
    let metadata = try!(fs::metadata(path));
    assert!(metadata.is_file());
}

但是，由于某些奇怪的原因，let metadata = try!(fs::metadata(path)) 仍然需要函数返回 Result<T,E>，即使我只是想返回一个布尔值，如 assert!(metadata.is_file()) 所示。

尽管可能很快就会对此进行大量更改，但我如何绕过try!() 问题？

下面是相关的编译错误：

error[E0308]: mismatched types
 --> src/main.rs:4:20
  |
4 |     let metadata = try!(fs::metadata(path));
  |                    ^^^^^^^^^^^^^^^^^^^^^^^^ expected bool, found enum `std::result::Result`
  |
  = note: expected type `bool`
             found type `std::result::Result<_, _>`
  = note: this error originates in a macro outside of the current crate

error[E0308]: mismatched types
 --> src/main.rs:3:40
  |
3 |   pub fn path_exists(path: &str) -> bool {
  |  ________________________________________^
4 | |     let metadata = try!(fs::metadata(path));
5 | |     assert!(metadata.is_file());
6 | | }
  | |_^ expected (), found bool
  |
  = note: expected type `()`
             found type `bool`

Answer 1

请注意，很多时候您想对文件做某事，比如阅读它。在这些情况下，尝试打开它并处理Result 会更有意义。这消除了a race condition between "check to see if file exists" and "open file if it exists"。如果你真正关心的是它是否存在......

锈 1.5+

Path::exists... 存在：

use std::path::Path;

fn main() {
    println!("{}", Path::new("/etc/hosts").exists());
}

As mental points out, Path::exists 只是calls fs::metadata for you:

pub fn exists(&self) -> bool {
    fs::metadata(self).is_ok()
}

锈 1.0+

你可以检查fs::metadata方法是否成功：

use std::fs;

pub fn path_exists(path: &str) -> bool {
    fs::metadata(path).is_ok()
}

fn main() {
    println!("{}", path_exists("/etc/hosts"));
}

Answer 2

你可以使用std::path::Path::is_file:

use std::path::Path;

fn main() {
   let b = Path::new("file.txt").is_file();
   println!("{}", b);
}

https://doc.rust-lang.org/std/path/struct.Path.html#method.is_file