Rust 中是否存在文件锁定

对于当代 rust 病(1.8+)，应使用fs2 crate.它是一个跨平台库，提供一些标准库中找不到的文件系统功能，包括文件锁定.

fs2的文件锁定函数在UNIX上内部使用flock(2)，在Windows上内部使用LockFileEx.

例子:

//! This program tries to lock a file, sleeps for N seconds, and then unlocks the file.

// cargo-deps: fs2
extern crate fs2;

use fs2::FileExt;
use std::io::Result;
use std::env::args;
use std::fs::File;
use std::time::Duration;
use std::thread::sleep;

fn main() {
    run().unwrap();
}

fn run() -> Result<()> {
    let sleep_seconds = args().nth(1).and_then(|arg| arg.parse().ok()).unwrap_or(0);
    let sleep_duration = Duration::from_secs(sleep_seconds);

    let file = File::open("file.lock")?;

    println!("{}: Preparing to lock file.", sleep_seconds);
    file.lock_exclusive()?; // block until this process can lock the file
    println!("{}: Obtained lock.", sleep_seconds);

    sleep(sleep_duration);

    println!("{}: Sleep completed", sleep_seconds);
    file.unlock()?;
    println!("{}: Released lock, returning", sleep_seconds);

    Ok(())
}

我们可以看到，这两个进程是按顺序排列的，等待文件锁定.

$ ./a 4 & ./a 1
[1] 14894
4: Preparing to lock file.
4: Obtained lock.
1: Preparing to lock file.
4: Sleep completed
4: Released lock, returning
1: Obtained lock.
1: Sleep completed
1: Released lock, returning
[1]+  Done                    ./a 4