Rust 实现一个简单的tail命令

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代码:

use std::{ fs::File, io::{self, BufRead, BufReader, Seek, SeekFrom}, thread::sleep, time::Duration, }; fn tail(file_path: &str, lines: usize) -> io::Result<()> { // 先打开文件，用 BufReader 读取全部行 let file_for_read = File::open(file_path)?; let reader = BufReader::new(file_for_read); let all_lines: Vec<String> = reader.lines().collect::<Result<_, _>>()?; // 打印最后 lines 行 let start = if all_lines.len() > lines { all_lines.len() - lines } else { 0 }; for line in &all_lines[start..] { println!("{}", line); } // 再打开一次文件用于监听尾部新增内容 let mut file_for_follow = File::open(file_path)?; let mut pos = file_for_follow.seek(SeekFrom::End(0))?; loop { let metadata = file_for_follow.metadata()?; let file_len = metadata.len(); if file_len > pos { file_for_follow.seek(SeekFrom::Start(pos))?; let new_reader = BufReader::new(&file_for_follow); let mut lines_iter = new_reader.lines(); while let Some(line) = lines_iter.next() { println!("{}", line?); } pos = file_for_follow.seek(SeekFrom::Current(0))?; } sleep(Duration::from_secs(1)); } } fn main() -> io::Result<()> { let args: Vec<String> = std::env::args().collect(); if args.len() < 2 { eprintln!("Usage: {} <file_path> [lines]", args[0]); std::process::exit(1); } let file_path = &args[1]; let lines = if args.len() > 2 { args[2].parse::<usize>().unwrap_or(10) } else { 10 }; tail(file_path, lines) } 

./target/release/tail_tool ./1.txt 5