Rust实现一个简单的文本过滤命令行工具

创建项目

创建一个名称为minigrep的项目

cargo new minigrep

编写代码

测试文件文件

Youth is not a time of life; it is a state of mind; 
it is not a matter of rosy cheeks, red lips and supple knees; 
it is a matter of the will, a quality of the imagination, a vigor of the emotions; 
it is the freshness of the deep springs of life.

main.rs文件内容

use std::env;
use std::process;

use minigrep::Config;

fn main() {
    let args: Vec<String> = env::args().collect();  // 获取用户的输入

    let config = Config::build(&args).unwrap_or_else(|err| {
        eprintln!("Problem parsing arguments: {err}");  // 输出错误到标准错误输出
        process::exit(1);  // 退出程序，返回码为1
    });

    if let Err(e) = minigrep::run(config) {  // 匹配返回的错误
        eprintln!("Application error: {e}");  // 输出错误到标准错误输出
        process::exit(1);
    }
    
}

lib.rs内容

use std::error::Error;
use std::fs;
use std::env;

pub struct Config {
  pub query: String,   // 搜索的字符串
  pub file_path: String,  // 打开的文件
  pub ignore_case: bool,  // 是否开启大小写敏感
}

impl Config {
  pub fn build(args: &[String]) -> Result<Config, &'static str> {
      if args.len() < 3 {
          return Err("not enough arguments");  // 参数小于三个报错
      }

      let query = args[1].clone();  // 获取搜索的字符串
      let file_path = args[2].clone();   // 获取要打开的文件
      let ignore_case = env::var("IGNORE_CASE").is_ok();  // 从环境变量中获取是否开启大小写敏感， is_ok有值返回true，没有返回false
  
      Ok(Config {query, file_path, ignore_case})
  }
}

pub fn run(config: Config) -> Result<(), Box<dyn Error>> {  // 使用特征对象返回错误
  let contents = fs::read_to_string(config.file_path)?;

  let results = if config.ignore_case {
    search_case_insensitive(&config.query, &contents)
  } else {
    search(&config.query, &contents)
  };

  for line in results {
    println!("{line}");
  }

  Ok(())
}

// 大小写敏感的搜索函数
pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
  let mut results = Vec::new();
  for line in contents.lines() {
    if line.contains(query) {
      results.push(line);
    }
  }

  results
}

// 大小写不敏感的搜索函数
pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
  let query = query.to_lowercase();
  let mut results = Vec::new();

  for line in contents.lines() {
    if line.to_lowercase().contains(&query) {
      results.push(line);
    }
  }

  results
}

// 编写一个测试用例

#[cfg(test)]
mod tests {
  use super::*;

  #[test]
  fn one_result() {
    let query = "safe";
    let contents = "\
Rust:
safe, fast, productive.
Pick three.";

    assert_eq!(vec!["safe, fast, productive."], search(query, contents));
  }

  #[test]
  fn case_sensitive() {
      let query = "duct";
      let contents = "\
Rust:
safe, fast, productive.
Pick three.
Duct tape.";

      assert_eq!(vec!["safe, fast, productive."], search(query, contents));
  }

  #[test]
  fn case_insensitive() {
      let query = "rUsT";
      let contents = "\
Rust:
safe, fast, productive.
Pick three.
Trust me.";

      assert_eq!(
          vec!["Rust:", "Trust me."],
          search_case_insensitive(query, contents)
      );
  }
}

项目目录结构

测试

大小写敏感

➜  minigrep git:(master) ✗ cargo run -- Deep test.txt 
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.02s
     Running `target/debug/minigrep Deep test.txt

大小写不敏感

➜  minigrep git:(master) ✗ IGNORE_CASE=1 cargo run -- Deep test.txt
   Compiling minigrep v0.1.0 (/Users/tang/rust_project/minigrep)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.85s
     Running `target/debug/minigrep Deep test.txt`
it is the freshness of the deep springs of life.