用 Rust 打造命令行利器：从零到一实现 mini-grep
- 寻月隐君
- 发布于 2025-06-02 10:20
- 阅读 1209
用Rust打造命令行利器：从零到一实现mini-grep在开发中，命令行工具以其高效和灵活深受开发者喜爱。本文通过一个Rust实现的mini-grep项目，带你从零开始学习如何构建一个功能强大的命令行程序。从接收参数、读取文件到模块化重构、TDD开发和错误处理，这篇教程将为你揭开
用 Rust 打造命令行利器：从零到一实现 mini-grep
在开发中，命令行工具以其高效和灵活深受开发者喜爱。本文通过一个 Rust 实现的 mini-grep 项目，带你从零开始学习如何构建一个功能强大的命令行程序。从接收参数、读取文件到模块化重构、TDD 开发和错误处理，这篇教程将为你揭开 Rust 在命令行开发中的魅力，助你快速上手！
本文详细介绍了使用 Rust 开发命令行工具 mini-grep 的完整过程，涵盖以下核心内容：
- 接收和解析命令行参数，实现基本的搜索功能；
- 读取文件内容并输出匹配结果；
- 通过模块化和错误处理优化代码结构；
- 引入 TDD（测试驱动开发）确保代码健壮性；
- 使用环境变量支持大小写敏感搜索；
- 将错误信息输出到标准错误，提升用户体验。
通过逐步重构和代码示例，你将掌握 Rust 的核心特性和命令行程序开发的实用技巧。
一、实例：接收命令行参数
本文内容
- 1 接收命令行参数
- 2 读取文件
- 3 重构：改进模块和错误处理
- 4 使用 TDD（测试驱动开发）开发库功能
- 5 使用环境变量
- 6 将错误消息写入标准错误而不是标准输出
创建项目
~/rust
➜ cargo new minigrep
Created binary (application) `minigrep` package
~/rust
➜ cd minigrep
minigrep on master [?] via 🦀 1.67.1
➜ c // code .
minigrep on master [?] via 🦀 1.67.1
➜
main.rs 文件
use std::env;
fn main() {
let args: Vec<String> = env::args().collect();
// env::args_os() // OsString
// println!("{:?}", args);
let query = &args[1];
let filename = &args[2];
println!("Search for {}", query);
println!("In file {}", filename);
}
运行
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run
Compiling minigrep v0.1.0 (/Users/qiaopengjun/rust/minigrep)
Finished dev [unoptimized + debuginfo] target(s) in 0.17s
Running `target/debug/minigrep`
["target/debug/minigrep"]
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run 1234 abcd
Finished dev [unoptimized + debuginfo] target(s) in 0.02s
Running `target/debug/minigrep 1234 abcd`
["target/debug/minigrep", "1234", "abcd"]
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1 took 2.3s
➜
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1 took 2.3s
➜ cargo run abcd readme.txt
Compiling minigrep v0.1.0 (/Users/qiaopengjun/rust/minigrep)
Finished dev [unoptimized + debuginfo] target(s) in 0.39s
Running `target/debug/minigrep abcd readme.txt`
Search for abcd
In file readme.txt
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1 took 2.4s
➜ 二、实例：读取文件
src/main.rs 文件
use std::env;
use std::fs;
fn main() {
let args: Vec<String> = env::args().collect();
// env::args_os() // OsString
// println!("{:?}", args);
let query = &args[1];
let filename = &args[2];
println!("Search for {}", query);
println!("In file {}", filename);
let contents = fs::read_to_string(filename)
.expect("Something went wrong reading the file");
println!("With text:\n{}", contents);
}
poem.txt 文件
I'm nobody! Who are you?
Are you nobody, too?
Then there's a pair of us - don't tell!
They'd banish us, you know.
How dreary to be somebody!
How public, like a frog
To tell your name the livelong day
To an admiring bog!
运行
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run the poem.txt
Compiling minigrep v0.1.0 (/Users/qiaopengjun/rust/minigrep)
Finished dev [unoptimized + debuginfo] target(s) in 0.41s
Running `target/debug/minigrep the poem.txt`
Search for the
In file poem.txt
With text:
I'm nobody! Who are you?
Are you nobody, too?
Then there's a pair of us - don't tell!
They'd banish us, you know.
How dreary to be somebody!
How public, like a frog
To tell your name the livelong day
To an admiring bog!
minigrep on master [?] is 📦 0.1.0 via 🦀 三、实例：重构（上：改善模块化）
二进制程序关注点分离的指导性原则
- 将程序拆分为 main.rs 和 lib.rs ，将业务逻辑放入 lib.rs
- 当命令行解析逻辑较少时，将它放在 main.rs 也行
- 当命令行解析逻辑变复杂时，需要将它从 main.rs 提取到 lib.rs
经过上述拆分，留在 main 的功能有
- 使用参数值调用命令行解析逻辑
- 进行其它配置
- 调用 lib.rs 中的 run 函数
- 处理 run 函数可能出现的错误
优化一：
use std::env;
use std::fs;
fn main() {
let args: Vec<String> = env::args().collect();
let (_query, filename) = parse_config(&args);
let contents = fs::read_to_string(filename).expect("Something went wrong reading the file");
println!("With text:\n{}", contents);
}
fn parse_config(args: &[String]) -> (&str, &str) {
let query = &args[1];
let filename = &args[2];
(query, filename)
}
优化二：
use std::env;
use std::fs;
fn main() {
let args: Vec<String> = env::args().collect();
let config = parse_config(&args);
let contents = fs::read_to_string(config.filename).expect("Something went wrong reading the file");
println!("With text:\n{}", contents);
println!("query: {:?}", config.query)
}
struct Config {
query: String,
filename: String,
}
fn parse_config(args: &[String]) -> Config {
let query = args[1].clone();
let filename = args[2].clone();
Config { query, filename }
}
优化三：
use std::env;
use std::fs;
fn main() {
let args: Vec<String> = env::args().collect();
let config = Config::new(&args);
let contents =
fs::read_to_string(config.filename).expect("Something went wrong reading the file");
println!("With text:\n{}", contents);
println!("query: {:?}", config.query)
}
struct Config {
query: String,
filename: String,
}
impl Config {
fn new(args: &[String]) -> Config {
let query = args[1].clone();
let filename = args[2].clone();
Config { query, filename }
}
}
四、实例：重构（中：错误处理）
错误信息：
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run
Compiling minigrep v0.1.0 (/Users/qiaopengjun/rust/minigrep)
Finished dev [unoptimized + debuginfo] target(s) in 0.11s
Running `target/debug/minigrep`
thread 'main' panicked at 'index out of bounds: the len is 1 but the index is 1', src/main.rs:20:21
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ 优化一：
use std::env;
use std::fs;
fn main() {
let args: Vec<String> = env::args().collect();
let config = Config::new(&args);
let contents =
fs::read_to_string(config.filename).expect("Something went wrong reading the file");
println!("With text:\n{}", contents);
println!("query: {:?}", config.query)
}
struct Config {
query: String,
filename: String,
}
impl Config {
fn new(args: &[String]) -> Config {
if args.len() < 3 {
panic!("not enough arguments");
}
let query = args[1].clone();
let filename = args[2].clone();
Config { query, filename }
}
}
优化二：
use std::env;
use std::fs;
use std::process;
fn main() {
let args: Vec<String> = env::args().collect();
let config = Config::new(&args).unwrap_or_else(|err| {
println!("Problem parsing arguments: {}", err);
process::exit(1);
});
let contents =
fs::read_to_string(config.filename).expect("Something went wrong reading the file");
println!("With text:\n{}", contents);
println!("query: {:?}", config.query)
}
struct Config {
query: String,
filename: String,
}
impl Config {
fn new(args: &[String]) -> Result<Config, &'static str> {
if args.len() < 3 {
return Err("not enough arguments");
}
let query = args[1].clone();
let filename = args[2].clone();
Ok(Config { query, filename })
}
}
五、实例：重构（下：将业务逻辑移至 lib.rs）
优化一：
use std::env;
use std::fs;
use std::process;
use std::error::Error;
fn main() {
let args: Vec<String> = env::args().collect();
let config = Config::new(&args).unwrap_or_else(|err| {
println!("Problem parsing arguments: {}", err);
process::exit(1);
});
if let Err(e) = run(config) {
println!("Application error: {}", e);
process::exit(1);
}
}
fn run(config: Config) -> Result<(), Box<dyn Error>> {
let contents =
fs::read_to_string(config.filename)?;
println!("With text:\n{}", contents);
println!("query: {:?}", config.query);
Ok(())
}
struct Config {
query: String,
filename: String,
}
impl Config {
fn new(args: &[String]) -> Result<Config, &'static str> {
if args.len() < 3 {
return Err("not enough arguments");
}
let query = args[1].clone();
let filename = args[2].clone();
Ok(Config { query, filename })
}
}
迁移 模块化：
src/mian.rs 文件
use minigrep::Config;
use std::env;
use std::process;
fn main() {
let args: Vec<String> = env::args().collect();
let config = Config::new(&args).unwrap_or_else(|err| {
println!("Problem parsing arguments: {}", err);
process::exit(1);
});
if let Err(e) = minigrep::run(config) {
println!("Application error: {}", e);
process::exit(1);
}
}
src/lib.rs 文件
use std::error::Error;
use std::fs;
pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
let contents = fs::read_to_string(config.filename)?;
println!("With text:\n{}", contents);
println!("query: {:?}", config.query);
Ok(())
}
pub struct Config {
pub query: String,
pub filename: String,
}
impl Config {
pub fn new(args: &[String]) -> Result<Config, &'static str> {
if args.len() < 3 {
return Err("not enough arguments");
}
let query = args[1].clone();
let filename = args[2].clone();
Ok(Config { query, filename })
}
}
六、使用 TDD（测试驱动开发）编写库功能
测试驱动开发 TDD（Test-Driven Development）
- 编写一个会失败的测试，运行该测试，确保它是按照预期的原因失败
- 编写或修改刚好足够的代码，让新测试通过
- 重构刚刚添加或修改的代码，确保测试会始终通过
- 返回步骤 1 ，继续
src/lib.rs 文件
use std::error::Error;
use std::fs;
pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
let contents = fs::read_to_string(config.filename)?;
for line in search(&config.query, &contents) {
println!("line: {}", line);
}
// println!("With text:\n{}", contents);
// println!("query: {:?}", config.query);
Ok(())
}
pub struct Config {
pub query: String,
pub filename: String,
}
impl Config {
pub fn new(args: &[String]) -> Result<Config, &'static str> {
if args.len() < 3 {
return Err("not enough arguments");
}
let query = args[1].clone();
let filename = args[2].clone();
Ok(Config { query, filename })
}
}
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
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn one_result() {
let query = "duct";
let contents = "\
Rust:
safe, fast, productive.
Pick three.";
assert_eq!(vec!["safe, fast, productive."], search(query, contents))
}
}
运行
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run frog poem.txt
Compiling minigrep v0.1.0 (/Users/qiaopengjun/rust/minigrep)
Finished dev [unoptimized + debuginfo] target(s) in 0.18s
Running `target/debug/minigrep frog poem.txt`
line: How public, like a frog
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run body poem.txt
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running `target/debug/minigrep body poem.txt`
line: I'm nobody! Who are you?
line: Are you nobody, too?
line: How dreary to be somebody!
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run 123 poem.txt
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running `target/debug/minigrep 123 poem.txt`
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ 七、实例：使用环境变量
src/lib.rs 文件
use std::error::Error;
use std::fs;
use std::env;
pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
let contents = fs::read_to_string(config.filename)?;
let results = if config.case_sensitive {
search(&config.query, &contents)
} else {
search_case_insensitive(&config.query, &contents)
};
for line in results {
println!("line: {}", line);
}
// println!("With text:\n{}", contents);
// println!("query: {:?}", config.query);
Ok(())
}
pub struct Config {
pub query: String,
pub filename: String,
pub case_sensitive: bool,
}
impl Config {
pub fn new(args: &[String]) -> Result<Config, &'static str> {
if args.len() < 3 {
return Err("not enough arguments");
}
let query = args[1].clone();
let filename = args[2].clone();
let case_sensitive = env::var("CASE_INSENSITIVE").is_err();
Ok(Config { query, filename, case_sensitive })
}
}
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
}
pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
let mut results = Vec::new();
let query = query.to_lowercase();
for line in contents.lines() {
if line.to_lowercase().contains(&query) {
results.push(line);
}
}
results
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
// fn one_result() {
// let query = "duct";
// let contents = "\
// Rust:
// safe, fast, productive.
// Pick three.";
// assert_eq!(vec!["safe, fast, productive."], search(query, contents))
// }
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, fase, productive.
Pick three.
Trust me.";
assert_eq!(vec!["Rust:", "Trust me."], search_case_insensitive(query, contents))
}
}
运行
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run to poem.txt
Compiling minigrep v0.1.0 (/Users/qiaopengjun/rust/minigrep)
Finished dev [unoptimized + debuginfo] target(s) in 0.40s
Running `target/debug/minigrep to poem.txt`
line: Are you nobody, too?
line: How dreary to be somebody!
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ CASE_INSENSITIVE=1 cargo run to poem.txt
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running `target/debug/minigrep to poem.txt`
line: Are you nobody, too?
line: How dreary to be somebody!
line: To tell your name the livelong day
line: To an admiring bog!
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜
八、实例：将错误信息输出到标准错误
标准输出 VS 标准错误
- 标准输出：stdout
- println!
- 标准错误：stderr
- eprintln!
src/main.rs 文件
use minigrep::Config;
use std::env;
use std::process;
fn main() {
let args: Vec<String> = env::args().collect();
let config = Config::new(&args).unwrap_or_else(|err| {
eprintln!("Problem parsing arguments: {}", err);
process::exit(1);
});
if let Err(e) = minigrep::run(config) {
eprintln!("Application error: {}", e);
process::exit(1);
}
}
运行
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run > output.txt
Compiling minigrep v0.1.0 (/Users/qiaopengjun/rust/minigrep)
Finished dev [unoptimized + debuginfo] target(s) in 0.14s
Running `target/debug/minigrep`
Problem parsing arguments: not enough arguments
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ cargo run to poem.txt > output.txt
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running `target/debug/minigrep to poem.txt`
minigrep on master [?] is 📦 0.1.0 via 🦀 1.67.1
➜ 总结
通过 mini-grep 项目，我们不仅实现了一个功能完备的命令行工具，还深入探索了 Rust 的模块化、错误处理和测试驱动开发等特性。从简单的参数解析到复杂的功能实现，Rust 的安全性和性能优势得到了充分体现。无论你是 Rust 新手还是有一定经验的开发者，这个项目都能帮助你加深对 Rust 的理解，并为开发更复杂的命令行工具打下坚实基础。快动手试试，打造属于你的命令行利器吧！
参考
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