项目实例：- 命令行程序一、实例：接收命令行参数
本章内容
- 12.1 接收命令行参数
- 12.2 读取文件
- 12.3 重构：改进模块和错误处理
- 12.4 使用 TDD（测试驱动开发）开发库功能
- 12.5 使用环境变量
- 12.6 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 minigrepminigrep 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 = 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 abcdIn file readme.txtminigrep 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 = 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 frogTo tell your name the livelong dayTo 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 theIn file poem.txtWith 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 frogTo tell your name the livelong dayTo 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 = 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 = 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 = 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:20:21note: run with `RUST_BACKTRACE=1` environment variable to display a backtraceminigrep on master [?] is ? 0.1.0 via ? 1.67.1 ➜ 优化一：
use std::env;use std::fs;fn main() { let args: Vec = 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 = 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 { 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 = 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> { 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 { 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 = 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> { 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 { 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> { 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 { 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(query: &str, contents: &'a str) -> Vec { 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 frogminigrep 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> { 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 { 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(query: &str, contents: &'a str) -> Vec { let mut results = Vec::new(); for line in contents.lines() { if line.contains(query) { results.push(line); } } results}pub fn search_case_insensitive(query: &str, contents: &'a str) -> Vec { 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 dayline: 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 = 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 argumentsminigrep 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 ➜ 本文来自博客园，作者：QIAOPENGJUN，转载请注明原文链接：https://www.cnblogs.com/QiaoPengjun/p/17290999.html