标准输出 vs 标准错误

  • 标准输出：stdout
    • println!
  • 标准错误：stderr
    • eprintln!

      标准输出重定向：cargo run > output.txt 

  1. use minigrep::Config;
  2. use std::env;
  3. use std::process;
  5. fn main() {
  6.     let args: Vec<String> = env::args().collect();
  8.     let config = Config::new(&args).unwrap_or_else(|err| {
  9.         eprintln!("Problem parsing arguments: {}", err);
  10.         process::exit(1);
  11.     });
  13.     if let Err(e) = minigrep::run(config) {
  14.         eprintln!("Application error: {}", e);
  15.         process::exit(1);
  16.     }
  17. }
  1. use std::env;
  2. use std::error::Error;
  3. use std::fs;
  5. pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
  6.   let contents = fs::read_to_string(config.filename)?;
  7.   let results = if config.case_sensitive {
  8.     search(&config.query, &contents)
  9.   } else {
  10.     search_case_insensitive(&config.query, &contents)
  11.   };
  12.   for line in results {
  13.     println!("{}", line);
  14.   }
  15.   Ok(())
  16. }
  18. pub struct Config {
  19.   pub query: String,
  20.   pub filename: String,
  21.   pub case_sensitive: bool,
  22. }
  24. impl Config {
  25.   pub fn new(args: &[String]) -> Result<Config, &'static str> {
  26.     if args.len() < 3 {
  27.       return Err("not enough arguments");
  28.     }
  29.     let query = args[1].clone();
  30.     let filename = args[2].clone();
  31.     let case_sensitive = env::var("CASE_INSENSITIVE").is_err();
  32.     Ok(Config {
  33.       query,
  34.       filename,
  35.       case_sensitive,
  36.     })
  37.   }
  38. }
  40. pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
  41.   let mut results = Vec::new();
  42.   for line in contents.lines() {
  43.     if line.contains(query) {
  44.       results.push(line);
  45.     }
  46.   }
  47.   results
  48. }
  50. pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
  51.   let mut results = Vec::new();
  52.   let query = query.to_lowercase();
  53.   for line in contents.lines() {
  54.     if line.to_lowercase().contains(&query) {
  55.       results.push(line);
  56.     }
  57.   }
  58.   results
  59. }
  61. #[cfg(test)]
  62. mod tests {
  63.   use super::*;
  65.   #[test]
  66.   fn case_sensitive() {
  67.     let query = "duct";
  68.     let contents = "\
  69. Rust:
  70. safe, fast, productive.
  71. Pick three.
  72. Duct tape.";
  74.     assert_eq!(vec!["safe, fast, productive."], search(query, contents));
  75.   }
  77.   #[test]
  78.   fn case_insensitive() {
  79.     let query = "rUst";
  80.     let contents = "\
  81. Rust:
  82. safe, fast, productive.
  83. Pick three.
  84. Trust me.";
  86.     assert_eq!(
  87.       vec!["Rust:", "Trust me."],
  88.       search_case_insensitive(query, contents)
  89.     );
  90.   }
  91. }