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. }

    运行结果

    1. $ cargo run to poem.txt
    2. Are you nobody, too?
    3. How dreary to be somebody!
    5. $ CASE_INSENSITIVE=1 cargo run to poem.txt
    6. Are you nobody, too?
    7. How dreary to be somebody!
    8. To tell your name the livelong day
    9. To an admiring bog!