src/doc/book/listings/ch12-an-io-project/no-listing-01-handling-errors-in-main/src/main.rs

   1 use std::env;
   2 use std::error::Error;
   3 use std::fs;
   4 use std::process;
   5
   6 // ANCHOR: here
   7 fn main() {
   8     // --snip--
   9
  10     // ANCHOR_END: here
  11     let args: Vec<String> = env::args().collect();
  12
  13     let config = Config::new(&args).unwrap_or_else(|err| {
  14         println!("Problem parsing arguments: {}", err);
  15         process::exit(1);
  16     });
  17
  18     // ANCHOR: here
  19     println!("Searching for {}", config.query);
  20     println!("In file {}", config.filename);
  21
  22     if let Err(e) = run(config) {
  23         println!("Application error: {}", e);
  24
  25         process::exit(1);
  26     }
  27 }
  28 // ANCHOR_END: here
  29
  30 fn run(config: Config) -> Result<(), Box<dyn Error>> {
  31     let contents = fs::read_to_string(config.filename)?;
  32
  33     println!("With text:\n{}", contents);
  34
  35     Ok(())
  36 }
  37
  38 struct Config {
  39     query: String,
  40     filename: String,
  41 }
  42
  43 impl Config {
  44     fn new(args: &[String]) -> Result<Config, &str> {
  45         if args.len() < 3 {
  46             return Err("not enough arguments");
  47         }
  48
  49         let query = args[1].clone();
  50         let filename = args[2].clone();
  51
  52         Ok(Config { query, filename })
  53     }
  54 }