Error Handling #4
https://doc.rust-lang.org/book/error-handling.html
use std::fs::File; use std::io::Read; use std::path::Path; fn file_double<P: AsRef<Path>>(file_path: P) -> i32 { let mut file = File::open(file_path).unwrap(); // error 1 let mut contents = String::new(); file.read_to_string(&mut contents).unwrap(); // error 2 let n: i32 = contents.trim().parse().unwrap(); // error 3 2 * n } fn main() { let doubled = file_double("foobar"); println!("{}", doubled); }
$ cargo run Compiling 5_7_error_handling v0.1.0 (file:///Users/miura/work/git-work/exercises/The_Rust_Programming_Language/5_7_error_handling) Finished debug [unoptimized + debuginfo] target(s) in 1.38 secs Running `target/debug/5_7_error_handling` thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Error { repr: Os { code: 2, message: "No such file or directory" } }', ../src/libcore/result.rs:837 note: Run with `RUST_BACKTRACE=1` for a backtrace. $ touch foobar $ cargo run Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs Running `target/debug/5_7_error_handling` thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ParseIntError { kind: Empty }', ../src/libcore/result.rs:837 note: Run with `RUST_BACKTRACE=1` for a backtrace. $ echo 1 > foobar (anaconda3-4.2.0) miura (master *) 5_7_error_handling $ cargo run Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs Running `target/debug/5_7_error_handling` 2