use serde::{Serialize, Deserialize};
use std::fs::File;
use std::io::prelude::*;
fn main() -> std::io::Result<()>{
let mut file = File::open("foo.txt")?;
let mut contents = String::new();
file.read_to_string(&mut contents)?;
println!("{}", contents);
assert_eq!(contents, "hello, world!");
Ok(())
}
$ cargo run
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.49s
Running `target/debug/sample`
bytes bytes bytes 8bytes
asdfghjkl
1234567890
thread ‘main’ panicked at src/main.rs:11:5:
assertion `left == right` failed
left: “bytes bytes bytes 8bytes\nasdfghjkl\n1234567890”
right: “hello, world!”
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
これも同じ
fn main() -> std::io::Result<()>{
let file = File::open("foo.txt")?;
let mut buf_reader = BufReader::new(file);
let mut contents = String::new();
buf_reader.read_to_string(&mut contents)?;
println!("{}", contents);
assert_eq!(contents, "hello, world!");
Ok(())
}
### 1行ずつ読み取る
use std::fs::File;
use std::io::{BufReader, BufRead, Error};
fn main() -> Result<(), Error>{
let path = "foo.txt";
let input = File::open(path)?;
let buffered = BufReader::new(input);
for line in buffered.lines() {
println!("{}", line?);
}
Ok(())
}
### ファイルの書き込み
fn main() -> std::io::Result<()>{
let mut buffer = File::create("hoge.txt")?;
buffer.write_all(b"some bytes\n hogehoge")?;
Ok(())
}
### 最終行に書き込み
use std::fs::OpenOptions;
use std::io::Write;
fn main() -> std::io::Result<()>{
let mut fileRef = OpenOptions::new()
.append(true)
.open("hoge.txt")
.expect("Unable to open file");
fileRef.write_all(b"last line\n").expect("write failed");
Ok(())
}
改行コードを入れないと、同じ列になってしまう。
さて、Structでやりたい。
