Rust 檔案操作 read_to_string和read - 讀取檔案

Rust 檔案操作 read_to_string和read - 讀取檔案

  12月 12, 2023    LaGee

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最近有一個想要做的小東西

會先用到操作文檔

這篇文章先稍微介紹一下兩個讀取的方法

分別是read_to_string、read

而讀取文件總要有個文件讓我讀

因此在目錄底下創建一個poem.txt

poem.txt的文件裡面內容為一首詩

I'm nobody! Who are you?

Are you nobody, too?

Then there's a pair of us - don't tell!

They'd banish us, you know.

How dreary to be somebody!

How public, like a frog

To tell your name the livelong day

To an admiring bog!

std::fs[1]

文件操作的放在std::fs底下

fs為filesystem

這個包常用於操作系統文件

常見的包括create、read、write等等

當想操作文件時都必須

use std::fs;

read_to_string[2]

read_to_string為將文件內容放入字串中

文件這樣解釋

pub fn read_to_string<P: AsRef<Path>>(path: P) -> Result<String>

輸入一個路徑，最後輸出一個Result

看一個範例打法

use std::fs;

fn main() {

    let file_path = "poem.txt";

    let contents = fs::read_to_string(file_path)

        .expect("Should have been able to read the file");

    println!("{}", contents);

}

I'm nobody! Who are you? Are you nobody, too? Then there's a pair of us - don't tell! They'd banish us, you know. How dreary to be somebody! How public, like a frog To tell your name the livelong day To an admiring bog!

先透過file_path指定我的路徑

路徑也可以使用絕對路徑

這邊先使用相對路徑

contents為檔案的內容，並且將檔案內容轉為string

如果讀不到檔案則會直接panic，並顯示

thread 'main' panicked at 'Should have been able to read the file: Os

{ code: 2, kind: NotFound, message: "系統找不到指定的檔案。" }', src\main.rs:6:10

stack backtrace:

read[3]

read為將檔案內容轉vector

文件這樣解釋

pub fn read<P: AsRef<Path>>(path: P) -> Result<Vec<u8>>

輸入一個路徑，輸出為result

並且如果成功內容為Vec<u8>

u8意思為會把每個ASCII碼輸出

看個例子

use std::fs;

fn main() {

    let file_path = "D:\\Blog\\rust\\poem.txt";

    let contents = fs::read(file_path)

        .expect("Should have been able to read the file");

    println!("{:?}", contents);

}

[73, 39, 109, 32, 110, 111, 98, 111, 100, 121, 33, 32, 87, 104, 111, 32, 97, 114, 101,

32, 121, 111, 117, 63, 13, 10, 65, 114, 101, 32, 121, 111, 117, 32, 110, 111, 98, 111,

100, 121, 44, 32, 116, 111, 111, 63, 13, 10, 84, 104, 101, 110, 32, 116, 104, 101,

114, 101, 39, 115, 32, 97, 32, 112, 97, 105, 114, 32, 111, 102, 32, 117, 115, 32, 45,

32, 100, 111, 110, 39, 116, 32, 116, 101, 108, 108, 33, 13, 10, 84, 104, 101, 121,

39, 100, 32, 98, 97, 110, 105, 115, 104, 32, 117, 115, 44, 32, 121, 111, 117, 32, 107,

110, 111, 119, 46, 13, 10, 13, 10, 72, 111, 119, 32, 100, 114, 101, 97, 114, 121, 32,

116, 111, 32, 98, 101, 32, 115, 111, 109, 101, 98, 111, 100, 121, 33, 13, 10, 72,

111, 119, 32, 112, 117, 98, 108, 105, 99, 44, 32, 108, 105, 107, 101, 32, 97, 32, 102,

114, 111, 103, 13, 10, 84, 111, 32, 116, 101, 108, 108, 32, 121, 111, 117, 114, 32, 110, 97, 109, 101, 32, 116, 104, 101, 32, 108, 105, 118, 101, 108, 111, 110, 103, 32,

100, 97, 121, 13, 10, 84, 111, 32, 97, 110, 32, 97, 100, 109, 105, 114, 105, 110, 103,

32, 98, 111, 103, 33, 13, 10]

這次使用絕對路徑

使用絕對路徑要兩個\\才表示一個\

如果只使用一個\會跟後面英文組合

例如\n就組合成換行

關於更多斜線的用途可以看看這篇文章[4]

而輸出可以看到是vector

裡面都是數字，每個數字表示一個字

拿個維基百科的ASCII[5]來對照一下

可以翻譯成詩中內容

參考資料

[1] https://doc.rust-lang.org/std/fs/

[2] https://doc.rust-lang.org/std/fs/fn.read_to_string.html

[3] https://doc.rust-lang.org/std/fs/fn.read.html

[4] https://tw.crystal-lang.org/docs/syntax_and_semantics/literals/string.html

[5] https://zh.wikipedia.org/zh-tw/ASCII