Rust Function: Read file contents

Last update on December 21 2024 10:19:49 (UTC/GMT +8 hours)

Write a Rust function that reads a file and returns Result<String, std::io::Error>, where the string contains the file's contents.

Sample Solution:

Rust Code:

// Import the fs module from the standard library, which provides file system operations.
use std::fs;
// Import the io module from the standard library, which provides input/output functionality.
use std::io;

// Define a function named 'read_file_contents' that takes a file path as input and returns a Result<String, io::Error>.
fn read_file_contents(file_path: &str) -> Result<String, io::Error> {
    // Use 'fs::read_to_string' to read the contents of the file specified by 'file_path' into a String.
    match fs::read_to_string(file_path) {
        // If reading the file is successful, return the contents wrapped in Ok.
        Ok(contents) => Ok(contents),
        // If an error occurs while reading the file, return the error wrapped in Err.
        Err(error) => Err(error),
    }
}

// Define the main function, where the program execution starts.
fn main() {
    // Specify the file path of the file to be read.
    let file_path = "example.txt"; // Adjust the file path as needed
    // Call the `read_file_contents` function with the specified file path and handle the returned Result.
    match read_file_contents(file_path) {
        // If reading the file is successful, print its contents.
        Ok(contents) => println!("File contents: {}", contents),
        // If an error occurs while reading the file, print the error message.
        Err(error) => eprintln!("Error reading file: {}", error),
    }
}

Output:

Error reading file: No such file or directory (os error 2)

Explanation:

Here's a brief explanation of the above Rust code:

• Imports:
• use std::fs;: This imports the file system module from the standard library, allowing access to file-related functions.
• use std::io;: This imports the input/output module from the standard library, which provides types and functions for handling input and output operations.
• Function read_file_contents:
• This function takes a file path (&str) as input and returns a Result<String, io::Error>.
• It uses fs::read_to_string to read the contents of the file specified by the 'file_path' parameter.
• The 'match' statement handles the result of fs::read_to_string:
• If reading the file is successful (Ok(contents)), it returns the contents wrapped in 'Ok'.
• If an error occurs (Err(error)), it returns the error wrapped in 'Err'.
• Main function (main()):
• This is where the program execution starts.
• It specifies the file path of the file to be read ('example.txt' in this case).
• It calls the "read_file_contents()" function with the specified file path and handles the returned 'Result'.
• If reading the file is successful (Ok(contents)), it prints the file contents.
• If an error occurs while reading the file (Err(error)), it prints the error message.

Rust Code Editor:

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