Rust Function: Read file with Error handling

Last update on June 10 2025 07:13:16 (UTC/GMT +8 hours)

Write a Rust function that reads a file and prints its contents, handling file not found and permission errors.

Sample Solution:

Rust Code:

use std::fs; // Import the fs module for file handling

fn read_file(file_path: &str) {
    match fs::read_to_string(file_path) { // Attempt to read the file contents as a string
        Ok(contents) => { // If successful, print the file contents
            println!("File contents:");
            println!("{}", contents);
        }
        Err(error) => { // If an error occurs while reading the file
            match error.kind() { // Match on the type of error
                std::io::ErrorKind::NotFound => { // If file not found
                    println!("File not found: {}", file_path);
                }
                std::io::ErrorKind::PermissionDenied => { // If permission denied
                    println!("Permission denied to read file: {}", file_path);
                }
                _ => { // For other types of errors
                    println!("Error reading file {}: {}", file_path, error);
                }
            }
        }
    }
}

fn main() {
    let file_path1 = "test.txt"; // Specify the path of the text file
    let file_path2 = "example.txt"; // Specify the path of the text file
    let contents = "Rust Exercises!"; // Content to write to the file

    fs::write(file_path2, contents).expect("Failed to create file"); // Create the file with content

    read_file(file_path1); // Call the function to read and print the file contents
    read_file(file_path2); // Call the function to read and print the file contents
}

Output:

File not found: test.txt
File contents:
Rust Exercises!

Explanation:

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

The code imports the "fs" module from the standard library (std::fs) for file handling operations.
The "read_file()" function takes a file path (file_path: &str) as input and attempts to read the file's contents as a string using the "read_to_string()" function from the "fs" module.
Inside the "read_file()" function, it uses pattern matching ('match') to handle the 'Ok' and 'Err' cases:

If reading the file is successful ('Ok' variant), it prints the file contents.
If an error occurs while reading the file ('Err' variant), it further matches on the type of error:

If the error indicates that the file was not found ('NotFound' variant), it prints a corresponding message.
If the error indicates permission denied ('PermissionDenied' variant), it prints a corresponding message.
For any other type of error, it prints a generic error message.

In the main function:

It specifies two file paths ('file_path1' and 'file_path2') and the content to be written to 'file_path2'.
It uses the write function from the "fs" module to create the file specified by 'file_path2' with the specified content.
It then calls the "read_file()" function twice, passing 'file_path1' and 'file_path2' as arguments, respectively, to read and print the contents of the files.

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