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Rust program to append data into an existing file

Rust | File I/O Example: Write a program to append data into an existing file.
Last Updated : October 30, 2021

Problem Statement

In this program, we will open an existing file in append mode and write text data into the file using the write_all() method, and print the appropriate message.

Program/Source Code

The source code to append data into the existing file is given below. The given program is compiled and executed on UBUNTU 18.04 successfully.

// Rust program to append data into existing file

use std::fs::OpenOptions;
use std::io::Write;

fn main() {
    let mut fileRef = OpenOptions::new().append(true).open("sample.txt").expect("Unable to open file");   
    
    fileRef.write_all("www.includehelp.com\n".as_bytes()).expect("write failed");
    println!("Data appended successfully");
}

Output

$ rustc main.rs

$ ./main
Data appended successfully

$ cat sample.txt 
Hello World
Hello India
www.includehelp.com

Explanation

In the main() function, we opened an existing file "sample.txt" in append mode. Then we wrote text data into the file using the write_all() method and printed file data.

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