RUST File handling - Read - Write

RUST allows reading and writing to files. The File struct represents a file. It allows a program to perform read-write operations on a file. All methods in the File struct return a variant of the io::Result enumeration.

RUST Reading a File

Reading a file requires two core pieces: File and Read.

Read a file to a String

use std::fs::File;
use std::io::Read;

fn main() {
    let mut data = String::new();
    let mut f = File::open("/etc/hosts").expect("Unable to open file");
    f.read_to_string(&mut data).expect("Unable to read string");
    println!("{}", data);
}

Read a file as a Vec

use std::fs::File;
use std::io::Read;

fn main() {
    let mut data = Vec::new();
    let mut f = File::open("/etc/hosts").expect("Unable to open file");
    f.read_to_end(&mut data).expect("Unable to read data");
    println!("{}", data.len());
}

RUST Writing a File

Writing a file is similar, except we use the Write trait and we always write out bytes. You can convert a String / &str to bytes with as_bytes:

use std::fs::File;
use std::io::Write;

fn main() {
    let data = "Some data!";
    let mut f = File::create("/tmp/foo").expect("Unable to create file");
    f.write_all(data.as_bytes()).expect("Unable to write data");
}

Conclusion

In this page (written and validated by A. Gawali) you learned about Rust File handling - Read - Write . What's Next? If you are interested in completing Rust tutorial, your next topic will be learning about: Rust Directory and folder handling - Create - Delete.

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