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How to append to a file in Rust?

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");
}

Above example only writes and does not append, so to append to the file we will need to use method: .append(true)

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

fn main() {
   let mut file = fs::OpenOptions::new()
      .write(true)
      .append(true) // This is needed to append to file
      .open("file.txt")
      .unwrap();
   file.write_all(b"to append");
   // or
   write!(file, "to append");
}

Conclusion

In this page (written and validated by ) you learned about How to append to a file in Rust? . What's Next? If you are interested in completing Rust tutorial, we encourage you simply to start here: Rust Tutorial.



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