Is it possible to replace content in a file without deleting the file?

Question

I am wondering is it possible to replace contents without? I have tried this with file.write(), however, it has just been added to the content of the file, not replacing it. Does it possible to replace the contents in a file without deleting the file itself?

the_json_file.write_all(inside_da_file.as_bytes()).expect("Failed to write");I wanted to clear out the file before I write into it.

Hi @TaceCat, please give us an example (code) of what you want to do — Gedeon Mutshipayi, Feb 26 '22 at 11:06
Does [How to replace a word in a file in a .txt](https://stackoverflow.com/questions/27215396/how-to-replace-a-word-in-a-file-in-a-txt) help? — Andrew Morton, Feb 26 '22 at 11:06
Hi @gedflod, I have edited it and what I wanted to do is listed on top. — Taco Cat, Feb 26 '22 at 11:26
Duplicate: https://stackoverflow.com/questions/65782872/how-to-delete-the-contents-of-a-file-before-writing-to-it-in-rust — Herohtar, Feb 27 '22 at 09:11

score 4 · Accepted Answer · answered Feb 26 '22 at 11:44

As documented under OpenOptions::truncate:

Sets the option for truncating a previous file.

If a file is successfully opened with this option set it will truncate the file to 0 length if it already exists.

The file must be opened with write access for truncate to work.

Examples
use std::fs::OpenOptions;

let file = OpenOptions::new().write(true).truncate(true).open("foo.txt");

Alternatively, to truncate the file after it has been opened, there's File::set_len followed by Seek::rewind:

use std::io::{Seek, Write};

the_json_file.set_len(0).unwrap();
the_json_file.rewind().unwrap();
the_json_file.write_all(inside_da_file.as_bytes()).expect("Failed to write");

Is it possible to replace content in a file without deleting the file?

1 Answers1

Examples