How to Write Files in Rust

Oliver Jumpertz
5 min readMar 23
How to Write Files in Rust

All software has to write data to the file system at some point. This is also true for programs written in Rust. Log messages need to be persisted (as long as they are not just written to stdout), and data needs to be saved for later, or else. Naturally, writing data is the opposite of reading data.

There are multiple ways to deal with writing data to files in Rust. Some of these ways are easier than others, but all have their justification. Sometimes you directly want to write text into a file, and other times you write some kind of binary format. No matter your use case, Rust probably has a way to deal with it.

In this article, you will learn about common ways of how to write files in Rust.

Just in case you enjoy YouTube videos more than an article, you can also watch the video above instead!

Writing All Data to a File at Once

Regularly, you only want to persist data that you already have in memory. In this case, this method is one of the most straightforward ways to deal with it.

It allows you to write all data at once, and it doesn’t matter whether your data is a String or already in binary format. Additionally, a file is conveniently created for you if it does not exist yet.

Its advantages include:

  1. It is convenient to use
  2. It is merely one line of code
  3. fs::write takes care of everything for you

As usual, this method also has a few drawbacks, which are:

  1. It always overwrites the file
  2. Its performance highly depends on the size of your data — the more data you write, the longer it takes

If this is what you are looking for, then take a look at the following code as an example of how to write all data to a file at once:

Oliver Jumpertz

Software Engineer - Content Creator