Bun implements the node:fs module, which includes the fs.appendFile and fs.appendFileSync functions for appending content to files.
You can use fs.appendFile to asynchronously append data to a file, creating the file if it does not yet exist. The content can be a string or a Buffer.
import { appendFile } from "node:fs/promises";
await appendFile("message.txt", "data to append");
To use the non-Promise API:
import { appendFile } from "node:fs";
appendFile("message.txt", "data to append", err => {
if (err) throw err;
console.log('The "data to append" was appended to file!');
});
To specify the encoding of the content:
import { appendFile } from "node:fs";
appendFile("message.txt", "data to append", "utf8", callback);
To append the data synchronously, use fs.appendFileSync:
import { appendFileSync } from "node:fs";
appendFileSync("message.txt", "data to append", "utf8");
See the Node.js documentation for more information.