bun-file-io

Bun File I/O

Bun provides fast, optimized file operations via Bun.file() and Bun.write().

Reading Files

Bun.file()

// Create file reference (lazy, doesn't read yet)
const file = Bun.file("./data.txt");

// File properties
console.log(file.size);        // Size in bytes
console.log(file.type);        // MIME type
console.log(file.name);        // File path
console.log(await file.exists()); // Boolean

// Read content
const text = await file.text();
const json = await file.json();
const buffer = await file.arrayBuffer();
const bytes = await file.bytes();   // Uint8Array
const stream = file.stream();       // ReadableStream

Read Specific Types

// JSON file
const config = await Bun.file("config.json").json();

// Text file
const content = await Bun.file("readme.md").text();

// Binary file
const binary = await Bun.file("image.png").arrayBuffer();

// With import attributes
import data from "./data.json" with { type: "json" };
import text from "./content.txt" with { type: "text" };

Writing Files

Bun.write()

// Write string
await Bun.write("./output.txt", "Hello World");

// Write JSON
await Bun.write("./data.json", JSON.stringify({ key: "value" }, null, 2));

// Write binary
await Bun.write("./output.bin", new Uint8Array([1, 2, 3]));

// Write from Response
const response = await fetch("https://example.com/image.png");
await Bun.write("./image.png", response);

// Write from another file (efficient copy)
await Bun.write("./copy.txt", Bun.file("./original.txt"));

// Write with options
await Bun.write("./file.txt", "content", {
  mode: 0o644,  // Unix permissions
});

Appending

// Using Bun.file writer
const file = Bun.file("./log.txt");
const writer = file.writer();

writer.write("Line 1\n");
writer.write("Line 2\n");
await writer.flush();
writer.end();

// Or use node:fs
import { appendFile } from "node:fs/promises";
await appendFile("./log.txt", "New line\n");