Bun: Process file line by line

In NodeJs I can use fs and readline to make an interface and read the file line by line this is usefull for large text files (for me 100GB +) how can I achieve similar thing using bun

I've tried to read the file like this:

const input = Bun.file("input.txt");

but it's the same as fs.readFile which is not what I want in this case.

Nodejs example

const readline = require("readline");
const fs = require("fs");


const input = fs.createReadStream("file.txt", {
  encoding: "utf16le",
});
const rl = readline.createInterface({ input });

rl.on("line", (line) => {
  // proccess line
})

Solution

As @GrafiCode mentioned in the comments

const foo = Bun.file("foo.txt");

does not read the file from the disk it creates BunFile which you can read in many ways one of them is stream

await foo.stream(); // contents as ReadableStream

you can read more here

An Example of how to read a file line by line

async function readFileLineByLine(filePath, onLineRead, onFinish) {
  const foo = Bun.file(filePath);

  const stream = await foo.stream();
  const decoder = new TextDecoder();

  let remainingData = "";

  for await (const chunk of stream) {
    const str = decoder.decode(chunk);

    remainingData += str; // Append the chunk to the remaining data

    // Split the remaining data by newline character
    let lines = remainingData.split(/\r?\n/);
    // Loop through each line, except the last one
    while (lines.length > 1) {
      // Remove the first line from the array and pass it to the callback
      onLineRead(lines.shift());
    }
    // Update the remaining data with the last incomplete line
    remainingData = lines[0];
  }

  return onFinish();
}

function onLineRead(line) {
  console.log("Line read: " + line);
}

function onFinish() {
  console.log("File read successfully");
}

readFileLineByLine("2.txt", onLineRead, onFinish);