split-urls.js

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

async function processUrls() {
  const inputFile = path.join(__dirname, "__urls.csv");

  const fileStream = fs.createReadStream(inputFile);
  const rl = readline.createInterface({
    input: fileStream,
    crlfDelay: Infinity,
  });

  for await (const line of rl) {
    if (!line.trim()) {
      continue;
    }

    const parts = line.split(",");
    const prefix = parts[0].substring(0, 3);
    const outputFile = path.join(__dirname, "split", `${prefix}.csv`);

    fs.appendFileSync(outputFile, line + "\n");
  }

  console.log("Done processing URLs");
}

processUrls().catch(console.error);