Use Node.js Streams to Build CLI Tools That Handle Massive Files

Use Node.js Streams to Build CLI Tools That Handle Massive Files Most CLI tutorials show you how to read an entire file into memory, process it, and write the output. This works fine for small files. But when your tool needs to handle a 2 GB log file or process a continuous data feed, loading everything into memory will crash your process or make it unbearably slow. Node.js streams solve this problem elegantly. They let you process data piece by piece, keeping memory usage constant regardless of input size. In this article, we'll build a CLI tool that processes massive log files using streams — and learn patterns you can apply to any data-processing CLI. The Problem with readFile // This loads the ENTIRE file into memory import { readFile } from ' node:fs/promises ' ; const data = await readFile ( ' server.log ' , ' utf-8 ' ); const lines = data . split ( ' \n ' ); const errors = lines . filter ( line => line . includes ( ' ERROR ' )); For a 10 KB file? Fine. For a 2 GB production log?