---
title: "Discussion on \"How to Build an Online Judge, Part 1: Understanding stdin, stdout, stderr, and Exit Codes\" | Hashnode"
description: "Discussion on \"How to Build an Online Judge, Part 1: Understanding stdin, stdout, stderr, and Exit Codes\". Understanding how programs receive data, produce results, and report success or failure—the first step toward judging code."
url: "https://hashnode.com/posts/stdin-stdout-stderr-and-exit-codes/6aa2df732644e5a77473e445"
---

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# [How to Build an Online Judge, Part 1: Understanding stdin, stdout, stderr, and Exit Codes](https://systemsfromscratch.hashnode.dev/stdin-stdout-stderr-and-exit-codes?utm_source=hashnode&utm_medium=feed)

Understanding how programs receive data, produce results, and report success or failure—the first step toward judging code.

Sep 10 · 7 min read · systemsfromscratch.hashnode.dev  
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## Written by

[Siddharth Lalwani](https://hashnode.com/@siddharthlalwani)

@siddharthlalwani

  
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I like codex and codex likes me back.

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