~/tutorials/009-reading-source.md

009: Reading a page's source

You have been reading rendered pages all along. This lesson is about the file underneath, and about the one line in that file that the page does not show you.

The same file, twice

open ~/tutorials/005-pipes.md
cat ~/tutorials/005-pipes.md | head -8

Two views of one file. open shows you the page the site renders. cat shows you the file itself, and the difference is the first eight lines.

---
title: 005: Pipes, or asking the tree a question
slug: tutorials/005
kind: lesson
tier: First Steps
order: 6
tags: [tutorials]
---

That block is frontmatter. The page reads it to decide what the card says and where the item sits. The shell prints it verbatim, because hiding it would make cat a lie.

One warning about open. It does not just show you a file, it moves you. After that first command you are standing in lesson 005, and the page you were reading is behind you. Two ways back, and neither needs you to remember anything:

cd ~/tutorials
open ~/tutorials/009

The line the page does not show you

Every news item carries a field called source, and it holds the address of the document the item was written from. Not a summary of it. Not a blog that mentioned it. The thing itself.

grep source ~/news/2026-09-21-litellm-mcp-auth-bypass.md

source: https://github.com/advisories/GHSA-7488-6r32-c95q

The card told you what happened. That line tells you who says so, and it is one command away on every item on this site. An article without its source is a signal with no antenna.

This is the whole reason the page renders from the file instead of a database. If the page and the file ever disagree, the file wins, and you do not need our word for it. cat is the check, and it works in a terminal you already have.

Try it

Pick any item on the news page and grep source its file. Get the address.
Open that address on your own machine. You are now reading the primary document.
Read the two side by side and decide whether our two sentences match it. If they do not, the file is on your side.

The third step is the point. You are not checking that we are honest here, you are checking whether the claim survives contact with the document it came from. Most of the sites you read will not hand you the means to do that at all.