Turning Blog HTML into RSS, the Low-Level Way (in C++)

Turning Blog HTML into RSS, the Low-Level Way (in C++)

If you publish long-form posts on the web, you’ve probably felt the friction of keeping your RSS feed in sync. I did too. So I wrote a tiny command-line tool in C++ that converts a finished blog post page (the raw HTML file itself, not just the body) into a ready-to-drop <item> block for your RSS feed. Because yes—CLI is fun, and C++ is low-level, baby. 🛠️

TL;DR

  • What it does: Reads a full raw blog HTML page (not just the body) → emits a valid RSS <item> XML snippet.
  • Why it’s useful: No separate markdown front matter or duplication. Your source of truth is the rendered page.
  • How to use: ./a.out post.html rss.xml "My Title" "https://example.com/post" "2025-10-04"
  • Where it lives: github.com/julienlargetpiet/automate_rss

The Problem

An RSS feed wants clean metadata and safe HTML inside <description> and/or <content:encoded>. Most blogs already produce a canonical HTML page. Duplicating metadata (title, dates, canonical URL, description, tags) across templates, markdown front-matter, and an RSS generator is fragile and error-prone.

Goal: parse the final HTML, extract only what we need, sanitize it, and output a single <item> you can paste into your feed file—or pipe into your generator.

What the Tool Extracts

  • Title (you pass it as an argument)
  • Link (you pass it as an argument)
  • Date (from argument or generated at runtime)
  • Content (your entire HTML page, not just the body, properly escaped for XML safety — for example < → &lt;, > → &gt;, and if there’s any raw &, it must be converted into &amp;)

Important: Ampersands in HTML

If your source HTML contains raw & (e.g., “A & B”), it must be escaped to &amp; before it’s placed inside XML. Otherwise your RSS will break.

Before: A & B

After (in RSS/XML): A &amp; B

Why C++?

I like low-level control. With C++ you handle strings, escaping, and file IO directly. Writing a simple CLI tool in C++ is lightweight and dependency-free, and frankly, fun.

Example Usage

$ g++ -O3 automate_rss.cpp
$ ./a.out html_data.html rss_data.xml "My Blog Post" "https://example.com/post" "2025-10-04"

Your rss_data.xml should contain a ? placeholder where you want the new <item> inserted.

Minimal Example of the Inserted Item

<item>
  <title>My Blog Post</title>
  <link>https://example.com/post</link>
  <pubDate>Sat, 04 Oct 2025 12:00:00 GMT</pubDate>
  <description>&lt;html&gt;...full page content escaped...&lt;/html&gt;</description>
</item>

What’s Next

  • Smarter HTML extraction (custom selectors).
  • Optional support for <content:encoded> for full-content feeds.
  • Date auto-detection from meta tags.
  • Configurable insertion strategies beyond a single placeholder.

Check it out on GitHub: julienlargetpiet/automate_rss