Extract frontmatter metadata

Goal: Pull a document’s YAML frontmatter out as structured data, e.g. to read title/tags for a static-site index.

Prerequisites: None.

Query

.yaml | frontmatter

$ mq '.yaml | frontmatter' post.md

Input

---
title: Hello
tags: [a, b]
---

# Body

Output

{"title": "Hello", "tags": ["a", "b"]}

Notes

• Grab a single field by chaining get("title"), e.g. .yaml | frontmatter | get("title"). A plain .title selector won’t work, since that’s a Markdown-node selector, not a dict-key accessor. Bracket access also works (frontmatter()["title"]), but only with the parentheses kept. frontmatter["title"] (no parens) tries to index the function itself and errors.
• Gotcha: -F json/-F csv don’t give a clean metadata index here. Since the result is coming from a Markdown document, mq wraps the dict in a synthetic node before serializing it (e.g. -F json gives {"type": "Text", "value": "{\"title\": ...}"} instead of the dict’s fields directly). Default output doesn’t have this problem: mq '.yaml | frontmatter' docs/**/*.md prints one JSON object per file, one per line, which you can pipe into jq -s to build an array, or process as JSON Lines directly.