Knap

Use Knap CLI to render Markdown templates with variables, filters, and logic.

If not installed: npm install -g knap (requires Node.js 20 or later). Alternatively, use npx knap.

Run knap --help for available commands and options. Discover the language through the CLI's offline reference:

knap help syntax
knap help filters
knap help filter date
knap help tags
knap help tag for

Use the lists to find names, then request individual help for syntax, parameters, and examples with expected output.

Usage

Render a template with JSON variables:

knap render template.md --data article.json -o note.md

Supply a template and data inline:

knap render -t '# {{ title | trim }}' --data-json '{"title":"Hello"}'

Override a variable or pipe JSON data:

knap render template.md --data article.json --set 'title=Custom title'
cat article.json | knap render template.md --data -

Data must be a JSON object; its properties become template variables. --set overrides literal top-level keys with strings. Use JSON for nested objects, arrays, numbers, and booleans.

Choose one template source (file, -t, or stdin) and one data source (--data or --data-json). Only one input can read stdin. Without a template file or -t, Knap reads the template from stdin.

Output defaults to stdout. -o creates parent directories and overwrites the destination after rendering succeeds. Errors exit with status 1; diagnostics go to stderr. Warnings can accompany successful output.

Templates

Use {{ variable }} for values, | for filters, and {% ... %} for logic. For example, save this as template.md:

---
{{ title | yaml_property:"title" }}
{{ tags | yaml_property:"tags" }}
---
# {{ title | trim }}
{% if author %}
By {{ author }}
{% endif %}

{{ content }}

Use yaml_property for complete frontmatter properties so values are quoted and indented correctly. The CLI includes standard filters, but does not supply Web Clipper browser variables, selectors, prompts, or DOM-dependent HTML filters. Supply variables through JSON.

Check a template before rendering:

knap validate template.md

Validation checks syntax, filter names, and static filter arguments without data or file output. It does not check variable existence, runtime values, or dynamic arguments; render with real data to check runtime behavior. Diagnostics go to stderr and include relevant help commands.

Defuddle pipeline

Extract a web page as JSON with Markdown content, then render it into a note:

defuddle parse https://example.com/article --md --json \
  | knap render template.md --data - -o note.md

Defuddle's JSON properties, such as title and content, become template variables directly.

Batch rendering

Create one file per CSV row, JSON array object, or JSON file in a folder:

knap batch template.md --data articles.csv --output-dir notes \
  --filename '{{ title | safe_name }}.md'

Use --data articles.json for an array or --data ./articles for a folder of JSON objects. CSV headers become variable names and values remain strings. Piped data defaults to JSON; add --format csv for piped CSV.

Use --dry-run to validate and list output paths without writing files. Existing files require --overwrite, including during a dry run. Duplicate output names within a batch are errors even with --overwrite.

Filename templates must produce a single filename with its extension, without directories. Use safe_name for data-derived names. Without --filename, Knap preserves source JSON basenames or numbers CSV rows and array items as 1.md, 2.md, and so on.