file-search-on

README

file-search-on

Content-type aware file search with CEL-powered attribute filtering.

file-search-on walks a directory tree and returns files matching a CEL expression evaluated over each file's metadata and content-type-specific attributes. Instead of grepping by name, you can ask things like "all PDFs with more than 10 pages" or "all Markdown files over 500 words whose title starts with 'Draft'".

Features

• First-class Markdown front-matter search — query YAML (---), TOML (+++), and JSON ({ ... }) front-matter directly. Common keys (title, author, tags, categories, draft, date) are promoted to top-level CEL variables, and a generic frontmatter map exposes every other key. See the dedicated section below.
• Pluggable content-type detection — extension-first, with magic-byte fallback. Markdown, JSON, XML, HTML, PDF, and the common image formats (JPEG, PNG, GIF, WebP, SVG, TIFF, BMP) are supported out of the box.
• Rich, type-specific attributes — page count and author for PDFs, title and word count for Markdown, root element for XML, dimensions for images, and more.
• CEL expressions — the full Common Expression Language is available, so you can compose conditions naturally with &&, ||, comparisons, string functions, and so on.
• Parallel walking — files are evaluated across a configurable worker pool (defaults to the number of CPU cores).

Install

Homebrew (macOS / Linux)

brew install richardwooding/tap/file-search-on

The cask is published from this repo on every tagged release to richardwooding/homebrew-tap.

macOS Gatekeeper: the binary isn't yet signed with an Apple Developer ID, so macOS may block it on first run. The cask's post-install hook strips the quarantine xattr automatically. If macOS still blocks it, run:

sudo xattr -dr com.apple.quarantine $(brew --prefix)/bin/file-search-on

Container (Docker / Podman)

OCI images are published to GitHub Container Registry on every tag, with linux/amd64 and linux/arm64 manifests:

docker run --rm -v "$PWD:/work" ghcr.io/richardwooding/file-search-on:latest \
  'is_markdown && draft' -d /work

Pin to a specific version with :vX.Y.Z. The base image is cgr.dev/chainguard/static, so the container has the binary and nothing else (no shell).

Pre-built binaries

Pre-built archives for Linux, macOS, and Windows on amd64 and arm64 are attached to every GitHub Release, along with a checksums.txt you should verify.

From source

Requires Go 1.26.2 or newer.

go install github.com/richardwooding/file-search-on/cmd/file-search-on@latest

Or build from a clone:

git clone https://github.com/richardwooding/file-search-on.git
cd file-search-on
go build -o file-search-on ./cmd/file-search-on

Usage

file-search-on [EXPR] [-d DIR] [-w WORKERS]
file-search-on --list

Flag	Description	Default
EXPR	CEL expression to match files against.	true (matches everything)
-d, --dir	Directory to search.	.
-w, --workers	Number of parallel workers.	number of CPU cores
-l, --list	List supported attributes and registered content types.

Each matching file is printed as <path>\t[<content-type>]\t<size> bytes. The match count is written to stderr so it doesn't pollute pipelines.

Markdown front-matter search

Searching across the front-matter of large note collections, blogs, and documentation sites is a primary use case for this tool. Three formats are recognised, detected by the very first bytes of the file:

Format	Opening	Closing	Common in
YAML	--- line	--- line	Jekyll, Obsidian, Hugo, MkDocs
TOML	+++ line	+++ line	Hugo, Zola
JSON	{ at byte 0	matching }	Hugo, Eleventy

Parsing is lightweight: the front-matter block is read and decoded directly with gopkg.in/yaml.v3, pelletier/go-toml/v2, or encoding/json. The Markdown body is not parsed beyond a single pass for word_count and an H1 title fallback, so this stays fast across thousands of files.

Six commonly-used keys are promoted to first-class CEL variables; everything else is reachable through the generic frontmatter map.

CEL variable	Type	Notes
title	string	Front-matter title overrides the H1 fallback.
author	string	From front-matter.
tags	list<string>	A bare string (tags: solo) is wrapped as a single-element list.
categories	list<string>	Same coercion as tags.
draft	bool	Defaults to false when missing.
date	timestamp	Native TOML dates and common YAML/JSON string layouts (RFC3339, YYYY-MM-DD, etc.) are accepted.
frontmatter	map<string, dyn>	Full parsed map. Reach any custom key with frontmatter.your_key.
frontmatter_format	string	"yaml", "toml", "json", or "" if no front-matter was present.

Front-matter examples

Find drafts in your blog:

file-search-on 'is_markdown && draft' -d ./content

Find Markdown tagged go and not draft:

file-search-on 'is_markdown && "go" in tags && !draft' -d ./posts

Find published posts from 2024 onward:

file-search-on 'is_markdown && date >= timestamp("2024-01-01T00:00:00Z")'

Reach a custom front-matter key (e.g. category: essay):

file-search-on 'is_markdown && frontmatter.category == "essay"'

Find files in a specific front-matter format:

file-search-on 'is_markdown && frontmatter_format == "toml"'

Combine front-matter with structural attributes — long, tagged, non-draft posts:

file-search-on 'is_markdown && word_count > 1000 && "longread" in tags && !draft'

Examples

Find all Markdown files larger than 500 words:

file-search-on 'is_markdown && word_count > 500' -d ./docs

Find PDFs with more than 10 pages, written by a specific author:

file-search-on 'is_pdf && page_count > 10 && author == "Jane Doe"'

Find all JSON files whose top-level value is an array:

file-search-on 'is_json && json_kind == "array"'

Find images wider than 1920 pixels:

file-search-on 'is_image && img_width > 1920' -d ~/Pictures

Combine paths and types — find HTML files inside a build/ directory:

file-search-on 'is_html && dir.contains("build")'

Available attributes

Common attributes (always present):

Attribute	Type	Description
name	string	Filename
path	string	Full path
dir	string	Parent directory
size	int	File size in bytes
ext	string	File extension, e.g. .md
content_type	string	Detected content type
is_markdown, is_json, is_xml, is_html, is_pdf, is_image, is_text, is_csv, is_epub	bool	Type predicates

Type-specific attributes (zero-valued when not applicable):

Attribute	Type	Source
title	string	Markdown front-matter, then H1; HTML <title>; PDF metadata; EPUB <dc:title>
word_count	int	Markdown body (front-matter excluded), plain text
line_count	int	Plain text
column_count	int	CSV/TSV header row
page_count	int	PDF
author	string	Markdown front-matter, PDF, EPUB <dc:creator>
language	string	EPUB <dc:language>
root_element	string	XML
json_kind	string	"object" or "array"
img_width, img_height	int	Image dimensions in pixels
frontmatter	map<string, dyn>	Full Markdown front-matter map
frontmatter_format	string	"yaml", "toml", "json", or ""
tags, categories	list<string>	Markdown front-matter
draft	bool	Markdown front-matter
date	timestamp	Markdown front-matter

Run file-search-on --list to see the full, up-to-date list along with the registered content types.

MCP server mode

The same binary can run as a Model Context Protocol server, exposing the search to any MCP-compatible client (Claude Desktop, IDE plugins, agents). Stdio transport, no flags:

file-search-on mcp

Two tools are exposed:

Tool	Input	Output
search	expr, dir, workers	matches[] (path, content_type, size) and count
list_attributes	none	schema (common, type_specific, frontmatter) and content_types[]

Empty expr matches everything; empty dir defaults to .. workers falls back to runtime.NumCPU().

Example Claude Desktop entry in claude_desktop_config.json:

{
  "mcpServers": {
    "file-search-on": {
      "command": "file-search-on",
      "args": ["mcp"]
    }
  }
}

Built on github.com/modelcontextprotocol/go-sdk.

Development

go build ./...                                  # build everything
go test -race -coverprofile=coverage.out ./...  # run the test suite
go vet ./...
go fix ./...                                    # apply Go 1.26 modernizers — see below
golangci-lint run

The codebase has three internal packages: internal/content (the pluggable type registry), internal/celexpr (the CEL evaluator and attribute builder), and internal/search (the parallel walker). See CLAUDE.md for an architecture overview and a step-by-step guide to adding a new content type.

Keeping the code modern with go fix

Go 1.26 reintroduced go fix as a code-modernization tool that rewrites your sources to use newer language and standard-library features (slices.Contains, any, min/max, range over integers, sync.WaitGroup.Go, and more).

go fix -diff ./...   # preview the changes
go fix ./...         # apply them
go tool fix help     # list every available fixer

CI runs go fix ./... && git diff --exit-code after every build, so the project stays idiomatic for whichever Go release the toolchain is pinned to. After bumping the Go version, run go fix ./... from a clean working tree and commit the result on its own.

License

MIT