artem-cliqz / robotstxt

The robots.txt exclusion protocol implementation for Go language #golang

What

This is a robots.txt exclusion protocol implementation for Go language (golang).

Build

To build and run tests run go test in source directory.

Usage

As usual, no special installation is required, just

import "github.com/temoto/robotstxt"

run go get and you're ready.

1. Parse

First of all, you need to parse robots.txt data. You can do it with functions FromBytes(body []byte) (*RobotsData, error) or same for string:

robots, err := robotstxt.FromBytes([]byte("User-agent: *\nDisallow:"))
robots, err := robotstxt.FromString("User-agent: *\nDisallow:")

As of 2012-10-03, FromBytes is the most efficient method, everything else is a wrapper for this core function.

There are few convenient constructors for various purposes:

• FromResponse(*http.Response) (*RobotsData, error) to init robots data

from HTTP response. It does not call response.Body.Close():

robots, err := robotstxt.FromResponse(resp)
resp.Body.Close()
if err != nil {
    log.Println("Error parsing robots.txt:", err.Error())
}

• FromStatusAndBytes(statusCode int, body []byte) (*RobotsData, error) or

FromStatusAndString if you prefer to read bytes (string) yourself. Passing status code applies following logic in line with Google's interpretation of robots.txt files:

• status 2xx -> parse body with FromBytes and apply rules listed there.
• status 4xx -> allow all (even 401/403, as recommended by Google).
• other (5xx) -> disallow all, consider this a temporary unavailability.

2. Query

Parsing robots.txt content builds a kind of logic database, which you can query with (r *RobotsData) TestAgent(url, agent string) (bool).

Explicit passing of agent is useful if you want to query for different agents. For single agent users there is an efficient option: RobotsData.FindGroup(userAgent string) returns a structure with .Test(path string) method and .CrawlDelay time.Duration.

Simple query with explicit user agent. Each call will scan all rules.

allow := robots.TestAgent("/", "FooBot")

Or query several paths against same user agent for performance.

group := robots.FindGroup("BarBot")
group.Test("/")
group.Test("/download.mp3")
group.Test("/news/article-2012-1")

3. Choose pattern matcher

regexp.Regexp object caches one matching machine per concurrently matched goroutine. Every machine allocates 32+KB for every matched expression. With broad crawls and robotx.txt caching it becomes a problem.

Alternative matcher that supports only "*" and "$" symbols can be used by setting RobotsPatternMatcherType = GLOB_MATCHER

Who

Honorable contributors (in undefined order):

• Ilya Grigorik (igrigorik)
• Martin Angers (PuerkitoBio)
• Micha Gorelick (mynameisfiber)

Initial commit and other: Sergey Shepelev [email protected]