Description
The package provides a simple ‘robotstxt’ class and accompanying methods to parse and check ‘robots.txt’ files. Data fields are provided as data frames and vectors. Permissions can be checked by providing path character vectors and optional bot names.
Robots.txt files
Robots.txt files are a way to kindly ask webbots, spiders, crawlers, wanderers and the like to access or not access certain parts of a webpage. The de facto ‘standard’ never made it beyond a informal “Network Working Group INTERNET DRAFT”. Nonetheless, the use of robots.txt files is widespread (e.g. https://en.wikipedia.org/robots.txt, https://www.google.com/robots.txt) and bots from Google, Yahoo and the like will adhere to the rules defined in robots.txt files - although, their interpretation of those rules might differ (e.g. rules for googlebot).
As the name of the files already suggests robots.txt files are plain
text and always found at the root of a domain. The syntax of the files
in essence follows a fieldname: value scheme with optional
preceding user-agent: ... lines to indicate the scope of
the following rule block. Blocks are separated by blank lines and the
omission of a user-agent field (which directly corresponds to the HTTP
user-agent field) is seen as referring to all bots. #
serves to comment lines and parts of lines. Everything after
# until the end of line is regarded a comment. Possible
field names are: user-agent, disallow, allow, crawl-delay, sitemap, and
host.
Let us have an example file to get an idea how a robots.txt file
might look like. The file below starts with a comment line followed by a
line disallowing access to any content – everything that is contained in
root (“/”) – for all bots. The next block concerns GoodBot
and NiceBot. Those two get the previous permissions lifted by being
disallowed nothing. The third block is for PrettyBot. PrettyBot likes
shiny stuff and therefor gets a special permission for everything
contained in the “/shinystuff/” folder while all other
restrictions still hold. In the last block all bots are asked to pause
at least 5 seconds between two visits.
# this is a comment
# a made up example of an robots.txt file
Disallow: /
User-agent: GoodBot # another comment
User-agent: NiceBot
Disallow:
User-agent: PrettyBot
Allow: /shinystuff/
Crawl-Delay: 5For more information have a look at: http://www.robotstxt.org/norobots-rfc.txt, where the robots.txt file ‘standard’ is described formally. Valuable introductions can be found at http://www.robotstxt.org/robotstxt.html as well as at https://en.wikipedia.org/wiki/Robots_exclusion_standard - of cause.
Fast food usage for the uninterested
library(robotstxt)
paths_allowed("http://google.com/")
## [1] TRUE
paths_allowed("http://google.com/search")
## [1] FALSEExample Usage
First, let us load the package. In addition we load the dplyr package
to be able to use the magrittr pipe operator %>% and
some easy to read and remember data manipulation functions.
library(robotstxt)
library(dplyr)object oriented style
The first step is to create an instance of the robotstxt class
provided by the package. The instance has to be initiated via providing
either domain or the actual text of the robots.txt file. If only the
domain is provided, the robots.txt file will be downloaded
automatically. Have a look at ?robotstxt for descriptions
of all data fields and methods as well as their parameters.
rtxt <- robotstxt(domain="wikipedia.org")rtxt is of class robotstxt.
class(rtxt)
## [1] "robotstxt"Printing the object lets us glance at all data fields and methods in
rtxt - we have access to the text as well as all common
fields. Non-standard fields are collected in other.
rtxt
## $text
## [1] "#\n# robots.txt for http://www.wikipedia.org/ and friends\n#\n# Please note: There are a lot of pages on this site, and there are\n# some misbehaved spiders out there that go _way_ too fast. If you're\n# irresponsible, your access to the site may be blocked.\n#\n\n# advertising-related bots:\nUser-agent: Mediapartners-Google*\n\n[... 653 lines omitted ...]"
##
## $domain
## [1] "wikipedia.org"
##
## $robexclobj
## <Robots Exclusion Protocol Object>
## $bots
## [1] "Mediapartners-Google*" "IsraBot" "Orthogaffe" "UbiCrawler"
## [5] "DOC" "Zao" "" "[... 28 items omitted ...]"
##
## $comments
## line comment
## 1 1 #
## 2 2 # robots.txt for http://www.wikipedia.org/ and friends
## 3 3 #
## 4 4 # Please note: There are a lot of pages on this site, and there are
## 5 5 # some misbehaved spiders out there that go _way_ too fast. If you're
## 6 6 # irresponsible, your access to the site may be blocked.
## 7
## 8 [... 173 items omitted ...]
##
## $permissions
## field useragent value
## 1 Disallow Mediapartners-Google* /
## 2 Disallow IsraBot
## 3 Disallow Orthogaffe
## 4 Disallow UbiCrawler /
## 5 Disallow DOC /
## 6 Disallow Zao /
## 7
## 8 [... 370 items omitted ...]
##
## $crawl_delay
## [1] field useragent value
## <0 rows> (or 0-length row.names)
##
## $host
## [1] field useragent value
## <0 rows> (or 0-length row.names)
##
## $sitemap
## [1] field useragent value
## <0 rows> (or 0-length row.names)
##
## $other
## [1] field useragent value
## <0 rows> (or 0-length row.names)
##
## $check
## function (paths = "/", bot = "*")
## {
## spiderbar::can_fetch(obj = self$robexclobj, path = paths,
## user_agent = bot)
## }
## <bytecode: 0x12f9629b0>
## <environment: 0x12f965c10>
##
## attr(,"class")
## [1] "robotstxt"Checking permissions works via rtxt’s check
method by providing one or more paths. If no bot name is provided
"*" - meaning any bot - is assumed.
# checking for access permissions
rtxt$check(paths = c("/","api/"), bot = "*")
## [1] TRUE FALSE
rtxt$check(paths = c("/","api/"), bot = "Orthogaffe")
## [1] TRUE TRUE
rtxt$check(paths = c("/","api/"), bot = "Mediapartners-Google* ")
## [1] TRUE FALSEfunctional style
While working with the robotstxt class is recommended the checking can be done with functions only as well. In the following we (1) download the robots.txt file; (2) parse it and (3) check permissions.
r_text <- get_robotstxt("nytimes.com")
r_parsed <- parse_robotstxt(r_text)
r_parsed
## $useragents
## [1] "*" "Mediapartners-Google" "AdsBot-Google" "adidxbot"
##
## $comments
## [1] line comment
## <0 rows> (or 0-length row.names)
##
## $permissions
## field useragent value
## 1 Allow * /ads/public/
## 2 Allow * /svc/news/v3/all/pshb.rss
## 3 Disallow * /ads/
## 4 Disallow * /adx/bin/
## 5 Disallow * /archives/
## 6 Disallow * /auth/
## 7 Disallow * /cnet/
## 8 Disallow * /college/
## 9 Disallow * /external/
## 10 Disallow * /financialtimes/
## 11 Disallow * /idg/
## 12 Disallow * /indexes/
## 13 Disallow * /library/
## 14 Disallow * /nytimes-partners/
## 15 Disallow * /packages/flash/multimedia/TEMPLATES/
## 16 Disallow * /pages/college/
## 17 Disallow * /paidcontent/
## 18 Disallow * /partners/
## 19 Disallow * /restaurants/search*
## 20 Disallow * /reuters/
## 21 Disallow * /register
## 22 Disallow * /thestreet/
## 23 Disallow * /svc
## 24 Disallow * /video/embedded/*
## 25 Disallow * /web-services/
## 26 Disallow * /gst/travel/travsearch*
## 27 Disallow Mediapartners-Google /restaurants/search*
## 28 Disallow AdsBot-Google /restaurants/search*
## 29 Disallow adidxbot /restaurants/search*
##
## $crawl_delay
## [1] field useragent value
## <0 rows> (or 0-length row.names)
##
## $sitemap
## field useragent value
## 1 Sitemap * http://spiderbites.nytimes.com/sitemaps/www.nytimes.com/sitemap.xml.gz
## 2 Sitemap * http://www.nytimes.com/sitemaps/sitemap_news/sitemap.xml.gz
## 3 Sitemap * http://spiderbites.nytimes.com/sitemaps/sitemap_video/sitemap.xml.gz
##
## $host
## [1] field useragent value
## <0 rows> (or 0-length row.names)
##
## $other
## [1] field useragent value
## <0 rows> (or 0-length row.names)
paths_allowed(
paths = c("images/","/search"),
domain = c("wikipedia.org", "google.com"),
bot = "Orthogaffe"
)
## wikipedia.org google.com
## [1] TRUE FALSE