CODEWITHSUNDEEP
ruby
randy newfield
randy newfield

Reputation: 1221

Downloading a specific part of a file from a http server

How would I emulate the behavior of curl -r (range) in a ruby script without using backticks or other methods to run the curl binary?

I know how to start from the beginning of a file and save a file in chunks, but how would I start at a specific portion of the remote file then download for X bytes?

Say the file was 1000 bytes long, and I wanted to start at byte 60 and download 20 bytes from that point (finishing at 80). How would this be done?

Is there a gem wrapper around curl which is cross platform, or another gem that provides this support? Or is this possible with the standard open-uri or net::http libraries?

Thanks!

Upvotes: 0

Views: 112

Answers (1)

Jordan Running
Jordan Running

Reputation: 106147

You can do this with any library that lets you set request headers (all curl -r does is set the Range header), which should be pretty much any HTTP library. Net::HTTP, for its part, has a set_range convenience method that takes as arguments either a single Range object (e.g. 60...80) or a start index and length:

require "net/http"
require "uri"

url = URI.parse("http://example.com/foo")
req = Net::HTTP::Get.new(url.path)

req.set_range(60, 20)

res = Net::HTTP.new(url.host, url.port).start do |http|
  http.request(req)
end
puts res.body

Upvotes: 1

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