How do I only read the header for a URL in Ruby?

Question

How do I read the header only in Ruby? I tried some of the options in the documentation for open but it still reads the entire file.

http://ruby-doc.org/stdlib-2.0.0/libdoc/open-uri/rdoc/OpenURI/OpenRead.html#method-i-open

irb(main):153:0> html=open(url, :content_length_proc => lambda {|len| p len  })
177602
=> #<Tempfile:C:/Users/Chloe/AppData/Local/Temp/open-uri20140220-8496-o5zlda>

I want something like curl -I or wget --spider.

Ok found two ways!

open(url){|f| f.meta['content-length']}

Net::HTTP.start(uri.host) {|http| http.head(uri.path)['content-length']}

I like the first as it's simpler and doesn't require creating then parsing a URI object.

try http://stackoverflow.com/questions/17900207/getting-headers-from-a-ruby-nethttp-request-before-making-the-request — Paritosh Piplewar, Feb 20 '14 at 20:59
Or http://stackoverflow.com/questions/17454956/get-http-headers-before-downloading-with-open-uri-ruby — Phrogz, Feb 20 '14 at 21:12
@ParitoshPiplewar That question is to get the REQUEST headers, not the RESPONSE headers. — Chloe, Feb 20 '14 at 22:44

score 3 · Accepted Answer · answered Feb 20 '14 at 21:12

3

As far as I'm aware this isn't possible with OpenURI but is with Net:HTTP (this may have changed). See this answer:

Get HTTP Headers before downloading with open-uri (Ruby)

which suggests you use Net::HTTP's request_get method.

answered Feb 20 '14 at 21:12

Richard Jordan

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If you're just going to link to another answer, I recommend that you make a comment, not an answer. – Phrogz Feb 20 '14 at 21:13
well i can copy the text of that answer but it seems pointless – Richard Jordan Feb 20 '14 at 21:14
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I agree. Which is why I made a comment and voted to close this question as a duplicate. – Phrogz Feb 20 '14 at 21:14

score 1 · Answer 2 · answered Feb 20 '14 at 21:13

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If you're open to trying a gem, httpclient is great for that:

require 'httpclient'
HTTPClient.new.head('http://google.com')

answered Feb 20 '14 at 21:13

Abdo

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I think the solution you suggested would execute a HEAD request and not retrieve the headers of the request. To retrieve the header with httpclient, you should do something like `HTTPClient.new.get('http://google.com').headers`. However, this would require to read the all response. – Raphael Pr Jan 02 '20 at 15:05

How do I only read the header for a URL in Ruby?

2 Answers2