如何在使用Ruby的OpenUri下载之前获取HTTP头 [英] How to get HTTP headers before downloading with Ruby's OpenUri

问题描述

我目前正在使用OpenURI在Ruby中下载文件。不幸的是，似乎无法在不下载完整文件的情况下获取HTTP标头：

I am currently using OpenURI to download a file in Ruby. Unfortunately, it seems impossible to get the HTTP headers without downloading the full file:

open(base_url,
  :content_length_proc => lambda {|t|
    if t && 0 < t
      pbar = ProgressBar.create(:total => t)
  end
  },
  :progress_proc => lambda {|s|
    pbar.progress = s if pbar
  }) {|io|
    puts io.size
    puts io.meta['content-disposition']
  }

运行上面的代码显示它首先下载完整文件，然后才打印出我需要的标题。

Running the code above shows that it first downloads the full file and only then prints the header I need.

有没有办法获得下载完整文件之前的标题，如果标题不是我期望的标题，我可以取消下载吗？

Is there a way to get the headers before the full file is downloaded, so I can cancel the download if the headers are not what I expect them to be?

推荐答案

看起来我想要的是不可能使用OpenURI，至少不是，正如我所说，没有先加载整个文件。

It seems what I wanted is not possible to archieve using OpenURI, at least not, as I said, without loading the whole file first.

我能做什么我想使用Net :: HTTP的 request_get

I was able to do what I wanted using Net::HTTP's request_get

这里有一个例子：

http.request_get('/largefile.jpg') {|response|
  if (response['content-length'] < max_length)
    response.read_body do |str|   # read body now
      # save to file
    end
  end
}

请注意，这仅在使用块时有效，如下所示：

Note that this only works when using a block, doing it like:

response = http.request_get('/largefile.jpg')

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