Track redirects with curl

I was recently debugging some .htaccess redirects and wanted to know two things:

  1. How was my URL changing as it went through the redirects?
  2. How many redirects occurred?

I quickly got fed up with testing in the browser because of 301/302 redirect caching issues. With my limited curl knowledge I knew I could dump headers and that would show me the redirect code and the URL but figuring out how many hops occurred was frustrating.

I searched around and found this very helpful post by Chris Latta. The curl command from the post introduced me to the fact that curl has basic templating support! I read through man curl and noticed there were other built-in variables besides url_effective, like num_redirects! This was exactly what I wanted. Below is what I eventually ended up with:

curl -LSs -D - -o /dev/null -w 'Final URL: %{url_effective} \nNumber of Redirects: %{num_redirects} '

I added this to my dotfiles as an alias called redirects, here is a sample of what the output looks like:

❯ redirects ""
HTTP/1.1 301 Moved Permanently
Cache-Control: public, max-age=0, must-revalidate
Content-Length: 44
Content-Type: text/plain
Date: Tue, 22 Oct 2019 17:39:10 GMT
Age: 0
Connection: keep-alive
Server: Netlify
X-NF-Request-ID: de179b0f-db8b-401a-97ad-7ce523020763-108626

HTTP/2 200
cache-control: public, max-age=0, must-revalidate
content-type: text/html; charset=UTF-8
date: Tue, 22 Oct 2019 17:39:10 GMT
etag: "3f4bb560fd31e7328aedc7bc08a9c541-ssl"
strict-transport-security: max-age=31536000
age: 0
server: Netlify
x-nf-request-id: de179b0f-db8b-401a-97ad-7ce523020763-108794

Final URL:
Number of Redirects: 1 %

curl might be one of the most important tools I have at my disposal for working with HTTP requests and I feel like I've only begun to scratch the surface of what it can do.

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