Carlos León

If want to consume an API that uses sessions using cURL, then probably you will need to make use of cookies. Using cookies with cURL is pretty simple.

I’m going to create a simple web application using [Sinatra] for the example’s sake:

require "rubygems"
require "sinatra"

enable :sessions

get "/" do
  session[:user] # Return whatever stored in session[:user].
end

post "/" do
  session[:user] = params[:user] # Set session[:user] to whatever sent on param.
end

Now, from console:

$ curl -i -X POST -d "name=Carlos" http://localhost:4567
HTTP/1.1 200 OK
Content-Type: text/html;charset=utf-8
Content-Length: 10
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
Set-Cookie: rack.session=BAh7CUkiD3Nlc3Npb25faWQGOgZF...; path=/; HttpOnly
Connection: keep-alive
Server: thin 1.5.1 codename Straight Razor

• The -i flag tells cURL to include the HTTP-header in the output.
  
• The -X flag specifies the request method (It’s GET by default but in our case it’s POST).
  
• The -d flag sends the specified data in the request to the server.

Notice the Set-Cookie header that the server returned: rack.session=BAh7CUkiD3Nlc3Npb25faWQGOgZF...

We’re now going to perform a GET request to the server and also we’re going to send that cookie to the server so that the server knows we’re keeping track of the session because we care (?)

$ curl http://localhost:4567 -b "rack.session=BAh7CUkiD3Nlc3Npb25faWQGOgZF..."
Carlos

If we performed the same request without passing along the cookie the server wouldn’t recognise what session we’re talking about, so the “name” session key is by default unset:

$ curl http://localhost:4567
$

Pretty simple.