Echo curl request header & body without sending it?

Question

With the curl command line tool, is it possible to echo, print, or view the request, and not send it? Sort of like a -n option? I would like to see the request header & body, and anything else that's included. Is there anything else that's sent besides header & body?

Solution 1

Let me second the suggestion to use 'nc' (netcat) to get to see all the details without sending anything offsite to anywhere.

But you can also get all the details for any curl command line request by using the --trace or --trace-ascii commands that can dump all incoming and outgoing data and requests for inspection.

These options have the additional benefit in comparison to 'nc' that they can show the protocol details even for HTTPS operations and with "real" command lines etc.

Solution 2

A HTTP request is constructed with a request line, headers and a body.

curl does not seem to have a flag to do a "dry-run". Depending on your needs, you might be able to see what you want using netcat as a proxy:

$ nc -l localhost 8000 &
[1] 3150
$ curl --proxy localhost:8000 --silent --max-time 1 http://www.stackoverflow.com
GET http://www.stackoverflow.com HTTP/1.1
User-Agent: curl/7.19.7 (x86_64-pc-linux-gnu) libcurl/7.19.7 OpenSSL/0.9.8k zlib/1.2.3.3 libidn/1.15
Host: www.stackoverflow.com
Accept: */*
Proxy-Connection: Keep-Alive

[1]+  Done                    nc -l localhost 8000

Comments

[Ciro Santilli OurBigBook.com]

--trace - for stdout.

[Randall]

How did you get the netcat to terminate cleanly ([1]+ Done)? In my test, I'm finding I need to Ctrl-C out of it, then fg it, and then Ctrl-D. It works, but seems a clunky way to exit the netcat.

[Randall]

Ah - it looks like the key was the --max-time 1 flag, to time it out, with the --silent to suppress the time out message. I omitted those both initially.

[Edoardo]

...of course this will not work with HTTPS, it shows only CONNECT www.stackoverflow.com:443 HTTP/1.1 and Proxy-Connection: Keep-Alive