$ curl -I -f "http://json.org/example"
HTTP/1.1 200 OK
Date: Tue, 10 Jun 2014 20:01:02 GMT
Server: Apache
...
Ah! but it does not provide the / at the tail. We get a 404.
$ curl -I "http://json.org/example/"
HTTP/1.1 404 Not Found
Date: Tue, 10 Jun 2014 20:01:15 GMT
Server: Apache
...
echo $? will return 0 in both the case.
What if we are using it inside a script and want the process to fail on non success HTTP status?
Use –f option
$ curl -I -f "http://json.org/example/"
curl: (22) The requested URL returned error: 404
$ echo $?
22
The man says:
-f, --fail
(HTTP) Fail silently (no output at all) on server errors. This is mostly done to better enable scripts etc to better deal with failed attempts. In
normal cases when a HTTP server fails to deliver a document, it returns an HTML document stating so (which often also describes why and more). This
flag will prevent curl from outputting that and return error 22.
This method is not fail-safe and there are occasions where non-successful response codes will slip through, especially when authentication is
involved (response codes 401 and 407).
Note: -I is better option to user than --request HEAD, as --request HEAD request will hang for a while :)
