Linux / Unix: curl Command Pass Host Headers

How do I send a header to my Web server (such as Nginx / Lighttpd / Apache / ISS) on a Apple OS X or Unix or Linux based system using a curl command line option for testing and debugging my web apps or server nodes behind a load balancer?

curl -H 'YOUR-EXTRA-HEADER-HERE' apache-server-ip
curl -H 'YOUR-EXTRA-HEADER-1-HERE' -H 'YOUR-EXTRA-HEADER-2-HERE' www.cyberciti.biz

For example, send Host header to www.cyberciti.biz to get HTML response from 75.126.153.206:80, run:

curl -H 'Host: www.cyberciti.biz' 75.126.153.206:80

This is also useful when 75.126.153.206 has multiple virtual host set. The default is not to response anything when virtual host header is not sent:
$ curl -I 75.126.153.206:80
Sample outputs:

HTTP/1.1 500 Internal Server Error
Server: nginx
Date: Wed, 31 Oct 2012 18:51:03 GMT
Content-Type: text/html
Connection: keep-alive
X-Whom: l1-biz-cyber

Now, sent www.cyberciti.biz as Host header:
$ curl -I -H 'Host: www.cyberciti.biz' 75.126.153.206:80
Sample outputs:

HTTP/1.1 200 OK
Server: nginx
Date: Wed, 31 Oct 2012 18:52:20 GMT
Content-Type: text/html
Connection: keep-alive
X-Whom: l2-com-cyber
Vary: Cookie
Last-Modified: Wed, 31 Oct 2012 18:48:58 GMT
Cache-Control: max-age=98, must-revalidate
X-Galaxy: Andromeda-1
X-Origin-Type: DynamicViaDAL

You can use this command to test Apache server node behind a load balancer (only work with your own VLAN/LAN setup):

## see if 192.168.1.11:95 apache node #1 is working or not ##
curl -I --header 'Host: www.cyberciti.biz' 'http://192.168.1.11:95/'

Sample outputs:

HTTP/1.1 200 OK
X-Whom: l1-com-cyber
Vary: Cookie
Last-Modified: Wed, 31 Oct 2012 18:54:00 GMT
Cache-Control: max-age=77, must-revalidate
Content-type: text/html
Date: Wed, 31 Oct 2012 18:57:43 GMT
Server: lighttpd

This option can be used multiple times to add/replace/remove multiple headers:

curl www.cyberciti.biz \ 
-H "Accept-Language: en" \ 
-H "Host www.cyberciti.biz" \ 
-H "User-Agent: curl"

References

See curl command man page for more options:
$ man curl