Passing HTML form data to C script and CGI standard behavior

Question

I'm trying to make a login script in C. I want to know, how I can pass the HTML form data to my back-end c script. I'm new to C (coming from perl)

Just do this?

<form action="test.c"> or <form action="test.a"> 

How can the script explicitly differ between username and password? Earlier, I just had to do this (in perl):

$username = $cgi->param("username");

How can I do this now in C. I'm trying to avoid using CGI at all.

Edit 1:

1. It seems I also need to know, how CGI basically works (in short). I'm guessing, the browser is a sort-of compiler for CGI? if not, then is it apache?

2. Since C is not a interpreted language, how does CGI work with C? In perl, I could simply do:

   #!/usr/bin/perl
   print "Content-type: text/html\n\n";
   print "Hello, World.";
   

How do I do this in C?

Edit2: Ok, I went over to previously answered questions under the cgi tag here on stackoverflow.

This seems to be the most voted one: What is Common Gateway Interface (CGI)?

But it still doesn't clear a few things, which I'm asking here.

Since RFC3875 is only a informational doc, and there is no finalized standard.

1. Who implements CGI protocol? Who defines its "standard behavior" on servers such as Apache.

2. How does C files work with CGI in modern environment. Please elaborate using a "Hello World!" as a response to a form submission.

Answer 1

Trying to help you is a bit difficult. Your question, in particular the statement "I'm trying to avoid using CGI at all" implies that you're missing a conceptual overview. In order to 'avoid CGI' you need to replace it with a mechanism to receive, parse and respond to HTTP requests. That would mean (potentially) writing an HTTP server. C is a compiled language. When you wonder if you can do action="test.c" it shows me that you're missing the fact that C isn't an interpreted language.

You could use something like tiny httpd to get you started.

This site about cgi using C will help you. How CGI is implemented ends up being at the discretion of the implementor. A hello world program is as simple as the compiled executable of

#include <stdio.h>
int main(void) {
  printf("Content-Type: text/plain;charset=us-ascii\n\n");
  printf("Hello world\n\n");
  return 0;
}