Programming CGI in C
What is CGI?
CGI stands for Common Gateway Interface, it enables web-server to provide dynamic web-page to clients. When client sends request(usually GET, POST method) to server, web-server makes a process to run the requested data. Then send the result back to client.
How to Programming CGI?
[Step1] Make process by using fork( ). Also open pipes.
[Step 2] Execute CGI in child process.
fd = open(//temporary file to record cgi result);pipe(tubes);if ((cgi_pid = fork())== 0) // child process
{
close(tubes[1]);
dup2(tubes[0], 0);
execve(args[0], args, env);
}
- args[0] has to be a path of cgi program or cgi script. Such as “/usr/local/bin/php-cgi”
- args[1] has to be a path of cgi file . If it script it has to be NULL.
- args[2] == NULL
- env has parsed request and some more variables according to RFC3875
Meta-variables with names beginning with "HTTP_" contain values read from the client request header fields, if the protocol used is HTTP. The HTTP header field name is converted to upper case, has all occurrences of "-" replaced with "_" and has "HTTP_" prepended to give the meta-variable name.[STEP 3] Pass requested data through pipe in Parent Process.
CGI will give result to web-server and web-server will make response based on this result.
