cgi

CGI (Common Gate Interface)

Doc generation

Two lines at least must be sent to the client:

First line
- a full doc with MIME type Content-type: text/html for HTML doc, or Content-type: text/plain for ASCII text
- a reference Location: /dir1/dir2/myfile.html, or Location: gopher://httprules.foobar.org/
Second line - a blank line

Example

#include <iostream.h>

main()
{
cout << "Content-type: text/html\n\n"; // 2nd \n is for the 2nd line
cout << "Hello, World!";

return(0);
}

test

Communication btwn Doc and CGI Script

CGI uses environment variables to send your script its parameters:

QUERY_STRING

in URL format: space change to '+'
special characters in %xx hexadecimal encoding

PATH_INFO

<a href="/cgi/foobar/lang=eng">foobar</a>

Methods to Access Form Inputs

    <FORM ACTION="http://www.csie.ntu.edu.tw/~your_hd/hello.exe" METHOD=GET>
                                     |                      |
                               your ip address         your script

form fields are encoded as name/value pairs, separated by "&"
all spaces are encoded as "+"

GET

encoded input in QUERY_STRING
form fields are encoded as name/value pairs:
- name1~value1&name2~value2 ...

POST

encoded input in stdin (standard input)
should use CONTENT_LENGTH to determine data length
form fields are encoded as name/value pairs:
- name1=value1&name2=value2 ...

Resources