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diff --git a/cgi.html b/cgi.html deleted file mode 100644 index e1c210b..0000000 --- a/cgi.html +++ /dev/null @@ -1,268 +0,0 @@ -<!DOCTYPE html> -<html lang=en> - <head> - <title>Server-Side Scripting with CGI</title> - <meta charset="utf-8"/> - <link rel="shortcut icon" href="favicon.ico" type="image/x-icon" /> - <link rel='stylesheet' type='text/css' href='style.css'> - <meta name="viewport" content="width=device-width, initial-scale=1"> - <link rel='alternate' type='application/rss+xml' title='Land Chad RSS' href='/rss.xml'> - </head> -<body> - <header><h1>Server-Side Scripting with CGI</h1></header> - <nav></nav> - <main> - <p> - The basic website tutorial here describes how to set up a static - website — one that just serves HTML files saved on your server, - and until you change something manually, the same content will be served - each time a given page is requested. This is perfectly enough for most - personal website needs. This is how blogs should be implemented, instead - of relying on bloatware like WordPress! - </p> - - <p> - But sometimes you genuinely <i>do</i> need something more. You need your - website to serve different contents depending on the time, on who the - requester is, on the contents of a database, or maybe process user input - from a form. - </p> - - <h2>CGI</h2> - <p> - CGI, or the Common Gateway Interface, is a specification to allow you, - the server owner, to program your web server using pretty much any - programming language you might know. The specification is almost as old - as the Internet itself and for a long time CGI scripting was the primary - method of creating dynamic websites. - </p> - - <p> - CGI is a very simple specification indeed. You write a script in your - favorite language, the script receives input about the request in - environment variables, and whatever you print to the standard output - will be the response. Most likely, though, you will want to use a - library for your language of choice that makes a lot of this - request/response handling simpler (e.g. parsing query parameters for - you, setting appropriate headers, etc.). - </p> - - <h3>Limitations of CGI</h3> - <p> - While in theory you could implement any sort of functionality with CGI - scripts, it's going to get difficult managing a lot of separate scripts - if they're supposed to be working in tandem to implement a dynamic - website. If you want to build a full out web application, you'd probably - be better off learning a web framework than gluing together Perl - scripts. - </p> - - <p> - That said, just as most of the web could be replaced with static - websites, much of the remaining non-static web could be replaced with a - few simple scripts, rather than bloated Ruby on Rails or Django - applications. - </p> - - <h2>Let's write a CGI script!</h2> - - <p> - We'll implement a simple example CGI script. I'll use Ruby for this - tutorial, but you'll be able to follow along even if you don't know - Ruby, just treat it as pseudocode then find a CGI library for your - language. - </p> - - <h3>The working example</h3> - - <p> - Our working example will be the Lazy Calculator. Yeah, you're probably - tired of seeing calculator examples in every programming tutorial, but - have you ever implemented one that takes the weekends off? - </p> - - <p> - Here's how it will work. When in a browser you submit a request to your - website like - </p> - - <pre><code>example.com/calculator.html?a=10&b=32</code></pre> - - <p> - you will receive a page with the result of the addition of 10 and 32: - 42. - </p> - - <p> - <i>Unless</i> you send your request on a weekend. Then the website will - respond with - </p> - - <pre><code>I don't get paid to work on weekends! Come back Monday.</code></pre> - - <p> - This example will show a few things that CGI scripts can do that you - wouldn't have been able to get using just file hosting in your - web server: - - <ul> - <li> getting inputs from the user; </li> - <li> - getting external information (here just the system time, but you - could imagine instead connecting to a database); - </li> - <li> using the above to create dynamic output. </li> - </ul> - - <h3>The code</h3> - - <p> - Here's an implementation of the lazy calculator as a Ruby CGI script: - </p> - - <pre><code>#!/bin/env ruby - -require 'cgi' -require 'date' - -cgi = CGI.new -today = Date::today - -a = cgi["a"].to_i -b = cgi["b"].to_i - -if today.saturday? || today.sunday? - cgi.out do - "I don't get paid to work on weekends! Come back Monday." - end -else - cgi.out do - (a + b).to_s - end -end</code></pre> - - <p> - Let's go through what's happening here. - </p> - - <h3>The shebang line</h3> - <p> - CGI works by pointing your web server to an executable program. A Ruby - or Python script by itself is not immediately executable by a computer. - But on Unix-like systems you can specify the program that will be able - to execute your file in its first line if it starts with <code>#!</code> - (known as the shebang; read more about it on - <a href="https://en.wikipedia.org/wiki/Shebang_(Unix)">Wikipedia</a>). - </p> - - <p> - So if you're going to be using a scripting language, you'll probably - need the appropriate shebang line at the top of your script. If you use - a compiled language, you'll just point your web server to the compiled - executable binary. - </p> - - <h3>Query parameters</h3> - <p> - The next interesting lines of code are where we set the variables - <code>a</code> and <code>b</code>. Here we are getting user inputs from - the request. - </p> - - <p> - In the example request we mentioned above - (<code>example.com/calculator.html?a=10&b=32</code>), the part - starting from the question mark, <code>?a=10&b=32</code>, is the - <i>query string</i>. This is how users can submit parameters with their - web requests. Usually these parameters are set by e.g. a form on your - website, but in our simple example we'll be just manually manipulating - the URL. - </p> - - <p> - The query string contains key-value pairs. The Ruby CGI library makes - them available in the <code>CGI</code> object it provides. We just need - to index it with the desired key, and we'll get the corresponding value. - </p> - - <h3>Wrapping it up</h3> - <p> - The remaining parts of the code should be pretty self-explanatory. We - get today's date, check if it's a Saturday or a Sunday, and depending on - that, we instruct the CGI library to output either the answer, or a - "come back later" message. - </p> - - <p> - The Ruby library by default returns an HTML response, so we really - should have wrapped our outputs in some <code>html</code>, - <code>body</code>, etc. tags. Alternatively, we could have specified - that the response is just plain text with - </p> - - <pre><code>cgi.out 'text/plain' do</code></pre> - - <p> - In general, your CGI library will probably have ways of specifying all - sorts of HTTP response headers, like status code, content type, etc. - </p> - - <h2>Making it work</h2> - <p> - We have a CGI script, now let's point our web server to it. - </p> - - <h3>Installing FastCGI</h3> - - <p> - If you're using Nginx, install <code>fcgiwrap</code>: - </p> - - <pre><code>apt install fcgiwrap</code></pre> - - <p> - This installs the necessary packages for Nginx to use FastCGI — a - layer between your web server and CGI script that allows for faster - handling of scripts than if the web server had to handle it all by - itself. - </p> - - <p> - Other web servers will probably have a similarly simple way of enabling - FastCGI, or you can look into other methods for launching CGI scripts. - </p> - - <h3>Nginx configuration</h3> - <p> - In the configuration file for your website, add something like the - following: - </p> - -<pre><code>location /calculator.html { - include fastcgi_params; - fastcgi_param SCRIPT_FILENAME /usr/local/bin/lazy-calculator.rb; - fastcgi_param QUERY_STRING $query_string; - fastcgi_pass unix:/run/fcgiwrap.socket; -}</code></pre> - - <p> - <code>fastcgi_param</code> directives specify various parameters for - FastCGI. <code>SCRIPT_FILENAME</code> should point to your executable. - For <code>QUERY_STRING</code>, we just copy Nginx's - <code>$query_string</code> variable. You might want to pass other - information to your CGI script as well, see for example - <a href="https://wiki.debian.org/nginx/FastCGI">the Debian wiki</a> for - a more detailed example, including pointing to an entire directory of - CGI scripts, rather than adding each one by hand to your web server - config. - </p> - - <h2>Contribution</h2> - <ul> - <li>Martin Chrzanowski -- <a - href="https://m-chrzan.xyz">website</a>, <a href="https://m-chrzan.xyz/donate.html">donate</a></li> - </ul> - </main> - <footer><a href="https://landchad.net">LandChad.net</a></br>Because Everyone should be an Internet LandChad.</br><a href="index.html"><li><img src="pix/chad.gif" alt="chad"></li></a><a href="rss.xml"><li><img src="pix/rss.svg" alt="RSS"></li></a><a href="donate-bitcoin.html"><li><img src="pix/btc.svg" alt="BTC"></li></a><a href="donate-monero.html"><li><img src="pix/xmr.svg" alt="XMR"></li></a><a href="https://github.com/lukesmithxyz/landchad"><li><img src="pix/git.svg" alt="Github"></li></a></footer> -</body> -</html> |