JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III SCRIPTING LANGUAGES Previous Question Paper (August/September - 2021 - R18)

Ruby is a case-sensitive, object-oriented language with a flexible lexical and syntactic structure. Lexically, Ruby source code is interpreted as UTF-8 by default. It uses whitespace for readability, but unlike Python, it does not use indentation to define blocks; instead, it uses keywords like do...end or begin...end. Identifiers follow specific conventions: local variables start with a lowercase letter or underscore, instance variables with @, class variables with @@, and global variables with $.

Syntactically, Ruby is highly expressive and emphasizes programmer productivity. It supports optional parentheses for method calls, allowing for a natural language style. Statements are typically terminated by newlines or semicolons. Blocks of code are first-class citizens, often passed to methods using yield or as Proc objects. The language supports various literals for strings, arrays, and hashes, and utilizes symbols (:symbol) for efficient identification.

Ruby provides the cgi library to facilitate the creation of Common Gateway Interface (CGI) scripts. To write a CGI script, one must include the cgi module, instantiate a CGI object, and output the necessary HTTP headers followed by the HTML content. The script must be executable and reside in the server's cgi-bin directory.

Example of a basic Ruby CGI script:

#!/usr/bin/ruby
require 'cgi'
cgi = CGI.new("html4")
puts cgi.header
cgi.out do
  cgi.html do
    cgi.head { cgi.title { "CGI Script" } } +
    cgi.body { cgi.h1 { "Hello from Ruby CGI!" } }
  end
end

In this script, cgi.header generates the required Content-Type header, and the cgi.out method simplifies the generation of HTML tags by providing a block-based syntax for nesting elements.