Ruby CGI Method

Ruby's CGI library has various methods to interact with the CGI protocol, helping to handle HTTP requests and responses. Here are some important methods:

new: Creates a new CGI object.

cgi = CGI.new

out: Prints an HTTP header and body to $DEFAULT_OUTPUT ($stdout).

cgi.out do
  "Hello, world!"
end

This will send an HTTP response with "Hello, world!" as the body. You can also add optional parameters to send specific HTTP headers:

cgi.out("text/plain") do
  "Hello, world!"
end

This will send an HTTP response with a Content-Type of "text/plain".

header: Returns a string that can be used as an HTTP header.

header = cgi.header

This will return a basic HTTP header as a string. You can also add optional parameters to specify the content type, status, and other HTTP header values.

params: Returns a hash of all parameters in the request.

params = cgi.params

This will return a hash where the keys are parameter names and the values are arrays of parameter values.

cookies: Returns a hash of all cookies in the request.

cookies = cgi.cookies

This will return a hash where the keys are cookie names and the values are arrays of cookie values.

html: Returns an HTML string.

html = cgi.html do
  cgi.head { cgi.title{"Hello Page"} } +
  cgi.body { cgi.h1 {"Hello, world!"} }
end

This method helps to generate HTML content. Note that the plus operator is used to concatenate the head and body.

print: Prints to $DEFAULT_OUTPUT ($stdout).

cgi.print "Hello, world!"

This will print "Hello, world!" to $stdout, which is usually the web server when running a CGI script.

Remember, the Ruby CGI library is not commonly used for modern web development. Frameworks like Ruby on Rails, Sinatra, or Hanami provide more features and a higher level of abstraction. However, understanding how CGI works can give you a better understanding of how HTTP and web servers work.

CGI methods for form handling in Ruby:

Description: CGI provides methods for handling form submissions, allowing you to retrieve data submitted through HTML forms.

Code example (retrieving form data):

#!/usr/bin/env ruby

require 'cgi'

cgi = CGI.new

# Retrieve form data using CGI methods
user_name = cgi['user_name']
password = cgi['password']

puts "Content-type: text/html\n\n"
puts "<html><body>"
puts "<p>User Name: #{user_name}</p>"
puts "<p>Password: #{password}</p>"
puts "</body></html>"

HTTP methods in Ruby CGI scripts:

Description: CGI scripts can determine the HTTP method (GET, POST, etc.) used in the request using the request_method method.

Code example (checking HTTP method):

#!/usr/bin/env ruby

require 'cgi'

cgi = CGI.new

# Check the HTTP method
http_method = cgi.request_method

puts "Content-type: text/html\n\n"
puts "<html><body>"
puts "<p>HTTP Method: #{http_method}</p>"
puts "</body></html>"

Methods for working with parameters in Ruby CGI:

Description: CGI provides methods for retrieving parameters from the URL query string or form submissions.

Code example (retrieving parameters):

#!/usr/bin/env ruby

require 'cgi'

cgi = CGI.new

# Retrieve parameters from URL query string or form
user_name = cgi['user_name']
password = cgi['password']

puts "Content-type: text/html\n\n"
puts "<html><body>"
puts "<p>User Name: #{user_name}</p>"
puts "<p>Password: #{password}</p>"
puts "</body></html>"

Ruby CGI request and response methods:

Description: CGI provides methods to access information about the request and generate the response.

Code example (accessing request and generating response):

#!/usr/bin/env ruby

require 'cgi'

cgi = CGI.new

# Access request information
user_agent = cgi.user_agent

# Generate response
puts "Content-type: text/html\n\n"
puts "<html><body>"
puts "<p>User Agent: #{user_agent}</p>"
puts "</body></html>"

Handling GET and POST methods in Ruby CGI:

Description: CGI scripts can handle both GET and POST methods, and the method can be determined using request_method.

Code example (handling GET and POST):

#!/usr/bin/env ruby

require 'cgi'

cgi = CGI.new

# Determine HTTP method
http_method = cgi.request_method

# Handle GET or POST accordingly
case http_method
when 'GET'
  # Handle GET parameters
  user_name = cgi['user_name']
when 'POST'
  # Handle POST parameters
  user_name = cgi.params['user_name'].first
end

puts "Content-type: text/html\n\n"
puts "<html><body>"
puts "<p>User Name: #{user_name}</p>"
puts "</body></html>"

Security considerations for CGI methods in Ruby:

Description: CGI scripts should handle user input carefully, validate and sanitize data, and be aware of security considerations to prevent attacks.

Code example (basic input validation):

#!/usr/bin/env ruby

require 'cgi'

cgi = CGI.new

# Validate and sanitize input
user_name = cgi['user_name']
sanitized_name = CGI.escapeHTML(user_name)

puts "Content-type: text/html\n\n"
puts "<html><body>"
puts "<p>Sanitized User Name: #{sanitized_name}</p>"
puts "</body></html>"

Handling redirects with CGI methods in Ruby:
- Description: CGI scripts can issue HTTP redirects using the Location header in the response.
- Code example (performing a redirect):
```
#!/usr/bin/env ruby

require 'cgi'

cgi = CGI.new

# Redirect to a different URL
redirect_url = 'https://example.com'
puts "Location: #{redirect_url}\n\n"
```