HTTP protocol is a stateless protocol. For a commercial website, it is required to maintain session information among different pages. For example, one user registration ends after completing many pages. How to maintain user's session information across all the web pages?In many situations, using cookies is the most efficient method of remembering and tracking preferences, purchases, commissions, and other information required for better visitor experience or site statistics.How It Works?Your server sends some data to the visitor's browser in the form of a cookie. The browser may accept the cookie. If it does, it is stored as a plain text ... Read More

Drop Down Box is used when we have many options available but only one or two will be selected.ExampleHere is example HTML code for a form with one drop down box − Maths Physics OutputThe result of this code is the following form −Below is dropdown.py script to handle input given by web browser.#!/usr/bin/python # Import modules for CGI handling import cgi, cgitb # Create instance of FieldStorage form = cgi.FieldStorage() # Get data from fields if form.getvalue('dropdown'):    subject = form.getvalue('dropdown') else:    subject = "Not entered" print "Content-type:text/html\r\r" print "" print "" print "Dropdown Box ... Read More

TEXTAREA element is used when multiline text has to be passed to the CGI Program.ExampleHere is example HTML code for a form with a TEXTAREA box − Type your text here... The result of this code is the following form −Below is textarea.cgi script to handle input given by web browser −#!/usr/bin/python # Import modules for CGI handling import cgi, cgitb # Create instance of FieldStorage form = cgi.FieldStorage() # Get data from fields if form.getvalue('textcontent'):    text_content = form.getvalue('textcontent') else:    text_content = "Not entered" print "Content-type:text/html\r\r" print "" print ""; print "Text Area - Fifth ... Read More

Radio Buttons are used when only one option is required to be selected.ExampleHere is example HTML code for a form with two radio buttons − Maths Physics The result of this code is the following form −Below is radiobutton.py script to handle input given by web browser for radio button −#!/usr/bin/python # Import modules for CGI handling import cgi, cgitb # Create instance of FieldStorage form = cgi.FieldStorage() # Get data from fields if form.getvalue('subject'):    subject = form.getvalue('subject') else:    subject = "Not set" print "Content-type:text/html\r\r" print "" print "" print "Radio - Fourth CGI Program" ... Read More

Checkboxes are used when more than one option is required to be selected.ExampleHere is example HTML code for a form with two checkboxes − Maths Physics OutputThe result of this code is the following form −Below is checkbox.cgi script to handle input given by web browser for checkbox button.#!/usr/bin/python # Import modules for CGI handling import cgi, cgitb # Create instance of FieldStorage form = cgi.FieldStorage() # Get data from fields if form.getvalue('maths'):    math_flag = "ON" else:    math_flag = "OFF" if form.getvalue('physics'):    physics_flag = "ON" else:    physics_flag = "OFF" print "Content-type:text/html\r\r" print "" ... Read More

A generally more reliable method of passing information to a CGI program is the POST method. This packages the information in exactly the same way as GET methods, but instead of sending it as a text string after a ? in the URL it sends it as a separate message. This message comes into the CGI script in the form of the standard input.ExampleBelow is same hello_get.py script which handles GET as well as POST method.#!/usr/bin/python Import modules for CGI handling import cgi, cgitb # Create instance of FieldStorage form = cgi.FieldStorage() # Get data from fields first_name = form.getvalue('first_name') ... Read More

The GET method sends the encoded user information appended to the page request. The page and the encoded information are separated by the ? character as follows −http://www.test.com/cgi-bin/hello.py?key1=value1&key2=value2The GET method is the default method to pass information from browser to web server and it produces a long string that appears in your browser's Location:box. Never use GET method if you have password or other sensitive information to pass to the server.The GET method has size limitation: only 1024 characters can be sent in a request string. The GET method sends information using QUERY_STRING header and will be accessible in your ... Read More

All the CGI programs have access to the following environment variables. These variables play an important role while writing any CGI program.Sr.No.Variable Name & Description1CONTENT_TYPEThe data type of the content. Used when the client is sending attached content to the server. For example, file upload.2CONTENT_LENGTHThe length of the query information. It is available only for POST requests.3HTTP_COOKIEReturns the set cookies in the form of key & value pair.4HTTP_USER_AGENTThe User-Agent request-header field contains information about the user agent originating the request. It is name of the web browser.5PATH_INFOThe path for the CGI script.6QUERY_STRINGThe URL-encoded information that is sent with GET method ... Read More

Sr.No.Example & Description1R(?#comment)Matches "R". All the rest is a comment2R(?i)ubyCase-insensitive while matching "uby"3R(?i:uby)Same as above4rub(?:y|le))Group only without creating \1 backreference

Literal charactersSr.No.Example & Description1pythonMatches beginning of line.Character classesSr.No.Example & Description1[Pp]ythonMatch "Python" or "python"2rub[ye]Match "ruby" or "rube"3[aeiou]Match any one lowercase vowel4[0-9]Match any digit; same as [0123456789]5[a-z]Match any lowercase ASCII letter6[A-Z]Match any uppercase ASCII letter7[a-zA-Z0-9]Match any of the above8[^aeiou]Match anything other than a lowercase vowel9[^0-9]Match anything other than a digitSpecial Character ClassesSr.No.Example & Description1.Match any character except newline2\dMatch a digit: [0-9]3\DMatch a nondigit: [^0-9]4\sMatch a whitespace character: [ \t\r\f]5\SMatch nonwhitespace: [^ \t\r\f]6\wMatch a single word character: [A-Za-z0-9_]7\WMatch a nonword character: [^A-Za-z0-9_]Repetition CasesSr.No.Example & Description1ruby?Match "rub" or "ruby": the y is optional2ruby*Match "rub" plus 0 or more ys3ruby+Match "rub" plus 1 or more ... Read More