PERL/C3/Perl-and-HTML/English-timed

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'Time Narration
00:01 Welcome to the Spoken Tutorial on Perl and HTML.
00:06 In this tutorial, we will learn how to create
  • html pages and
  • CGI module.
00:14 To record this tutorial, I am using:
  • Ubuntu Linux 12.04 operating system
  • Perl 5.14.2
  • Firefox Web Browser
  • Apache HTTP server and
  • 'gedit' Text Editor.
00:31 You can use any text editor of your choice.
00:35 To follow this tutorial, you should have working knowledge of Perl programming.
00:40 If not, then go through the relevant Perl spoken tutorials on the spoken tutorial website.
00:47 Perl programs which are used on the web are called Perl CGI.
00:52 CGI stands for Common Gateway Interface.
00:56 It is an interface to serve client-server web communication.
01:01 CGI.pm is a Perl module that gets installed along with Perl installation which serves the communication.
01:10 CGI.pm has ready to use functions to help developers, to write Perl CGI applications.
01:19 When a file in certain directory is requested from web browser, unlike HTTP server, Perl CGI scripts get executed and send output back to browser to display.
01:33 This function is called CGI and the programs are called CGI scripts.
01:40 CGI programs can be a Perl script, Shell Script, C or C++ program.
01:47 Now, let us see a sample Perl program.
01:50 Switch to the terminal.
01:53 Let me open a file cgiexample.pl in gedit which I have already saved.
02:01 In the cgiexample dot pl file, type the following code as displayed on the screen.
02:08 Let us understand the code now.
02:11 use CGI statement tells Perl that we want to use the CGI.pm module in our program.
02:19 It will load the module and make a set of CGI functions available for our code.
02:26 To start the HTML, we use the method start_html().
02:33 “My Home Page” is the page title given for the web page.
02:38 We can print any HTML tag using the CGI module.
02:43 Heading tags are represented by h1, h2 etc.
02:49 The end_html method returns the BODY and HTML tags.
02:55 Now, save the file.
02:57 Before we try to run the script via the web server, let's try running it from the command line.
03:04 Switch back to the terminal and type: perl cgiexample.pl and press Enter.
03:12 The output looks like HTML.
03:15 Next, we will test the same script via the web server.
03:20 First, let us check whether web server is working or not.
03:25 Open your web browser and enter the IP address of the machine and press Enter.
03:31 Otherwise, you can type as "localhost".
03:35 If everything works fine, you will see something like this in the browser.
03:40 If you get any error, then the web service is not installed or it is not in ON status.
03:48 Apache HTTP server is installed in my machine.
03:52 If it is not installed, execute the below command on the terminal.
03:58 Otherwise, please ask your system administrator for server configuration.
04:04 Now, we will test the same script via the web server.
04:09 For this, we need to follow certain steps.
04:13 First place our program in the cgi-bin directory where the web server will recognize it as a CGI script.
04:22 The program filename must end with dot pl or dot cgi extension.
04:29 Set permission for the file to execute on the server.
04:33 Run the script.
04:35 The URL for this program will be as shown in the slide.
04:40 Switch to the terminal.
04:42 Now, we will copy the file to the cgi-bin directory.
04:47 For this, type the command:

sudo space cp space cgiexample.pl /usr/lib/cgi-bin/.

05:03 Enter the password if required.
05:06 Next, we need to give the Web-server user 'read' and 'execute' permission for the file.
05:13 For this, type: sudo space chmod space 755 space /usr/lib/cgi-bin/cgiexample.pl
05:31 Now our file which is placed in the cgi-bin directory is ready to execute.
05:38 Go to the web browser.
05:41 Type: localhost/cgi-bin/cgiexample.pl and press Enter.
05:50 We can see the output that is executed on the web browser.
05:55 Now, let us see another program. This program will add fields to a form and retrieve the entered values to our web page.
06:06 In the cgi-bin directory created earlier, I have saved a file form.cgi. I will open this file in gedit.
06:17 Now, add the below lines. This program generates a feedback form.
06:24 The user has to enter the first name, last name, gender and feedback details.
06:31 To begin a form, we are using start_form() method.
06:36 Form field methods are very similar to the standard html tag methods.
06:42 To create a textbox in the form, Textfield method is used with several parameters.
06:49 Here “fname”, “lname” are the names of the textbox which get the input from the user.
06:57 radio underscore group specifies the radio button with two options “Male” and “Female”.
07:05 This is denoted by the parameter hyphen values.
07:09 hyphen default parameter indicates the default selection of the radio button.
07:15 popup underscore menu specifies the listbox option.
07:20 Submit button is used to submit the entered data to the URL provider.
07:26 Clear button is used to clear the form.
07:30 The displayform function retrieves the values, we entered in the form.
07:36 param() function gives the value of the form field whose name is passed as parameter.
07:42 Here “fname” is the name given to the “First Name” textbox.
07:47 The value is retrieved and stored in the variable dollar name1.
07:53 Let us execute the program now.
07:56 Go to the web browser.
07:58 Type: localhost/cgi-bin/form.cgi and press Enter.
08:06 The feedback form is displayed.
08:09 I'll enter data in this form as shown here.
08:15 Then, press the Submit button to see the output that is retrieved from the form.
08:21 This brings us to the end of this tutorial. Let us summarize.
08:26 In this tutorial, we learnt how to create html pages using CGI module.
08:33 Assignment-

In form.cgi program, add checkbox option for languages Java, C/C++ and Perl.

08:44 Add textarea option to get the user feedback.
08:48 Print the user entered information on the webpage.
08:52 The video at the following link summarises the Spoken Tutorial project.

Please download and watch it.

08:59 The Spoken Tutorial Project Team:
  • conducts workshops using spoken tutorials and
  • gives certificates on passing online tests.
09:08 For more details, please write to us.
09:11 Spoken Tutorial project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at this link.

09:23 This is Nirmala Venkat from IIT Bombay, signing off. Thanks for watching.

Contributors and Content Editors

PoojaMoolya, Sandhya.np14