Perl CGI Hello World: Difference between revisions

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=[http://ojaperiwiva.co.cc This Page Is Currently Under Construction And Will Be Available Shortly, Please Visit Reserve Copy Page]=
<span id="top"></span>
&lt;span id=&quot;top&quot;&gt;&lt;/span&gt;
{| cellpadding="2"
{| cellpadding=&quot;2&quot;
|__TOC__||'''Perl CGI - Hello World'''
|__TOC__||'''Perl CGI - Hello World'''
|}
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{|
{|
|-
|-
!Shebang!!&amp;nbsp;||Notes
!Shebang!!&nbsp;||Notes
|-
|-
|valign=&quot;top&quot;|
|valign="top"|
&lt;pre&gt;#!/usr/bin/perl&lt;/pre&gt;
<pre>#!/usr/bin/perl</pre>
|
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&amp;nbsp;
&nbsp;
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It has the following format: Starts with a hash &quot;'''&lt;nowiki&gt;#&lt;/nowiki&gt;'''&quot; followed by an exclamation mark &quot;'''!'''&quot; and then the complete path on your system to the '''Perl''' program itself.
It has the following format: Starts with a hash "'''<nowiki>#</nowiki>'''" followed by an exclamation mark "'''!'''" and then the complete path on your system to the '''Perl''' program itself.


The shebang shown corresponds to Uniform Server running either in portable-mode (basic) or disk-root. The line informs Apache where to find the Perl program, &quot;'''/'''&quot; means start at the top level of a disk then follow the folder path '''usr''', '''bin''' and finally the name of the Perl program '''perl'''.exe note the file extension is assumed.
The shebang shown corresponds to Uniform Server running either in portable-mode (basic) or disk-root. The line informs Apache where to find the Perl program, "'''/'''" means start at the top level of a disk then follow the folder path '''usr''', '''bin''' and finally the name of the Perl program '''perl'''.exe note the file extension is assumed.
|-
|-
|valign=&quot;top&quot;|
|valign="top"|
&lt;pre&gt;#!c:/UniServer/usr/bin/perl&lt;/pre&gt;
<pre>#!c:/UniServer/usr/bin/perl</pre>
|
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&amp;nbsp;
&nbsp;
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When Uniform Server is installed as a service all Perl shebangs are changed to match the installation path. An example of this shebang is shown for a default installation of Mona installed as a service. Hence when writing new scripts remember to use the correct path for the shebang.  
When Uniform Server is installed as a service all Perl shebangs are changed to match the installation path. An example of this shebang is shown for a default installation of Mona installed as a service. Hence when writing new scripts remember to use the correct path for the shebang.  
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'''''Note 1'':''' The shebang can take parameters the most useful is '''-w''' it enables warnings remove it on finished scripts.
'''''Note 1'':''' The shebang can take parameters the most useful is '''-w''' it enables warnings remove it on finished scripts.
* &lt;nowiki&gt;#!/usr/bin/perl -w&lt;/nowiki&gt;
* <nowiki>#!/usr/bin/perl -w</nowiki>
* &lt;nowiki&gt;#!c:/UniServer/usr/bin/perl -w&lt;/nowiki&gt;
* <nowiki>#!c:/UniServer/usr/bin/perl -w</nowiki>


'''''Note 2'':''' Forward slashes are Unix paths if you wish you can use a back slash the path must be enclosed in quotes.
'''''Note 2'':''' Forward slashes are Unix paths if you wish you can use a back slash the path must be enclosed in quotes.
* &lt;nowiki&gt;#!&quot;\usr\bin\perl&quot;&lt;/nowiki&gt;
* <nowiki>#!"\usr\bin\perl"</nowiki>
* &lt;nowiki&gt;#!&quot;c:\UniServer\usr\bin\perl&quot;&lt;/nowiki&gt;
* <nowiki>#!"c:\UniServer\usr\bin\perl"</nowiki>


'''''Note 3'':''' For maximum computability always use '''forward slashes''' and run Uniform Server in portable or disk-root mode.  
'''''Note 3'':''' For maximum computability always use '''forward slashes''' and run Uniform Server in portable or disk-root mode.  
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The first thing a CGI script must perform is to output a header. This header is checked by Apache and then passed on to a users browser informing it what type of file to expect. In the hello world examples we are outputting an HTML file hence the header looks like this:
The first thing a CGI script must perform is to output a header. This header is checked by Apache and then passed on to a users browser informing it what type of file to expect. In the hello world examples we are outputting an HTML file hence the header looks like this:
{|
{|
|valign=&quot;top&quot;|
|valign="top"|
&lt;pre&gt;print &quot;Content-type: text/html\n\n&quot;;&lt;/pre&gt;
<pre>print "Content-type: text/html\n\n";</pre>
|
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&amp;nbsp;
&nbsp;
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Its important to output it exactly as shown. Must start with a capital &quot;C&quot; followed by lowercase characters. Of importance are the two newline characters (\n\n) at the end of the header. The header needs to be followed by a blank line hence the second newline character.
Its important to output it exactly as shown. Must start with a capital "C" followed by lowercase characters. Of importance are the two newline characters (\n\n) at the end of the header. The header needs to be followed by a blank line hence the second newline character.
|-
|-
|valign=&quot;top&quot;|
|valign="top"|
&lt;pre&gt;print &quot;Content-type: text/html\r\n\r\n&quot;;&lt;/pre&gt;
<pre>print "Content-type: text/html\r\n\r\n";</pre>
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&amp;nbsp;
&nbsp;
|valign=&quot;top&quot;|
|valign="top"|
The above works fine on Windows.
The above works fine on Windows.


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|-
|-
|   
|   
&lt;pre&gt;
<pre>
#!/usr/bin/perl
#!/usr/bin/perl


# test_1.pl - First Perl Script!
# test_1.pl - First Perl Script!
print &quot;Content-type: text/html\r\n\r\n&quot;;
print "Content-type: text/html\r\n\r\n";
print &quot;Hello World\n&quot;; # Comment starts
print "Hello World\n"; # Comment starts
&lt;/pre&gt;
</pre>
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&amp;nbsp;
&nbsp;
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The first line is the shebang informing Apache where to find the Perl program.
The first line is the shebang informing Apache where to find the Perl program.


The second line starts with a hash &quot;#&quot; indicating the start of a comment, any character after this up to the end of a line are ignored. Although the shebang starts with a hash it is not a comment because it is combined with an exclamation mark the two together define a shebang. You can start a comment anywhere along a line, if a line is Perl code a comment must start after the line terminator character &quot;;&quot; semi-column.     
The second line starts with a hash "#" indicating the start of a comment, any character after this up to the end of a line are ignored. Although the shebang starts with a hash it is not a comment because it is combined with an exclamation mark the two together define a shebang. You can start a comment anywhere along a line, if a line is Perl code a comment must start after the line terminator character ";" semi-column.     
|}
|}
The third lines outputs (prints) the header.
The third lines outputs (prints) the header.
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* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Start the servers.
* Start the servers.
* Type the following into a browser: '''&lt;nowiki&gt;http://localhost/cgi-bin/test_1.pl&lt;/nowiki&gt;'''  
* Type the following into a browser: '''<nowiki>http://localhost/cgi-bin/test_1.pl</nowiki>'''  
'''''[[#top | Top]]'''''
'''''[[#top | Top]]'''''
== Script 2 - Basic HTML ==
== Script 2 - Basic HTML ==
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{|
{|
|-
|-
|valign=&quot;top&quot;|   
|valign="top"|   
&lt;pre&gt;
<pre>
#!/usr/bin/perl
#!/usr/bin/perl


# test_2.pl - Second Perl Script!
# test_2.pl - Second Perl Script!
print &quot;Content-type: text/html\r\n\r\n&quot;;
print "Content-type: text/html\r\n\r\n";


print &quot;&lt;HTML&gt;&quot;;
print "<HTML>";
print &quot;&lt;HEAD&gt;&quot;;
print "<HEAD>";
print &quot;&lt;TITLE&gt;Hello World&lt;/TITLE&gt;&quot;;
print "<TITLE>Hello World</TITLE>";
print &quot;&lt;/HEAD&gt;&quot;;
print "</HEAD>";
print &quot;&lt;BODY&gt;&quot;;
print "<BODY>";
print &quot;&lt;H1&gt;Hello World&lt;/H1&gt;&quot;;
print "<H1>Hello World</H1>";
print &quot;&lt;/BODY&gt;&quot;;
print "</BODY>";
print &quot;&lt;/HTML&gt;&quot;;
print "</HTML>";
&lt;/pre&gt;
</pre>
|
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&amp;nbsp;
&nbsp;
|valign=&quot;top&quot;|
|valign="top"|
The code is similar to the above includes a shebang, comment and header line.
The code is similar to the above includes a shebang, comment and header line.


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* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Start the servers.
* Start the servers.
* Type the following into a browser: '''&lt;nowiki&gt;http://localhost/cgi-bin/test_2.pl&lt;/nowiki&gt;'''  
* Type the following into a browser: '''<nowiki>http://localhost/cgi-bin/test_2.pl</nowiki>'''  


A page full of print statements becomes very tedious the next script makes the task a little easier.  
A page full of print statements becomes very tedious the next script makes the task a little easier.  
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{|
{|
|-
|-
|valign=&quot;top&quot;|   
|valign="top"|   
&lt;pre&gt;
<pre>
#!/usr/bin/perl
#!/usr/bin/perl


# test_3.pl - Third Perl Script!
# test_3.pl - Third Perl Script!
print &quot;Content-type: text/html\r\n\r\n&quot;;
print "Content-type: text/html\r\n\r\n";


print &lt;&lt;&quot;EOF123&quot;;
print <<"EOF123";
&lt;HTML&gt;
<HTML>
  &lt;HEAD&gt;
  <HEAD>
   &lt;TITLE&gt;Hello World&lt;/TITLE&gt;
   <TITLE>Hello World</TITLE>
  &lt;/HEAD&gt;
  </HEAD>
  &lt;BODY&gt;
  <BODY>
   &lt;H1&gt;Hello World&lt;/H1&gt;
   <H1>Hello World</H1>
  &lt;/BODY&gt;
  </BODY>
&lt;/HTML&gt;
</HTML>
EOF123
EOF123
&lt;/pre&gt;
</pre>
|
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&amp;nbsp;
&nbsp;
|valign=&quot;top&quot;|
|valign="top"|
With the exception of the header all print statements have been replaced with two special markers.
With the exception of the header all print statements have been replaced with two special markers.


A block of text to be printed is enclosed between''' print &lt;&lt;&quot;EOF123&quot;;''' and '''EOF123''' start and end tags respectively.     
A block of text to be printed is enclosed between''' print <<"EOF123";''' and '''EOF123''' start and end tags respectively.     


'''''Note 1'':''' There's nothing special about the &quot;EOF123&quot; string use anything you like however it must be identical in both cases.
'''''Note 1'':''' There's nothing special about the "EOF123" string use anything you like however it must be identical in both cases.


'''''Note 2'':''' The end tag '''EOF123''' must be place on its own line and no spaces are allowed at either the beging or end of the statement.
'''''Note 2'':''' The end tag '''EOF123''' must be place on its own line and no spaces are allowed at either the beging or end of the statement.
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* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Start the servers.
* Start the servers.
* Type the following into a browser: '''&lt;nowiki&gt;http://localhost/cgi-bin/test_3.pl&lt;/nowiki&gt;'''  
* Type the following into a browser: '''<nowiki>http://localhost/cgi-bin/test_3.pl</nowiki>'''  
Using here-doc is a real time-saver.
Using here-doc is a real time-saver.
|}
|}
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== Script 4 - Basic HTML CGI.pm function-oriented ==
== Script 4 - Basic HTML CGI.pm function-oriented ==
CGI.pm has two faces either function-oriented or object-oriented. This example shows how to use the function interface. The command '''Use CGI''' takes a parameter this allows us to import a set of functions from the CGI module. This example imports the &quot;'''standard'''&quot; set of functions from this module.
CGI.pm has two faces either function-oriented or object-oriented. This example shows how to use the function interface. The command '''Use CGI''' takes a parameter this allows us to import a set of functions from the CGI module. This example imports the "'''standard'''" set of functions from this module.


{|
{|
|-
|-
|valign=&quot;top&quot;|   
|valign="top"|   
&lt;pre&gt;
<pre>
#!/usr/bin/perl
#!/usr/bin/perl


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       h1('Hello World'),        # level 1 header
       h1('Hello World'),        # level 1 header
       end_html;                  # end of HTML
       end_html;                  # end of HTML
&lt;/pre&gt;
</pre>
|
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&amp;nbsp;
&nbsp;
|valign=&quot;top&quot;|
|valign="top"|
&lt;br&gt;'''''Running the script'''''
<br>'''''Running the script'''''
* Create a text file and copy the script. Save the file with name '''test_4.pl'''
* Create a text file and copy the script. Save the file with name '''test_4.pl'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Start the servers.
* Start the servers.
* Type the following into a browser: '''&lt;nowiki&gt;http://localhost/cgi-bin/test_4.pl&lt;/nowiki&gt;'''  
* Type the following into a browser: '''<nowiki>http://localhost/cgi-bin/test_4.pl</nowiki>'''  
|}
|}
The above is intended to provide a working example in no way does it indicate the enormity and flexibility of this module.
The above is intended to provide a working example in no way does it indicate the enormity and flexibility of this module.
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{|
{|
|-
|-
|valign=&quot;top&quot;|   
|valign="top"|   
&lt;pre&gt;
<pre>
#!/usr/bin/perl
#!/usr/bin/perl


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use CGI;                            # load CGI functions
use CGI;                            # load CGI functions
$q = new CGI;                        # create new CGI object
$q = new CGI;                        # create new CGI object
print $q-&gt;header,                    # create HTTP header
print $q->header,                    # create HTTP header
       $q-&gt;start_html('Hello World'), # start of HTML
       $q->start_html('Hello World'), # start of HTML
       $q-&gt;h1('Hello World'),        # level 1 header
       $q->h1('Hello World'),        # level 1 header
       $q-&gt;end_html;                  # end of HTML
       $q->end_html;                  # end of HTML
&lt;/pre&gt;
</pre>
|
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&amp;nbsp;
&nbsp;
|valign=&quot;top&quot;|
|valign="top"|
&lt;br&gt;'''''Running the script'''''
<br>'''''Running the script'''''
* Create a text file and copy the script. Save the file with name '''test_5.pl'''
* Create a text file and copy the script. Save the file with name '''test_5.pl'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Start the servers.
* Start the servers.
* Type the following into a browser: '''&lt;nowiki&gt;http://localhost/cgi-bin/test_5.pl&lt;/nowiki&gt;'''  
* Type the following into a browser: '''<nowiki>http://localhost/cgi-bin/test_5.pl</nowiki>'''  
|}
|}
Again the objective is to provide a working example. The above gives you some idea of the modules capabilities take a look at Perl's doc for more information.
Again the objective is to provide a working example. The above gives you some idea of the modules capabilities take a look at Perl's doc for more information.
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When a form is submitted its easy to pick-up the query string and process it. There is no need to use a form the query string can be included with the URL. This example demostrates the principal.
When a form is submitted its easy to pick-up the query string and process it. There is no need to use a form the query string can be included with the URL. This example demostrates the principal.


URL: '''&lt;nowiki&gt;http://localhost/cgi-bin/test_6.pl?part1=Hello&amp;part2=World&lt;/nowiki&gt;'''
URL: '''<nowiki>http://localhost/cgi-bin/test_6.pl?part1=Hello&part2=World</nowiki>'''


{|
{|
|-
|-
|valign=&quot;top&quot;|   
|valign="top"|   
&lt;pre&gt;
<pre>
#!/usr/bin/perl
#!/usr/bin/perl


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print header,              # create HTTP header
print header,              # create HTTP header
   start_html('Hello Page'); # start of HTML
   start_html('Hello Page'); # start of HTML
   my $p1 = param(&quot;part1&quot;);  # get first parameter   
   my $p1 = param("part1");  # get first parameter   
   my $p2 = param(&quot;part2&quot;);  # get second parameter   
   my $p2 = param("part2");  # get second parameter   
print  h1($p1.&quot; &quot;.$p2);    # level 1 header
print  h1($p1." ".$p2);    # level 1 header
print  end_html;            # end of HTML
print  end_html;            # end of HTML
&lt;/pre&gt;
</pre>
|
|
&amp;nbsp;
&nbsp;
|valign=&quot;top&quot;|
|valign="top"|
&lt;br&gt;'''''Running the script'''''
<br>'''''Running the script'''''
* Create a text file and copy the script. Save the file with name '''test_6.pl'''
* Create a text file and copy the script. Save the file with name '''test_6.pl'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Start the servers.
* Start the servers.
* Type the following into a browser:&lt;br&gt; '''&lt;nowiki&gt;http://localhost/cgi-bin/test_6.pl?part1=Hello&amp;part2=World&lt;/nowiki&gt;'''  
* Type the following into a browser:<br> '''<nowiki>http://localhost/cgi-bin/test_6.pl?part1=Hello&part2=World</nowiki>'''  
|}
|}
The query string '''?part1=Hello&amp;part2=World''' contains two name/value pairs  '''part1=Hello''' and '''part2=World'''. These values would normally be entered into a form using input tags and added to a URL when the page (form) is submitted.
The query string '''?part1=Hello&part2=World''' contains two name/value pairs  '''part1=Hello''' and '''part2=World'''. These values would normally be entered into a form using input tags and added to a URL when the page (form) is submitted.


The script picks-up our two values using CGI function '''param(&quot;input tag name&quot;)'''and assigns them to two variables '''$p1''' and '''£p2'''. The two variables (strings) are concatenated (joined together) and printed.
The script picks-up our two values using CGI function '''param("input tag name")'''and assigns them to two variables '''$p1''' and '''£p2'''. The two variables (strings) are concatenated (joined together) and printed.


'''''[[#top | Top]]'''''
'''''[[#top | Top]]'''''
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{|
{|
|-
|-
|valign=&quot;top&quot;|   
|valign="top"|   
&lt;pre&gt;
<pre>
#!/usr/bin/perl
#!/usr/bin/perl


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use CGI qw/:standard/;                                # load standard CGI routines
use CGI qw/:standard/;                                # load standard CGI routines
   my $p1 = param(&quot;part1&quot;);                            # get parameter   
   my $p1 = param("part1");                            # get parameter   
   my $p2 = param(&quot;part2&quot;);                            # get parameter   
   my $p2 = param("part2");                            # get parameter   
   my $p3 = param(&quot;part3&quot;);                            # get parameter   
   my $p3 = param("part3");                            # get parameter   
print header,                                          # create HTTP header
print header,                                          # create HTTP header
   start_html('Hello Page'),                            # start of HTML
   start_html('Hello Page'),                            # start of HTML
   h1('Simple form');                                  # level h1 header
   h1('Simple form');                                  # level h1 header
if ($p1 &amp;&amp; $p2 ){                                      # check both set  
if ($p1 && $p2 ){                                      # check both set  
   print p('Full name = '.$p1.&quot; &quot;.$p2);                # print variables
   print p('Full name = '.$p1." ".$p2);                # print variables
   print p('Extra info = '.$p3);                        # print variable
   print p('Extra info = '.$p3);                        # print variable
}
}
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print p('Enter First Name : ', textfield('part1','')); # add input tag
print p('Enter First Name : ', textfield('part1','')); # add input tag
print p('Enter Last Name  : ', textfield('part2','')); # add input tag
print p('Enter Last Name  : ', textfield('part2','')); # add input tag
print p('Extra:','&amp;nbsp;' x 18 ,popup_menu('part3',        # create dropdown menu
print p('Extra:','&nbsp;' x 18 ,popup_menu('part3',        # create dropdown menu
['Hello World 1','Hello World 2','Hello World 3']));  # menu values
['Hello World 1','Hello World 2','Hello World 3']));  # menu values
print p(submit('Send'));                              # add submit button
print p(submit('Send'));                              # add submit button
print end_form(),hr();                                # end form
print end_form(),hr();                                # end form
print  end_html;                                      # end of HTML
print  end_html;                                      # end of HTML
&lt;/pre&gt;
</pre>
|}
|}
'''''Running the script'''''
'''''Running the script'''''
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* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Copy this file to folder: '''UniServer\udrive\cgi-bin'''
* Start the servers.
* Start the servers.
* Type the following into a browser: '''&lt;nowiki&gt;http://localhost/cgi-bin/test_7.pl&lt;/nowiki&gt;'''  
* Type the following into a browser: '''<nowiki>http://localhost/cgi-bin/test_7.pl</nowiki>'''  


'''''[[#top | Top]]'''''
'''''[[#top | Top]]'''''
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For example to run '''test_1.pl''' copy it to folder '''www''' type the following into your browser:
For example to run '''test_1.pl''' copy it to folder '''www''' type the following into your browser:


'''&lt;nowiki&gt;http://localhost/test_1.pl&lt;/nowiki&gt;'''
'''<nowiki>http://localhost/test_1.pl</nowiki>'''


This is possible because cgi has been enabled in file '''.htaccess''' which is located in www. Open the file in a text editor you will find these two lines they have been un-commented (hash removed) hence enabled:
This is possible because cgi has been enabled in file '''.htaccess''' which is located in www. Open the file in a text editor you will find these two lines they have been un-commented (hash removed) hence enabled:


&lt;pre&gt;
<pre>
AddHandler cgi-script .pl .cgi
AddHandler cgi-script .pl .cgi
Options +ExecCGI
Options +ExecCGI
&lt;/pre&gt;
</pre>


The first line informs Apache files with the specified extension are to be processed as cgi scripts.
The first line informs Apache files with the specified extension are to be processed as cgi scripts.

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