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Programming Scripts Articles
Page 27 of 33
Backstick Operator in Perl
This simplest way of executing any Unix command in Perl Program is by using backstick operator. You simply put your command inside the backstick operator, which will result in execution of the command and returns its result which can be stored as follows −#!/usr/bin/perl @files = `ls -l`; foreach $file (@files) { print $file; } 1;When the above code is executed, it lists down all the files and directories available in the current directory −drwxr-xr-x 3 root root 4096 Sep 14 06:46 9-14 drwxr-xr-x 4 root root 4096 Sep 13 07:54 android -rw-r--r-- 1 root root 574 Sep 17 ...
Read MoreWhat are Perl Modules?
A Perl module is a reusable package defined in a library file whose name is the same as the name of the package with a .pm as extension.A Perl module file called Foo.pm might contain statements like this.#!/usr/bin/perl package Foo; sub bar { print "Hello $_[0]" } sub blat { print "World $_[0]" } 1;Few important points about Perl modulesThe functions require and use will load a module.Both use the list of search paths in @INC to find the module.Both functions require and use call the eval function to process the code.The 1; at the bottom causes eval to evaluate to TRUE (and thus not ...
Read MoreHow to use Cookies in CGI in Perl?
HTTP protocol is a stateless protocol. But for a commercial website it is required to maintain session information among different pages. For example one user registration ends after transactions which spans through many pages. But how to maintain user's session information across all the web pages?In many situations, using cookies is the most efficient method of remembering and tracking preferences, purchases, commissions, and other information required for better visitor experience or site statistics.How It WorksYour server sends some data to the visitor's browser in the form of a cookie. The browser may accept the cookie. If it does, it is ...
Read MoreUsing POST Methods in Perl
A more reliable method of passing information to a CGI program is the POST method. This packages the information in exactly the same way as GET methods, but instead of sending it as a text string after a ? in the URL, it sends it as a separate message as a part of HTTP header. Web server provides this message to the CGI script in the form of the standard input.Below is the Perl script called hello_post.cgi, to handle input given by the web browser. This script will handle GET as well as POST method.#!/usr/bin/perl local ($buffer, @pairs, $pair, $name, $value, %FORM); # ...
Read MoreUsing GET Methods in Perl
Here is a simple URL which will pass two values to hello_get.cgi program using GET method.http://www.tutorialspoint.com/cgi-bin/hello_get.cgi?first_name=ZARA&last_name=ALIBelow is hello_get.cgi script to handle input given by web browser.#!/usr/bin/perl local ($buffer, @pairs, $pair, $name, $value, %FORM); # Read in text $ENV{'REQUEST_METHOD'} =~ tr/a-z/A-Z/; if ($ENV{'REQUEST_METHOD'} eq "GET") { $buffer = $ENV{'QUERY_STRING'}; } # Split information into name/value pairs @pairs = split(/&/, $buffer); foreach $pair (@pairs) { ($name, $value) = split(/=/, $pair); $value =~ tr/+/ /; $value =~ s/%(..)/pack("C", hex($1))/eg; $FORM{$name} = $value; } $first_name = $FORM{first_name}; $last_name = $FORM{last_name}; print "Content-type:text/html\r\r"; print ""; print ""; print "Hello - Second CGI ...
Read MoreRaise a "File Download" Dialog Box using Perl
Sometime it is desired that you want to give option where a user will click a link and it will pop up a "File Download" dialogue box to the user instead of displaying actual content. This is very easy and will be achieved through HTTP header using Perl Script.This HTTP header will be different from the header mentioned in previous section. For example, if you want to make a FileName file downloadable from a given link then it's syntax will be as follows −#!/usr/bin/perl # HTTP Header print "Content-Type:application/octet-stream; name = "FileName"\r"; print "Content-Disposition: attachment; filename = "FileName"\r"; # Actual ...
Read MorePerl CGI Environment Variables
All the Perl CGI program will have access to the following environment variables. These variables play an important role while writing any CGI program in Perl.Sr.NoVariables Names & Description1CONTENT_TYPEThe data type of the content. Used when the client is sending attached content to the server. For example file upload, etc.2CONTENT_LENGTHThe length of the query information. It's available only for POST requests3HTTP_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. Its name of the web browser.5PATH_INFOThe path for the CGI script.6QUERY_STRINGThe URL-encoded information that is sent ...
Read MoreFirst CGI Program using Perl
Here is a simple Perl CGI program available in file called hello.cgi. This file has been kept in /cgi-bin/ directory and it has the following content. Before running your CGI program, make sure you have change mode of file using chmod 755 hello.cgi UNIX command.#!/usr/bin/perl print "Content-type:text/html\r\r"; print ''; print ''; print 'Hello Word - First CGI Program'; print ''; print ''; print 'Hello Word! This is my first CGI program'; print ''; print ''; 1;Now if you click hello.cgi link then request goes to web server who search for hello.cgi in /cgi-bin directory, execute it and whatever result got generated, web server sends that result ...
Read MoreUseful DBI Functions in Perl
Checking available_drivers@ary = DBI->available_drivers; @ary = DBI->available_drivers($quiet);Returns a list of all available drivers by searching for DBD::* modules through the directories in @INC. By default, a warning is given if some drivers are hidden by others of the same name in earlier directories. Passing a true value for $quiet will inhibit the warning.Checking installed_drivers%drivers = DBI->installed_drivers();Returns a list of driver name and driver handle pairs for all drivers 'installed' (loaded) into the current process. The driver name does not include the 'DBD::' prefix.Checking data_sources@ary = DBI->data_sources($driver);Returns a list of data sources (databases) available via the named driver. If $driver is ...
Read MoreUsing NULL Values in Perl Database Operation
Undefined values, or undef, are used to indicate NULL values in Perl’s Database Operations. You can insert and update columns with a NULL value as you would a non-NULL value. These examples insert and update the column age with a NULL value −$sth = $dbh->prepare(qq { INSERT INTO TEST_TABLE (FIRST_NAME, AGE) VALUES (?, ?) }); $sth->execute("Joe", undef);Here qq{} is used to return a quoted string to prepare API. However, care must be taken when trying to use NULL values in a WHERE clause. Consider −SELECT FIRST_NAME FROM TEST_TABLE WHERE age = ?Binding an undef (NULL) to the placeholder will ...
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