Found 470 Articles for Programming Scripts

The kill() Function in Perl

Mohd Mohtashim
Updated on 02-Dec-2019 10:51:53

612 Views

Perl kill('KILL', (Process List)) function can be used to terminate a pseudo-process by passing it the ID returned by fork().Note that using kill('KILL', (Process List)) on a pseudo-process() may typically cause memory leaks, because the thread that implements the pseudo-process does not get a chance to clean up its resources.You can use kill() function to send any other signal to target processes, for example following will send SIGINT to a process IDs 104 and 102 −#!/usr/bin/perl kill('INT', 104, 102); 1;

The fork() Function in Perl

Mohd Mohtashim
Updated on 02-Dec-2019 10:49:35

3K+ Views

Perl provides a fork() function that corresponds to the Unix system call of the same name. On most Unix-like platforms where the fork() system call is available, Perl's fork() simply calls it. On some platforms such as Windows where the fork() system call is not available, Perl can be built to emulate fork() at the interpreter level.The fork() function is used to clone a current process. This call create a new process running the same program at the same point. It returns the child pid to the parent process, 0 to the child process, or under if the fork is ... Read More

The system() Function in Perl

Mohd Mohtashim
Updated on 02-Dec-2019 10:44:06

9K+ Views

You can use system() Perl function to execute any Unix command, whose output will go to the output of the perl script. By default, it is the screen, i.e., STDOUT, but you can redirect it to any file by using redirection operator > −#!/usr/bin/perl system( "ls -l") 1;When 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 15:16 index.htm drwxr-xr-x 3 544 401 4096 Jul 6 16:49 MIME-Lite-3.01 ... Read More

Backstick Operator in Perl

Mohd Mohtashim
Updated on 02-Dec-2019 10:38:35

152 Views

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 More

What are Perl Modules?

Mohd Mohtashim
Updated on 02-Dec-2019 10:37:10

127 Views

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 More

BEGIN and END Blocks in Perl

Mohd Mohtashim
Updated on 02-Dec-2019 10:32:20

1K+ Views

You may define any number of code blocks named BEGIN and END in Perl programs, which act as constructors and destructors respectively.BEGIN { ... } END { ... } BEGIN { ... } END { ... }Every BEGIN block is executed after the perl script is loaded and compiled but before any other statement is executed.Every END block is executed just before the perl interpreter exits.The BEGIN and END blocks are particularly useful when creating Perl modules.Following example shows its usage −Example Live Demo#!/usr/bin/perl package Foo; print "Begin and Block Demo"; BEGIN {    print "This is BEGIN Block" } END { ... Read More

What are Packages in Perl?

Mohd Mohtashim
Updated on 02-Dec-2019 10:30:06

148 Views

The package statement in Perl switches the current naming context to a specified namespace (symbol table). Thus −A package is a collection of code which lives in its own namespace.A namespace is a named collection of unique variable names (also called a symbol table).Namespaces prevent variable name collisions between packages.Packages enable the construction of modules which, when used, won't clobber variables and functions outside of the modules's own namespace.The package stays in effect until either another package statement is invoked, or until the end of the current block or file.You can explicitly refer to variables within a package using the :: package ... Read More

How to use Cookies in CGI in Perl?

Mohd Mohtashim
Updated on 02-Dec-2019 08:14:12

1K+ Views

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 More

Using POST Methods in Perl

Mohd Mohtashim
Updated on 02-Dec-2019 08:11:48

1K+ Views

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 More

Using GET Methods in Perl

Mohd Mohtashim
Updated on 02-Dec-2019 08:09:56

431 Views

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 More

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