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PERL Articles
Page 7 of 15
BEGIN and END Blocks in Perl
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#!/usr/bin/perl package Foo; print "Begin and Block Demo"; BEGIN { print "This is BEGIN Block" } END { ...
Read MoreThe fork() Function in Perl
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 MoreHow to count the number of keys in a Perl hash?
There are times when we would want to know how many key-value pairs are present in a hash. These key-value pair counts are also known as the size of the hash. In Perl, we can find the number of keys in a Perl hash by using the "scalar" keyword or "keys" keyword. In this tutorial, we will explore two Perl examples where we will calculate the number of keys in a hash. Example Consider the code shown below. In this code, we have declared a hash named "countries" and in that hash, we have different countries, each having ...
Read MoreHow to count the number of matches in a Perl string?
In Perl, we can find the number of matches in a string by different approaches. In this tutorial, we will discuss the three most widely used approaches. Searching for a Single Character in a Perl String Let's first take the case where we would want to search for a single character pattern in a string. For example, let's suppose we have a string that look something like this − "India.Japan.Russia.USA.China" And, we want to find the number of times "." (dot) appears in the above string. Example Consider the code shown below. my $countries ...
Read MoreHow to convert binary to decimal and vice versa in Perl?
The conversion between binary to decimal and decimal to binary is a necessity when it comes to dealing with binary data and using them in some simple applications. In Perl, we can convert from decimal to binary and vice versa in multiple ways. In this tutorial, we will explore different examples where we will first convert a decimal value into a binary value and then a binary value into a decimal value. Decimal to Binary in Perl Let's first see an example where we are given two decimal values and we want to convert them to their binary representation. ...
Read MoreHow to convert a string to a number in Perl?
In Perl, we can convert a string into a number by appending the integer value 0 in front of it. There are some other approaches too, which we will discuss in this tutorial with the help of examples. Example Let's first consider the case where the string that we are trying to convert looks something like "123abc" or "23Hzbc". You can see that the it is a mixture of both integer values and characters. Consider the code shown below. my $firstStr = '23ASDF'; print "Convering First String to Number: ", $firstStr + 0; print ""; my $secondStr = ...
Read MoreHow to compare two strings in Perl?
Perl has methods and operators that determine whether two string values are equal or different. In Perl, the compare strings function is essential for comparing two strings and their values. This check examines if two string values are equal or not by using the "eq" and "ne" operators. We can also compare two strings with the help of the "lt, gt, ge, le" operators as well. In this tutorial, we will consider all the approaches that can be used to compare two strings in Perl. The "eq" and "ne" Operators in Perl Let's start with the eq and ...
Read MoreHow to check if a file exists in Perl?
In this tutorial, we will take a couple of examples and demonstrate how you can if a file exists or not, with the help of Perl. Let's suppose we have a simple text file called "sample.txt" with the following data − This is a sample txt file that contains some content inside it. TutorialsPoint is simply amazing! We will use a Perl code to check whether this file exists or not. Example 1 The most basic approach to check whether a file exists or not is to use the "-e" flag and then pass the name of the file. ...
Read MoreHow to compare two arrays for equality in Perl?
In Perl, there are two ways to check if two arrays are equal. We can compare two arrays in Perl with the help of "Storable freeze" function or by creating our own custom function. In this tutorial, we will explore both these approaches with the help of examples. Example 1 Let's first explore the "Storable freeze" code and understand how it works. Consider the code shown below. use Storable qw/freeze/; use strict; $Storable::canonical = 1; my @countriesOne = ('India', 'China', 'Russia', 'USA', 'Germany'); my @countriesTwo = ('India', 'China', 'Russia', 'USA', 'Germany'); my @countriesThree = ...
Read MoreHow to check if a variable has a numeric value in Perl?
Suppose we get a variable at runtime in Perl and we want to check if the value that it contains is numeric or not, then we can use the two approaches shown in this tutorial. We will use two simple examples to demonstrate how it works. Example The most basic approach is to use the length and do keywords and then ignore the warnings. Consider the code shown below for the same. $x = 100; if (length(do { no warnings "numeric"; $x & "" })){ print "x is numeric"; } else { print ...
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