Perl Code Snippets

Sometimes it may be necessary to accept input from the user so that it can be utilised within a script. This can be achieved using 'STDIN'. Here, the input is placed into a variable called 'user' and then displayed as part of a greeting.

use strict;
use warnings;

# Greeting variable.
my $greeting = "Hello";

# Accept user input.
print "Please enter your name: ";
my $user = ;

# Display greeting.
print "$greeting $user";

When dealing with directories and files it may be necessary to check for their existence. Below is an example of how to do this.

use strict;
use warnings;

# Example path and file.
my $examplePath = "C:\\demo\\";
my $exampleFile = "C:\\demo\\example.txt";

# Check if the path exists.
if (-d $examplePath)
{
    print "The path '$examplePath' exists.\n"
}
else
{
    print "The path '$examplePath' doesn't exist.\n"
}

# Check if the file exists.
if (-e $exampleFile)
{
    print "The file '$exampleFile' exists.\n" 
}
else
{
    print "The file '$exampleFile' doesn't exist.\n"
}

This works in the same way on Unix like operating systems, such as Linux.

use strict;
use warnings;

# Example path and file.
my $examplePath = "/home/demouser/demo";
my $exampleFile = "/home/demouser/demo/example.txt";

# Check if the path exists.
if (-d $examplePath)
{
    print "The path '$examplePath' exists.\n"
}
else
{
    print "The path '$examplePath' doesn't exist.\n"
}

# Check if the file exists.
if (-e $exampleFile)
{
    print "The file '$exampleFile' exists.\n"
}
else
{
    print "The file '$exampleFile' doesn't exist.\n"
}

Perl can be used to copy and move files.

use strict;
use warnings;

use File::Copy;

# Example paths and files.
my $exampletPathSource = "C:\\demo\\";
my $exampletPathDestination = "C:\\demo\\backup";
my $exampleFile1 = "C:\\demo\\example1.txt";
my $exampleFile2 = "C:\\demo\\example2.txt";

# Copy the example1.txt file.
copy($exampleFile1, $exampletPathDestination) or die "Copy failed: $!";

# Move the example2.txt file.
move($exampleFile2, $exampletPathDestination) or die "Move failed: $!";

This works in the same way on Unix like operating systems, such as Linux.

use strict;
use warnings;

use File::Copy;

# Example paths and files.
my $exampletPathSource = "/home/demouser/demo";
my $exampletPathDestination = "/home/demouser/demo/backup";
my $exampleFile1 = "/home/demouser/demo/example1.txt";
my $exampleFile2 = "/home/demouser/demo/example2.txt";

# Copy the example1.txt file.
copy($exampleFile1, $exampletPathDestination) or die "Copy failed: $!";

# Move the example2.txt file.
move($exampleFile2, $exampletPathDestination) or die "Move failed: $!";

Here is an example of how to generate a random number between two values, in this case 1 and 59, then display it.

use strict;
use warnings;

# Generate random number.
my $random_number = int(rand(59)) + 1;

# Display the result.
print "Random number between 1 and 59: $random_number\n";

Here, a random 20 character password is generated from a specified set of characters.

use strict;
use warnings;

# Possible characters in password.
my @allowedChars = ('a'..'z', 'A'..'Z', 0..9,'!','_','-','$','@','!');

# Create a random 20 character password.
my $randPassword = join '', map $allowedChars[rand @allowedChars], 0..20;

# Display the generated password.
print "$randPassword"

A text file can be read from and processed line by line.

use strict;
use warnings;

# Text file to read.
my $filename = "C:\\demo\\example.txt";

# Open the text file using a file handler.
open(FH, '<', $filename) or die $!;

# Read the text file using a file handler.
while (<FH>)
{
    # Display the line of text.
    print $_;
}

# Close the file handler.
close(FH);