November 2012 | Linux Blog

Perl Script - Manipulating Arrays of Arrays (Multidimensional Arrays)

Below is simple Perl scrip which demonstrate the usage of multi-dimension arrays (array of arrays)

Feel free to copy and use this code ..

Source: cat multi-dimensional_array.pl
#!/usr/bin/perl

# Multi-dimension array by reference.
$array = ["A", "B", ["1", "2", "3", ["x", "y", "z"]]];

print "\$array->[0] == $array->[0] \n";
print "\$array->[1] == $array->[1] \n";

print "\$array->[2][1] == $array->[2][1] \n";
print "\$array->[2][2] == $array->[2][2] \n";

print "\$array->[2][3][0] == $array->[2][3][0] \n";
print "\$array->[2][3][1] == $array->[2][3][1] \n";
print "\$array->[2][3][2] == $array->[2][3][2] \n";

print " --------------------------------------- \n" ;

@array1 = (
"A", "B",
["1", "2", "3", ["x", "y", "z"]]
);

Perl Script: Creating pointers (References) to variable, Array and Hash

A reference is a scalar value that points to a memory location that holds some type of data. Everything in your Perl program is stored inside your computer's memory. Therefore, all of your variables, array, hash and functions are located at some memory location. References are used to hold the memory addresses.

Below is simple Perl script which demonstrate the usage of reference ...

Source: cat pointer.pl
#!/usr/bin/perl

# Creating pointer to a variable.
$var = 10;
$pointer = \$var;
print "Pointer address is: $pointer \n";
print "value store at $pointer is $$pointer \n";

print "--------------------------------\n";

# Creating pointer to an array.
@array = ("1", "2", "3", "4");
$array_pointer = \@array;
print "Address of the array in the memory: $array_pointer \n";

$len = scalar(@$array_pointer);
print "Length of the array: $len \n";

for ($i=0; $i<$len; $i++) {
print "$$array_pointer[$i] \n";
}

Perl Script: Signal Handling

You can control how your program responds to signals it receives. To do this, modify the %SIG associative array. This array contains one element for each available signal, with the signal name serving as the subscript for the element.

Below is simple Perl script which demonstrate the way to handle the interrupt signal...

Source: cat signal.pl
#!/usr/bin/perl

$SIG{"INT"} = "catch_signal";
while (1){
        print "waiting for signal ... press ctl+c to catch the interrupt signal \n";
        sleep(1);
}

sub catch_signal {
        print "\n Kool, I am able to handle interrupt signal \n";
        exit();
}

Output: perl signal.pl
waiting for signal ... press ctl+c to catch the interrupt signal
waiting for signal ... press ctl+c to catch the interrupt signal
waiting for signal ... press ctl+c to catch the interrupt signal
waiting for signal ... press ctl+c to catch the interrupt signal
waiting for signal ... press ctl+c to catch the interrupt signal
^C
Kool, I am able to handle interrupt signal

Perl Script: Read the Environment Variables

The %ENV associative array lists the environment variables defined for a program and their values. The environment variables are the array subscripts, and the values of the variables are the values of the array elements.

Source: cat env_variable.pl
#!/usr/bin/perl

$term = $ENV{"TERM"};
print "Terminal you are using: $term \n";

$desktop = $ENV{"DESKTOP_SESSION"};
print "Desktop you are using: $desktop \n";

$lang = $ENV{"LANGUAGE"};
print "Lang you are using: $lang \n";

Output: perl env_variable.pl
Terminal you are using: xterm
Desktop you are using: kde-plasma
Lang you are using: en_US:

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Perl Script: Input Line/record Separator examples

The input line/record separator ($/) is set to newline by default. Works like awk's RS variable, including treating blank lines as delimiters if set to the null string. You may set it to a multi-character string to match a multi-character delimiter, or can be set to the numeric value.

Below is simple perl script which demonstrate the usage of input record separator, feel free to copy and use this script.

Input File: cat testfile.txt
google:yahoo:microsoft:apple:oracle:hp:dell:toshiba:sun:redhat

Source: cat separator.pl
#!/usr/bin/perl

$FILE = "testfile.txt";
open (INFILE, $FILE) or die ("Not able to open the file");
$/ = ":";
while ($record = <INFILE>) {
print "$record \n";
}

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