Arrays in Perl

 This blog talks about below topics related to Arrays:

1. Defining an array
2. Printing an array
3. Defining big array
4. Getting Length of an array
5. Adding and Removing elements in an array
6. Slicing array elements
7. Replacing Array element (splice)
8. String to array
9. Array to String
10. Sorting an array
11. Searching a element in an array
12. Comparing 2 arrays

NOTE: Each element of the array can be indexed using a scalar version of the same array. When an array is defined, PERL automatically numbers each element in the array beginning with zero. This phenomenon is termed array indexing.

Define an array

# Define an array
@names = ("Rinkesh","Bansal","Rinku");
 
# Define an array alternate way
@names = qw(Rinkesh Bansal Rinku);

Print an array

# Print array
# 1. Displays all members separated by space
print "@names";
# Output: Rinkesh Bansal Rinku

# 2. Displays all members without any separator
print @names;
# Output: RinkeshBansalRinku


# 3. Display each array element properly
foreach my $name (@names)
{
    print "$name\n";
}
# Output:
Rinkesh
Bansal
Rinku


# 4. Display each array element properly. This is array indexing
print "$name[0]\n";
print "$name[1]\n";
print "$name[2]\n";
# Output:
Rinkesh
Bansal
Rinku

# 5. Display each array element properly. This is array indexing using negative integers

print "$name[0]\n";
print "$name[-1]\n";
print "$name[-2]\n";

# Output:
Rinkesh

Rinku
Bansal
 

Define big array

# Define array with multiple values to save time

@10 = (1 .. 10);
@100 = (1 .. 100);
@1000 = (100 .. 1000);
@abc = (a .. z);


print "@10\n";


print "@100\n";

print "@1000\n";

print "@abc\n";

# Output: it will print 1 to 10 in first line, 1 to 100 in next, 100 to 1000 in next and a to z in last line

Getting length of an array

#  Finding the length of an Array
print scalar(@10),"\n";

print scalar(@100),"\n";
print scalar(@1000),"\n";
print scalar(@abc),"\n";
# Output:
10
100
901
26

Adding and Removing Elements

# Below functions were available to add/remove elements

• push(@array, Element): adds an element to the end of an array
• unshift(@array, Element): adds an element to the beginning of an array
• pop(@array): removes the last element of an array
• shift(@array): removes the first element of an array
• delete $array[index]: Removes an element by index number

 add_remove.pl

# Define an array
@count = ("one","two","three");

# Add Elements
push(@count, "four");
print "@count\n";
unshift(@count, "five");
print "@count\n";

# Remove Elements
pop(@count);
print "@count\n";
shift(@count);

# BACK TO HOW IT WAS
print "@count\n";

# Output:
one two three four
five one two three four
five one two three
one two three

Slicing Array Elements

slice1.pl

@count = ("one","two","three");
@sliceCount = @count[0,2];
print "@sliceCount\n";

# Output: one three

slice2.pl

@100 = (1..100);
@slice100 = @100[10..20,50..60,90..100];
print "@slice100";

# Output:
11 12 13 14 15 16 17 18 19 20 21 51 52 53 54 55 56 57 58 59 60 61 91 92 93 94 95 96 97 98 99 100

Replacing Array Elements (Splice)

Usage: splice(@array,first-element,sequential_length,name of new elements)

splice1.pl

@nums = (1..20);
splice(@nums, 5,5,21..25);
print "@nums\n";

# Output: 1 2 3 4 5 21 22 23 24 25 11 12 13 14 15 16 17 18 19 20

# Explanation: Actual replacement begins after the 5th element, starting with the number 6 in the example above. Five elements are then replaced from 6-10 with the numbers 21-25.

String to Array (split)

Usage: split(delimiter, String)

delimiter is the character using which string will be splitted

split1.pl

$string = "Welcome-to-Hell";
$name = "Rinkesh,Rinku,Bansal";

@array = split('-',$string);
@names = split(',',$name);

print "@array\n";
print "@names\n";

# Output: 

Welcome to Hell
Rinkesh Rinku Bansal

Array to String (join)

Usage: join(delimiter, Array)

delimiter is the character using which join will happen

join1.pl

@names = ("Rinkesh","Rinku","Bansal");
@array = qw(Welcome to Hell);

$name = join(",",@names);
$string = join(" ",@array);

print "$name\n";
print "$string\n";

# Output: 

Rinkesh,Rinku,Bansal 

Welcome to Hell

Sorting Arrays (sort)

Usage: sort(Array)

The sort() function sorts each element of an array according to ASCII Numeric standards. Please view ASCII-Table for a complete listing of every ASCII Numeric character.

sort1.pl

@first = qw(one two three four five);
@second = qw(one Two three Four five);

@first = sort(@first);
@second = sort(@second);

print "@first\n";
print "@second";

# Output: 

five four one three two
Four Two five one three
# Explanation: Capital letters have a lower ASCII Numeric value than lower letters.  Best option is to convert all array elements to lower characters and then sort to get accurate result

sort2.pl

@first = qw(one two three four five);
@second = qw(one Two three Four five);

@first = sort(@first);
foreach $temp (@second)
{
    push(@second_lc, lc($temp));
}
@second_lc = sort(@second_lc);

print "@first\n";
print "@second_lc";

# Output: 

five four one three two
five four one three two

Searching a element in an array

my $str = "three";
my @count = ("one","two","three");

if ($str ~~ @count)
{
    print "\n$str exists\n";
}
else
{
    print "\n$str doesn't exists\n";
}

# Output:
three exists

Comparing 2 arrays

my @first = qw(one three two four five);
my @second = qw(one two three four five);

if (@first ~~ @second)
{
    print "array matches\n";
}
else
{
    print "\nArray doesn't match\n";
}

@first = sort(@first);
@second = sort(@second);

if (@first ~~ @second)
{
    print "array matches\n";
}
else
{
    print "\nArray doesn't match\n";
}

#Output:

Array doesn't match

array matches

Setting Environment variable

# Function Name    : setEnv
# Input            : key and value
# Output        : none
# Description    : This funtion will set environment variable for current and child process
# Created By    : Rinkesh Bansal
#
sub setEnv($$)
{
    my ($key, $value) = @_;
    my $delimiter;
    my $os = $^O;
    if ($os eq "MSWin32")
    {
        $delimiter = ";";
    }
    else
    {
        $delimiter = ":";
    }

    $ENV{$key}=$ENV{$key} . $delimiter . $value;
}

Calculating md5dum of all files in a folder

# Function Name : md5sum_dir
# Input            : Path of folder
# Output        : none
# Description    : This function will recursively check md5sum of all files under passed folder
# Created By    : Rinkesh Bansal
#
sub md5sum_dir ($)
{
    my $path = shift;

    opendir (DIR, $path) or die "Unable to open $path: $!";
    my @files = map {$path . '/' . $_ }grep { !/^\.{1,2}$/ } readdir (DIR);
    closedir (DIR);

    foreach my $file (@files)
    {
        if (-d $file)
        {
            &md5sum_dir ($file);
        }
        else
        {
            my $md = &md5sum($file); # you can find this subroutine in my other blogs
            open (FO, ">>$result_file") or die ("Error :: Couldn't open file ($result_file) for writing\n");
            print FO "$file\t$md\n";
            close(FO);
        }
    }
}

Calculating md5sum of a given file

use Digest::MD5; # make sure to have this package added in your perl script

# Function Name : md5sum
# Input            : File for which md5sum is requested
# Output        : md5sum of the file
# Description    : This function will calculate the md5sum (checksum) of the file and return it.
# Created By    : Rinkesh Bansal
#
sub md5sum($)
{
    my $file = shift;
    die "Error::File ($file) does not exist!!!"    if (not -e $file);
    open (FO, $file);
    binmode(FO);
    my $md5 = Digest::MD5->new;
    while ()
    {
        $md5->add($_);
    }
    close(FO);
    my $checksum = $md5->hexdigest;
#    print "$checksum $file\n";
    return $checksum;
}

Clearing a screen

# Function Name    : clear_scr
# Input            : none
# Output        : none
# Description    : This funtion will clear the screen
# Created By    : Rinkesh Bansal
#
sub clear_scr()
{
    my $os = $^O;
    if ($os eq "MSWin32")
    {
        system 'cls';
    }
    else
    {
        system 'clear';
    }
}

copying a file

use File::Copy; # include this perl module in your program to make this function work

# Function Name : copyFile
# Input            : Source & Destination Location
# Output        : none
# Description    : This function will copy given source file to destination location.
# Created By    : Rinkesh Bansal
#
sub copyFile($$)
{
    my ($source, $target) = @_;
    if (-e $source)
    {
        my $targetdir;
        if (substr($target, -1) eq "/")
        {
            $targetdir = $target;
        }
        else
        {
            $targetdir = substr ($target, 0, rindex($target, "/"));
        }

        copy ($source, $target);
    }
}

logger functionality to create backup of files

# Function Name : backup_result_file
# Input            : Number of backups, Name of the result file
# Output        : none
# Description    : This function will create backup of result file. Max number of backups handle are passed as first parameter
# Created By    : Rinkesh Bansal
#
sub backup_result_file($$)
{
    my ($num_of_backup, $result_file) = @_;

    for (my $i = $num_of_backup - 2; $i > 0; $i--)
    {
        my $temp = $i + 1;
        my $source = "${result_file}.${i}";
        my $target = "${result_file}.${temp}";
        &copyFile($source, $target);
    }
    my $source = "${result_file}";
    my $target = "${result_file}.1";
    &copyFile($source, $target);
    unlink($source);
}