Perl Quick References

Posting my personal Perl quick reference.

Perl Quick Start Template

When starting a new script, you can use this template as a base which consists of:

1. RCS, CVS or SVN "Id" keyword to keep the version information.
2. Support script arguments.
3. Show usage function.
4. A trim function.

#!/usr/bin/perl -w
# $Id: $
#
use strict;
use Getopt::Long;

my $VERSION = "1.0";

my %option;
die unless GetOptions(
    "help"         => \$option{'help'},
);

if (defined( $option{'help'} )) {
    print_usage();
}

...


# Perl trim function to remove whitespace from the start and end of the string
sub trim {
    my $string = shift;
    $string =~ s/^\s+//;
    $string =~ s/\s+$//;
    return $string;
}

# Print usage
sub print_usage {
    my $usage = <<EOF;
DESCRIPTION:
    

OPTIONS:
    --[h]elp    Show this help text.

EXAMPLE:
    \$ $0
EOF
    die($usage);
}

How to Change Linux Password via SSH

Script to change Linux password remotely via SSH.

Prerequisite
For ActivePerl users, you need to download the Net::SSH2 package. Version 5.10.x

C:\>ppm install http://cpan.uwinnipeg.ca/PPMPackages/10xx/Net-SSH2.ppd

Version 5.12.x

C:\>ppm install http://cpan.uwinnipeg.ca/PPMPackages/12xx/Net-SSH2.ppd

Scripts

#!/usr/bin/perl 

use strict;
use Net::SSH2;

use Getopt::Long;

my %option = (
    'server'       => 'localhost',
    'userid'       => '',
    'password'     => '',
    'newpassword'  => '',
);

if (!GetOptions("server|s=s"       => \$option{'server'},
                "userid|u=s"       => \$option{'userid'}, 
                "password|p=s"     => \$option{'password'}, 
                "newpassword|n=s"  => \$option{'newpassword'})) {
    print_usage();  
}

my $ssh2 = Net::SSH2->new();

$ssh2->connect($option{'server'}) or die "Unable to connect Host $option{'server'} \n";

$ssh2->auth_password($option{'userid'}, $option{'password'}) or die "Unable to login\n";

my $chan = $ssh2->channel();
$chan->blocking(0);
$chan->ext_data('merge');

my $cmd = "chage -l $option{'userid'}; " 
        . "echo -e \"$option{'password'}\\n$option{'newpassword'}\\n$option{'newpassword'}\\n\" | passwd 2>&1\n";

# print $cmd;

$chan->exec($cmd);

while (<$chan>) { 
    print $_;
} 

#########################################################################
# Subroutines
#########################################################################
sub print_usage {
    # ...
}

Check for Holiday with Perl

In some cases we would like to avoid to execute the script during public holiday e.g. Don’t send alert during holiday. This script contains 2 functions i.e. “load_holiday_file” and “is_holiday” where you can include in your script to check for holiday.

#!/usr/bin/perl
use strict;

my @holidays = ();
my @now = localtime(time());

my $date = sprintf("%02d-%02d-%04d", $now[3], $now[4]+1, $now[5]+1900 );

load_holiday_file(\@holidays, 'holiday.txt');

if (is_holiday(\@holidays, $date)) {
    print "Today is holiday";
}

# Check the date is holiday
# "date_to_check" is in "DD-MM-YYYY" format.
sub is_holiday {
    my $holidays = shift;
    my $date_to_check = shift;
       
    my $counter = 0;
    my $found = 0;
       
    while($counter <= $#{holidays} && !$found) {
        my $holiday = $holidays->[$counter];
               
        if ($date_to_check =~ /^$holiday/) {
            $found = 1;
        }
        else {           
            $counter++;
        }   
    }

    return $found;
}

# Load holiday file
# Holiday file
# 1. DD-MM-YYYY
# 2. DD-MM (Every year on this date)
sub load_holiday_file {
    my $holidays     = shift;
    my $holiday_file = shift;
       
    if (open(HOLIDAY_FILE, $holiday_file)) {
   
        my $line;
        while (defined($line = <HOLIDAY_FILE>)) {   
            chomp($line);
             
            next if ($line =~ /^\s*#/ );
            next if ($line =~ /^$/);
           
            # Trim the string
            $line =~ s/^\s+//;   
            $line =~ s/\s+$//;
                                               
            push @{holidays}, $line;
        }        
        close(HOLIDAY_FILE);
    }
} 












Holiday File
# Holiday file
# 1. DD-MM-YYYY
# 2. DD-MM (Every year on this date)
27-01-2011       
03-02-2011
03-02-2011
22-04-2011
02-05-2011
17-05-2011
09-08-2011
30-08-2011
26-10-2011
06-11-2011
26-12-2011
02-01-2012