Discovering Coding !!!

How to interpolate hashes in double quotes under Perl

2011-08-29T18:16:00.000-07:00

Just like we can interpolate scalar variables and arrays in double quotes, why can't we interpolate hashes in Perl.

I always had this question until one day I decided to find the solution and understand the reason.

Reason: http://dev.perl.org/perl6/rfc/237.html

Solution (silly): https://github.com/paragkalra/my_scripts/blob/master/perl/hash_interpolation/hash_interpolation.pl

Add Custom Header to scripts using vim

2010-12-29T13:53:00.000-08:00

1. Create a template header: cat ~/.vim_header.pl

:insert
#
# $Id: $
#
# Copyright (c) 2011 Parag Kalra
# All rights reserved.
#
## @script
##
## @summary
##
## @description
##
## @usage
##
## @synopsis
##
## @param
##
## @keywords
##
## @status review
##
## @author
##
## @creation-date
##
## @last-modified
##
## @burts
##
## see-also
.

:insert should be present on first line and . should be present on last line

2. Add following lines to ~/.vimrc

autocmd bufnewfile *.pl so ~/.vim_header.pl
autocmd bufnewfile *.pl exe "1," . 30 . "g/@script.*/s//@script " .expand("%")
autocmd bufnewfile *.pl exe "1," . 30 . "g/@creation-date/s//@creation-date " .strftime("%d-%m-%Y")
autocmd Bufwritepre,filewritepre *.pl execute "normal ma"
autocmd Bufwritepre,filewritepre *.pl exe "1," . 30 . "g/last-modified/s/last-modified .*/last-modified " .strftime("%c")
autocmd bufwritepost,filewritepost *.pl execute "normal `a"

3. Now create a new file having .pl extension and see the magic.

Courtesy: http://www.thegeekstuff.com/2008/12/vi-and-vim-autocommand-3-steps-to-add-custom-header-to-your-file/

Locking Hashes - How to Lock Hashes in Perl

2010-12-14T01:04:00.000-08:00

One drawback of hashes is that their keys are barewords which offer little typo protection (especially compared to the function and variable name protection offered by the strict pragma). The core module Hash::Util provides mechanisms to restrict the modification of a hash or the keys allowed in the hash.

For examples have a look at my sample scripts here.

How to find if a Perl module is installed on the System

2010-12-13T23:23:00.000-08:00

Quick and Dirty way to find if a Perl module is installed on the System:

perl -MModule_Name -e 1

How to break from if - else in Perl

2010-01-18T11:33:00.000-08:00

One of the ways to break from if - else in Perl is to use goto

if ($num =~ /^\d+$/){
if($num == 13){
goto ENDOFIF;
}
} else {
print "Number not found.\n";
ENDOFIF:
}

So if the number is 13 then it will break from the if and place the control right at the end of outer if.

How to calculate the time of execution of a Perl script

2010-01-10T06:40:00.001-08:00

Just add the following line any where in your Perl script and it will print its time of execution right at the end:

# This calculates the time of execution of the Perl script.
END {warn "\nTime of execution - ", time - $^T, " second(s)\n"}

Connecting to MySQL Database through PERL

2009-04-16T12:49:00.001-07:00

FAQ: How to connect to MySQL database through PERL.

SOLUTION:
1. Install MySQL database. MySQL community server comes free of cost and is distributed under GNU General Public License.

2. I would instead recommend installing a package called WAMP server which provides MySQL community server, Apache server and PHP. It also provides many effective tools like PHPMyAdmin which can be used for database administration. Also WAMP server comes free of cost and is distributed under GNU General Public License.

3. To check if the MySQL server is running, execute:
telnet 3306
E.G: # telnet 127.0.0.1 3306

4. I would also recommend you to also install SQLYog. It is a very light and effective tool to monitor and manage MySQL database. Again it also comes free of cost and is distributed under GNU General Public License.

5. Create a database in MySQL, a non-root user and give it a password.

6. Install ‘DBI’ perl module through ‘PPM’

7. Install ‘DBD::Mysqlpp” perl module through ‘PPM’

8. You are all set to connect to MySQL database. While connecting make sure that database is already created and you are connecting through a valid user and with correct credentials. To see a sample script execute following on command prompt:
# perldoc DBD::Mysqlpp

REFERENCES:
1. http://dbi.perl.org/
2. # perldoc DBD::Mysqlpp

AUTHOR: Parag Kalra
Email-ID: paragkalra@gmail.com

Using Regular expressions in PERL - Script1

2009-03-21T07:46:00.000-07:00

#!/usr/bin/perl
#===============================================================================
#
# FILE: test2.pl
#
# USAGE: ./test2.pl
#
# DESCRIPTION: Weekly Test2: The script has a paragraph defined at it's start.
# The script reads the each word of the paragraph and processes it
# to check following conditions:
#
# 1. has an 'a'
# 2. starts with an 'a'
# 3. has 'th'
# 4. has an 'a' or an 'A'
# 5. has a '*' in it
# 6. starts with an 'a' or an 'A'
# 7. has both 'a' and 'e' in it
# 8. has an 'a' followed by an 'e' somewhere in it
# 9. does not have an 'a'
# 10. does not have an 'a' nor 'e'
# 11. has an 'a' but not 'e'
# 12. has at least 2 consequtive vowels (a,e,i,o,u)
# 13. has at least 3 vowels
# 14. has at least 6 characters
# 15. has at exactly 6 characters
# 16. all the words with either 'aba' or 'ada' in them
# 17. all the words with either 'aba' or 'eda' in them
# 18. has a double character (e.g. 'oo')
# 19. for every word print the first vowel
#
#
# OPTIONS: ---
# REQUIREMENTS: ---
# BUGS: ---
# NOTES: ---
# AUTHOR: Parag Kalra, paragkalra@gmail.com
# COMPANY: PERSISTENT SYSTEMS LTD, http://www.persistentsys.com/
# VERSION: 1.0
# CREATED: 3/19/2009 2:11:51 PM
# REVISION: ---
#===============================================================================

use Acme::Comment;

# Declaring the Paragraph
$mypara="Finish each day and be done with it. You have done what you could. Some blunders and absurdities no doubt crept in; forget them as soon as you can. Tomorrow is a new day; begin it well, with no pre-conceived notions and with too high a spirit so as to be able to hold back your old stuff. India is great. I love star*star. Vowels combination: axxiyywwrroo arixeupoq abajan abaada adamant abacuss edaiot Apple MAP Axe Gooogle PEANUT PqRs AIm";

# Spliting the string by space characater to store the words of the para into an array.
@para_words=split /\s+/, $mypara;

@vowels=qw/a e i o u/;

#---------------------------------------------------------------------------
# Processing each word of the array with regular expressions.
#---------------------------------------------------------------------------
foreach ( @para_words ) {
#print "Processing: $_ \n";

# 1
# Words containing 'a'
if ( $_ =~ m{a+} ) {
push @words_with_a, $_;

# Words containing 'a' but not 'e'
# As of now not working
#if ( $_ =~ m{[^e]} ) {
#push @words_having_a_not_e, $_;
#}
}

# 3
# Words having 'th'
if ( $_ =~ m{(th)+} ) {
push @words_with_th, $_;
}

# 4
# Words having either 'a' or 'A'
if ( $_ =~ m{a+}i ) {
push @words_with_Aa, $_;
}

# 5
# Words having star
if ( $_ =~ m{\*} ) {
push @words_with_star, $_;
}

# 6
# Words starting with 'a' or 'A'
if ( $_ =~ m{^a+}i ) {

push @words_starting_with_Aa, $_;

# 2
# Words starting with 'a'
if ( $_ =~ m{^a+} ) {
push @words_starting_with_a, $_;
}
}

# 7
# Words containing both 'a' and 'e'
if ( $_ =~ m{e+} && $_ =~ m{a}) {
push @words_having_both_ae, $_;
}

# 8
# Words in which 'a' is followed by 'e'
if ( $_ =~ m{(ea)+} ) {
push @words_having_a2e, $_;
}

# 9
# Words which doesnot have 'a'
# As of now not working with carat
if ( $_ !~ m{a} ) {
push @words_without_a, $_;
}

# Multiline comment
/*
if ( $_ !~ m{a+} ) {
push @words_without_a, $_;

if ( $_ !~ m{e+} ) {
push @words_without_a_e, $_;
}
}
*/

# 10
# Words except 'a' and 'e'
if ( $_ !~ m{e+} && $_ !~ m{a+} ) {

push @words_without_a_e, $_;

}

# 11
# Words having 'a' not having 'e'
if ( ($_ !~ m{e}) && ($_ =~ m{a}) ) {
push @words_having_a_not_e, $_;
}

# 12
# Words having 2 consecutive vowels
$var=$_;
foreach ( @vowels ) {
$v=$_;
#print "Current vowel: $v";

for ( $i=0; $i<5 ; $i++ ) {
#print "$v$vowels[$i] \n";
#if ( $var =~ /(($v){1})($vowels[$i]{1})/ ) {

# Matching the pattern for consecutive vowels
if ( $var =~ /$v$vowels[$i]/i ) {
#print "$var \n";
push @words_having_2_con_vowels, $var;
}

}
}

# 13
# Words containing at least 3 vowels
if (tr/aeiouAEIOU/aeiouAEIOU/ >= 3 ) {
push @words_having_3_vowels, $_;
}

# Pattern for matching 3 vowels
#for ( $p=0; $p<5 ; $p++ ) {
#for ( $q=0; $q<5 ; $q++ ) {
#for ( $r=0; $r<5 ; $r++ ) {
#if ( $var =~ /^(.*)($vowels[$p])(.*)$vowels[$q](.*)$vowels[$r](.*)$/ ) {
#if( grep $var, @words_having_3_vowels){
#push @words_having_3_vowels, $var;
#}
#}
#}
#}
#}

# Pattern for matching 3 consecutive vowels
# As of now under-construction
#if ( $_ =~ /[aeiou]{3,}/ ) {
# push @words_having_3_vowels, $_;
#}

# 14
# Words having at least 6 characters
if ( $_ =~ /(.){6,}/ ) {
push @words_with_atl_6_chs, $_;
}

# 15
# Words having exactly 6 characters
# As of now not working for '-'
#if ( $_ =~ /\b(.){6}\b/ ) {
if ( $_ =~ /^(.){6}$/ ) {
push @words_with_6_chs, $_;
}

# 16
# Words containing either 'aba' or 'ada'
if ( $_ =~ m{(aba)|(ada)}) {
push @aba_ada, $_;
}

# 17
# Words containing either 'aba' or 'eda'
if ( $_ =~ m{(aba)|(eda)}) {
push @aba_eda, $_;
}

# 18
# Words having identical adjoining characters
if ( $_ =~ /(.)\1/ ) {
push @words_with_2_chs, $_;
}

# 19
#---------------------------------------------------------------------------
# Printing the word and it's first vowel if at all it contains
#---------------------------------------------------------------------------
$mystring = $_;
#@chars = map substr( $mystring, $_, 1), 0 .. length($mystring) -1;
@chars = unpack('a'x length($mystring), $mystring);

if($mystring !~ /[aeiou]/i){
print "'$mystring' has no vowel \n";
} else {
foreach(@chars){
#print "$_ \n";
if($_ =~ /[aeiou]/i){
print "First vowel of '$mystring': $_ \n";
last;
}

}
}

}

print "\n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words containing 'a': @words_with_a \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words starting with 'a': @words_starting_with_a \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words containing 'th': @words_with_th \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words containing either 'A' or 'a': @words_with_Aa \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words containing star: @words_with_star \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words starting with 'A' or 'a': @words_starting_with_Aa \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words containing both 'a' and 'e': @words_having_both_ae \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words in which 'a' is followed by 'e': @words_having_a2e \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words which doesn't have 'a': @words_without_a \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words except 'a' and 'e': @words_without_a_e\n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words having 'a' but not 'e': @words_having_a_not_e \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words having 2 consecutive vowels: @words_having_2_con_vowels \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words having at least 3 vowels: @words_having_3_vowels \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words having at least 6 characters: @words_with_atl_6_chs \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words having exactly 6 characters: @words_with_6_chs \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words having 'aba' and 'ada': @aba_ada \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words having 'aba' and 'eda': @aba_eda \n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "Words having 2 similar and adjoint characters: @words_with_2_chs\n";
print "----------------------------------------------------------------------------------------------------------------------------------------\n";
print "\n";

Script to ask the numbers from user as a input and return the numbers which are above average.

2009-02-11T05:43:00.000-08:00

#!/usr/bin/perl
#===============================================================================
#
# FILE: above_avg.pl
#
# USAGE: perl above_avg.pl
#
# DESCRIPTION: Script to ask the numbers from user as a input and return the numbers which are above average.
#
# OPTIONS: ---
# REQUIREMENTS: ---
# BUGS: ---
# NOTES: ---
# AUTHOR: Parag Kalra, paragkalra@gmail.com, www.paragkalra.com (),
# COMPANY: As of now Persistent System LTD, www.persistentsys.com
# VERSION: 1.0
# CREATED: Wednesday 11 February 2009 07:06:21 IST
# REVISION: ---
#===============================================================================

print "Please enter the numbers: \n";
@nums=;

@more_avg=&above_avg(@nums);

#=== FUNCTION ================================================================
# NAME: above_avg
# PURPOSE: To calculate numbers above average
# PARAMETERS: ????
# RETURNS: ????
# DESCRIPTION: ????
# THROWS: no exceptions
# COMMENTS: none
# SEE ALSO: n/a
#===============================================================================
sub above_avg {

print "You have entered following numbers: \n ";
print "@_ \n";
$avg_value=&avg(@_);

print "Numbers greater than average - $mean are: \n";

foreach (@_) {
if ($_ > $avg_value) {
#@return_more=(@return_more,$_);
push(@return_more,$_);

}

}

print " @return_more \n";
}

#=== FUNCTION ================================================================
# NAME: avg
# PURPOSE: To calculate mean value
# PARAMETERS: ????
# RETURNS: ????
# DESCRIPTION: ????
# THROWS: no exceptions
# COMMENTS: none
# SEE ALSO: n/a
#===============================================================================
sub avg {
$sum=0;
$count=0;
foreach (@_) {
$sum=$sum+$_;
$count=$count+1;
}
$mean=$sum / $count;
print "Total numbers entered: $count \n";
print "Sum of numbers: $sum \n";
print "Mean of numbers: $mean \n";
$mean;
}

Using GVIM as a PERL IDE !!!

2009-02-04T08:27:00.000-08:00

People who do extensive PERL scripting on UNIX and love "vi' editor. Here's some interesting stuff for you:

http://www.vim.org/scripts/script.php?script_id=556

After unzipping it in the folder "$HOME/.vim/", read the file "$HOME/.vim/README.perlsupport"

Using variables in bash script.

2009-02-02T09:04:00.000-08:00

#!/bin/bash
#===============================================================================
#
# FILE: vars_bash.sh
#
# USAGE: ./vars_bash.sh
#
# DESCRIPTION: Using variables in bash script.
#
# OPTIONS: ---
# REQUIREMENTS: ---
# BUGS: ---
# NOTES: ---
# AUTHOR: Parag Kalra (), paragkalra@gmail.com, www.paragkalra.com
# COMPANY: As of now Persistent System LTD, www.persistentsys.com
# VERSION: 1.0
# CREATED: Sunday 01 February 2009 11:16:38 IST IST
# REVISION: ---
#===============================================================================

echo "uninitialized_variable = $uni_var"

null_variable=
echo "null_variable = $null_variable"

let "num_var2 += 2"
echo "$num_var2"

num_var1=1
let "num_var1 += 4"
echo "$num_var1"

#-------------------------------------------------------------------------------
# Unsetting a variable
#-------------------------------------------------------------------------------
num_var=13
echo "$num_var"
unset num_var
echo "$num_var"

#-------------------------------------------------------------------------------
# Different ways a variable can be assigned
#-------------------------------------------------------------------------------
a=13;
echo $a

let a=a+13
echo $a

echo "Enter the value you want to assign to variable a: "
#read a

for a in 1 2 3
do
echo $a
done

list1=`ls -l`
echo $list1

list2=$(ls -l)
echo $list2

#-------------------------------------------------------------------------------
# Converting integers to strings and vice-versa
#-------------------------------------------------------------------------------
a=1234
echo $a

let a=a+1
echo $a

a=${a/35/TF}
echo $a

a=${a/TF/13}
echo $a

Using positional parameters in bash scripts

2009-02-02T08:27:00.000-08:00

#!/bin/bash
#===============================================================================
#
# FILE: posi_param.sh
#
# USAGE: ./posi_param.sh 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
#
# DESCRIPTION: To exhibit usage of positional parameters
#
# OPTIONS: ---
# REQUIREMENTS: ---
# BUGS: ---
# NOTES: ---
# AUTHOR: Parag Kalra (), paragkalra@gmail.com, www.paragkalra.com
# COMPANY: As of now Persistent System LTD, www.persistentsys.com
# VERSION: 1.0
# CREATED: Sunday 01 February 2009 01:35:54 IST IST
# REVISION: ---
#===============================================================================

echo -e "\n \n"

echo "The arguments passed are: $*"
echo -e "Total number of arguments passed are: $# \n \n"

echo $1
echo $2
echo $3
echo $4
echo $5
echo $6
echo $7
echo $8
echo $9

echo -e "\n \n"
#-------------------------------------------------------------------------------
# Accessing positional parameters with curly braces produce unexpected result
#-------------------------------------------------------------------------------
echo $10
echo $11
echo $12
echo $13
echo $14
echo $15
echo -e "\n \n"

#-------------------------------------------------------------------------------
# This is the way to access double digit positional parameters
#-------------------------------------------------------------------------------
echo ${10}
echo ${11}
echo ${12}
echo ${13}
echo ${14}
echo ${15}
echo -e "\n \n"

#-------------------------------------------------------------------------------
# This is strange
#-------------------------------------------------------------------------------
for a in 1 2 3 4 5
do
echo $`echo $a`
done
echo -e "\n \n"

#-------------------------------------------------------------------------------
# and it still remains strange
#-------------------------------------------------------------------------------
for a in 1 2 3 4 5
do
echo "$`echo $a`"
done
echo -e "\n \n"

#-------------------------------------------------------------------------------
# Shiting the positional parameters
#-------------------------------------------------------------------------------
#: << COMMENTED
echo "Shifting positional parameters.."
until [ -z $1 ]
do
echo $1
shift
done
echo -e "\n \n"
#COMMENTED

#-------------------------------------------------------------------------------
# Shiting the positional parameters by 5 characters
#-------------------------------------------------------------------------------
echo "Shifting positional parameters by 4 characters.."
until [ -z $1 ]
do
echo $1
shift 4
done
echo -e "\n \n"

Script to mount multiple isos.

2009-01-30T12:49:00.000-08:00

 #!/bin/bash
#===============================================================================
#
#          FILE:  deand.sh
#
#         USAGE:  ./deand.sh
#
#   DESCRIPTION: To mount partition and then the iso
#
#       OPTIONS:  ---
#  REQUIREMENTS:  ---
#          BUGS:  ---
#         NOTES:  ---
#        AUTHOR:  Parag Kalra (), paragkalra@gmail.com, www.paragkalra.com
#       COMPANY:  As of now Persistent System LTD, www.persistentsys.com
#       VERSION:  1.0
#       CREATED:  Thursday 29 January 2009 08:04:14  IST IST
#      REVISION:  2
#===============================================================================

#-------------------------------------------------------------------------------
#   Creating "/temp" if it doesn't exist
#-------------------------------------------------------------------------------
if [ ! -d /temp ]
then
    mkdir /temp
fi

#-------------------------------------------------------------------------------
#   Creating /iso if it doesn't exist
#-------------------------------------------------------------------------------
if [ ! -d /iso ]
then
    mkdir /iso
fi

echo " "

#-------------------------------------------------------------------------------
#   Mounting partition and then the iso
#-------------------------------------------------------------------------------
if ! mount | grep sda1
then
    echo -e "Mounting partition\n"   
    mount /dev/sda1 /temp
else
    echo -e "Partition sda1 already mounted. \n"
fi


#===  FUNCTION  ================================================================
#          NAME:  isomount()
#   DESCRIPTION:  To mount the respective iso
#    PARAMETERS:  isoname
#       RETURNS:  nothing
#===============================================================================
function isomount
{
    echo -e "You have selected $1 hence mounting $1 iso\n"
    mount -o loop /temp/root/linuxcbt-$1/linuxcbt-$1.iso /iso
}
# ----------  end of function isomount  ----------

echo -e "Please enter the ISO you want to mount: \n1. rhel4\n2. sendmail\n3. samba\n4. security\n5. rhel5dvd\n6. postfix\n7. qmail"
read iso

case $iso in

rhel4)
isomount rhel4
;;

samba)
isomount samba
;;

security)
isomount security
;;

sendmail)
isomount sendmail
;;

postfix)
isomount postfix
;;

qmail)
isomount qmail
;;

rhel5dvd)
echo -e "You have selected $iso hence trying to mount $iso \n"
if  ! mount | grep rhel5iso  
then
    echo -ec"Mounting $iso \n"
    mount -o loop /temp/root/RHEL-5.1-i386-DVD.iso /share/rhel5iso
else
    echo -e "$iso already mounted. \n"
fi
;;

esac  

 # --- end of case ---

BASH script to copy a remote database !!!

2009-01-18T09:28:00.000-08:00

#!/bin/bash
#===============================================================================
#
# FILE: db_sync.sh
#
# USAGE: ./db_sync.sh
#
# DESCRIPTION: To sync the remote database
#
# OPTIONS: ---
# REQUIREMENTS: ---
# BUGS: ---
# NOTES: -----
# AUTHOR: Parag Kalra (), paragkalra@gmail.com, www.paragkalra.com
# COMPANY: As of now Persistent System LTD, www.persistentsys.com
# VERSION: 1.0
# CREATED: Sunday 18 January 2009 12:44:49 IST IS
# REVISION: ---
#===============================================================================

#-------------------------------------------------------------------------------
# Storing username, password & logfile in a variable
#-------------------------------------------------------------------------------
myuser=some_user
mypasswd=some_password
mylog=/var/log/projects/db_sync.log

#-------------------------------------------------------------------------------
# Executing a SQL file to create & drop local databases.
#-------------------------------------------------------------------------------
echo "Executing SQL file - `date`" > $mylog
mysql --verbose --user=$myuser --password=$mypasswd --host=localhost < /data/projects/mysql/alter_dbs.sql #---------------------------- #Dumping the remote database on the local setup #---------------------------- echo "Dumping remote mysql databases- `date`" >> $mylog
mysqldump --verbose --user=$myuser --password=$mypasswd --host=www.paragkalra.com some_database > /data/databases/pkc_db_`date +%F`.sql

#-------------------------------------------------------------------------------
# Importing the database
#-------------------------------------------------------------------------------
echo "Importing the database - `date`" >> $mylog
mysql --verbose --user=$myuser --password=$mypasswd some_database < /data/databases/pkc_db_`date +%F`.sql
echo "Export - Import of database complete - `date`" >> $mylog

BASH IDE plugin for GVIM

2008-10-19T13:31:00.000-07:00

http://www.linux.com/feature/114359

Download location of plugin:
http://www.vim.org/scripts/script.php?script_id=365

Or just execute the script given below to download and install the IDE.
(Script "unit" tested on Debian & OpenSUSE but should work out of the box on any other NIX flavor .)

Couldn't test this script on FreeBSD.
(as couldn't find "gvim" port under ftp://ftp.freebsd.org/pub/FreeBSD/ports)

#!/bin/bash
#===============================================================================
#
# FILE: gvim_bash_ide.sh
#
# USAGE: ./gvim_bash_ide.sh OR sh gvim_bash_ide.sh
#
# DESCRIPTION: The scripts downloads the bash ide plugin for gvim, extracts it & copies it under ~/.vim
#
# OPTIONS: ---
# REQUIREMENTS: gvim
# BUGS: ---
# NOTES: The script assumes gvim installed. Revision 1 of this file was tested on Debian 4.0 R2 & OpenSUSE 10.3.
#
# AUTHOR: Parag Kalra, paragkalra@gmail.com
# COMPANY: As of now (19-Oct-08) Persistent Systems LTD
# VERSION: 1.0
# CREATED: Sunday 19 October 2008 09:40:49 IST IST
# REVISION: 1
#===============================================================================

SRCID=9304

if [ -f /etc/debian_version ]
then
echo -e "\nSeems as if you are using Debian. Please make sure that gvim is installed. It comes packed with DVD ... \n"
elif [ -f /etc/SuSE-release ]
then
echo -e "\nSeems as if you are OpenSUSE or may be SLES. Please make sure that gvim is installed. It comes packed with DVD ...\n"
elif [ -f /etc/redhat-release ]
then
echo -e "\nSeems as if you are using Redhat or Fedora. Please make sure that gvim is installed. \n"
else
echo -e "\nPlease make sure that gvim is installed before adding bash ide plugin ... \n"
fi

if [ -d ~/.vim ]
then
echo -e "Directory ~/.vim already exists ... \n"
else
echo -e "Creating vim directory under user's home directory ... \n"
mkdir ~/.vim
echo -e "Navigating into ~/.vim \n"
cd ~/.vim
fi

echo -e "Downloading bash ide plugin for gvim from www.vim.org ... \n"
wget --verbose -P~/.vim http://www.vim.org/scripts/download_script.php?src_id=$SRCID -O bash-support.zip

#As of now this script downloads latest bash ide plugin. To download the latest plugin:
# 1. get the latest "src_id" from http://www.vim.org/scripts/script.php?script_id=365
# 2. and change the the "SRCID"

echo -e "Navigating into ~/.vim \n"
cd ~/.vim

echo -e "Unzipping bash ide plugin for gvim ... \n"
unzip bash-support.zip

echo -e "\nDeleting unused files ... \n"
rm -rf bash-support.zip

if [ -f ~/.vim/plugin/bash-support.vim ]
then
echo -e "Seems as if all went good. Open gvim and check the bash ide plugin ... \n"
else
echo -e "Something got screwed. Figure it out yourself ... \n"
fi

Just go through it and let me know if you happen to come across any bug in it. eMail me at paragkalra@gmail.com

Shell Script to show disk space, logged in users and memory usage.

2008-10-11T04:27:00.000-07:00

#!/usr/bin/sh
#Author: Parag Kalra
#Date: 11th October, 2008

function menu {

clear
echo
echo -e "\t\t\tSys Admin Menu\n"
echo -e "\t1. Display disk space"
echo -e "\t2. Display logged on users"
echo -e "\t3. Display memory usage"
echo -e "\t0. Exit menu\n\n"
echo -en "\t\tEnter option: "
read -n 1 option

}

function diskspace {
clear
df -k
}

function users {
clear
who
}

function memusage {
clear
cat /proc/meminfo
}

while [ 1 ]
do
clear
menu

case $option in
0)
echo
break;;
1)
diskspace;;
2)
users;;
3)
memusage;;
*)
echo "Wrong Option"
esac

echo "Hit any key to continu!"
read -n 1 line
done

Just go through it and let me know if you happen to come across any bug in it. eMail me at paragkalra@gmail.com

Shell-script to add comments and html tags in php files.

2008-06-14T00:18:00.000-07:00

I am sometimes required to write PHP scripts and I find typing tags and comments quite boring. Look what I have done. I have written a fully automated script that will make you job very easy and you can easily place tags and comments into your php scripts.

Just go through it and let me know if you happen to come across any bug in it. eMail me at paragkalra@gmail.com

#!/bin/bash
#Author: Parag Kalra
#Date: 14th June, 2008
#Name: php-tags.sh
#Usage: ./php-tags.sh
#Purpose: To automatically add comments and html tags.

# BEGINNING

echo "Enter the name of the shell script: "
read SHNAME

echo "Enter the purpose of this shell script: "
read SHPURPOSE

export SHDATE #='$SHDATE'
export SHNAME #='$SHNAME'
export SHPURPOSE #='$SHPURPOSE'

touch $SHNAME

echo "html tag" >> $SHNAME
echo "head tag, title tag, title end tag, head end title>" >> $SHNAME
echo "body tag" >> $SHNAME

echo "php start tag" >> $SHNAME

echo "#!/bin/bash" >> $SHNAME
echo "#Author: Parag Kalra" >> $SHNAME
echo "#Date: $SHDATE" >> $SHNAME
echo "#Name: $SHNAME" >> $SHNAME
echo "#Usage: ./$SHNAME" >> $SHNAME
echo "#Purpose: $SHPURPOSE" >> $SHNAME

echo "php end tag" >> $SHNAME

echo "body end tag" >> $SHNAME
echo "html end tag" >> $SHNAME

#END OF SCRIPT

Functions in Shell-Scripting => Part 1

2008-06-02T14:16:00.000-07:00

#!/bin/bash
#Author: Parag Kalra
#Date: 3rd June, 2008
#Name: func1.sh
#Usage: ./func1.sh
#Purpose: To illustrate usage of functions in Shell Scripts.

JUST_A_SECOND=1
REPEATS=3

funky()
{
echo "This is a just funky function...not that exciting..."
}

fun()
{
echo "The real fun starts now."
i=0
sleep $JUST_A_SECOND

while [ $i -lt $REPEATS ]
do
echo "FUNCTIONS R FUN"
echo
let "i+=1"
done
}

funky
fun

The output of above script is:

This is a just funky function...not that exciting...
The real fun starts now.
FUNCTIONS R FUN

FUNCTIONS R FUN

FUNCTIONS R FUN

Just go through it and let me know if you happen to come across any bug in it. eMail me at paragkalra@gmail.com

Concept of Sub-Shells - Part 2

2008-06-01T07:46:00.000-07:00

Variables defined in a subshell are "local variables. Also variable operations inside a subshell, even to a GLOBAL variable do not affect the value of the variable outside the subshell! Kindly refer to the script given below:

#!/bin/bash
#Author: Parag Kalra
#Date: 1st June, 2008
#Name: glo-var-sub-shell.sh
#Usage: ./glo-var-sub-shell.sh
#Purpose: To illustrate concept of global variables within sub-shells

global_variable=
outer_num=12

echo "Outside Subshell"
echo "global_variable=$global_variable"
echo "outer_num=$outer_num "
echo " "

(

echo "Inside Subshell"
inner_variable=26
let "outer_num+=1"
echo "global_variable=$global_variable"
echo "outer_num=$outer_num"
echo "inner_variable=$inner_variable "
echo " "
)

echo "Again Outside of Subshell"
echo "outer_num=$outer_num"
echo "inner_variable=$inner_variable"

# END OF SCRIPT

The output of above script is:
Outside Subshell
global_variable=
outer_num=12

Inside Subshell
global_variable=
outer_num=13
inner_variable=26

Again Outside of Subshell
outer_num=12
inner_variable=

Just go through it and let me know if you happen to come across any bug in it. eMail me at paragkalra@gmail.com

Concept of Sub-Shells - Part1

2008-05-30T12:00:00.000-07:00

First & foremost to create sub-shells within a script you need to use round brackets "( )". Value assigned to outermost shell is always 0. As you move inside sub-shells their values keep on increasing by 1 as depicted in the example shown below:

#!/bin/bash
#Author: Parag Kalra
#Date: 31st May, 2008
#Name: subshell1.sh
#Usage: ./subshell1.sh
#Purpose: To illustrate values assigned to sub-shells

echo "We are outside the subshell."
echo "Subshell level OUTSIDE subshell = $BASH_SUBSHELL"

(
echo "We are inside first subshell."
echo "Subshell level INSIDE first subshell = $BASH_SUBSHELL"

(
echo "Inside second sub-shell"
echo "Subshell level INSIDE second subshell = $BASH_SUBSHELL"

(
echo "Inside third sub-shell"
echo "Subshell level INSIDE third subshell = $BASH_SUBSHELL"
)

)

)

echo "We are again outside all the subshells."
echo "Subshell level OUTSIDE subshell = $BASH_SUBSHELL"

#END OF SCRIPT

The output of above script is:

We are outside the subshell.
Subshell level OUTSIDE subshell = 0
We are inside first subshell.
Subshell level INSIDE first subshell = 1
Inside second sub-shell
Subshell level INSIDE second subshell = 2
Inside third sub-shell
Subshell level INSIDE third subshell = 3
We are again outside all the subshells.
Subshell level OUTSIDE subshell = 0

Shell-Script to add headers to another Shell-Script

2008-05-29T14:35:00.000-07:00

I write Shell-Scripts day in day out. For each and every shell-script I need to place following headers at the beginning of it. For e.g. consider following header:

#!/bin/bash
#Author:
#Date:
#Name:
#Usage:
#Purpose:

I have prepared a shell-script to automatically add the above header to the newly created shell-script. Just go through it and let me know if you happen to come across any bug in it:

#!/bin/bash
#Author: Parag Kalra
#Date: 30th May, 2008
#Name: shell-script-header.sh
#Usage: ./shell-script-header.sh
#Purpose: To add headers to shell-scripts

echo "Enter the date: "
read SHDATE

echo "Enter the name of the shell script: "
read SHNAME

echo "Enter the purpose of this shell script: "
read SHPURPOSE

export SHDATE #='$SHDATE'
export SHNAME #='$SHNAME'
export SHPURPOSE #='$SHPURPOSE'

touch $SHNAME

echo "#!/bin/bash" >> $SHNAME
echo "#Author: Parag Kalra" >> $SHNAME
echo "#Date: $SHDATE" >> $SHNAME
echo "#Name: $SHNAME" >> $SHNAME
echo "#Usage: ./$SHNAME" >> $SHNAME
echo "#Purpose: $SHPURPOSE" >> $SHNAME

#END OF SCRIPT