I have a unique problem with my firefox – and as far as I know I am the only one who has this issue. Firefox is very slow to scroll pages that has a fixed background image. Ajaxian is an example of such a site. This problem exists in all profiles of Firefox(not a extension issue) – but it works without any issue in other browsers – like Konqueror. Does anyone else have this issue?

This problem is only present in my desktop – a Fedora 8/KDE with Firefox 3.0.8 – with nVidia drivers installed. No issues on my laptop(Kubuntu). I still have no idea what’s causing this. But I did solve the issue.

Greasemonkey Script

I created a greasemonkey script that disables fixed background anywhere in the page. Changes all fixed background images to normal background image(scrolls with the page). Here is the script if anyone has the same issue.

Fixed Background Remover Greasemonkey User Script

Remember, this is a beta version – let me know if you find any issues with the script.

If you are using Konqueror and have not used custom service menus, you are missing out. Just like the Nautilus Scripts in Nautilus, Konqueror also has the ability to customize the context menus. This post will show you how to do it.

We are going to create two different kind of service menus – one will create an item in the action part of the right click menu. The next type will create a submenu in the ‘actions’ menu with multiple menu items. Hopefully, you will get an idea about how to do it by yourself.

Single Item Service Menu

This service menu will create a menu item in the Action section of the context menu for all ISO files. For this to work as intended, the mimetype for ISO file must be application/x-iso .

• Open ~/.kde/share/apps/konqueror/servicemenus folder
• Create a file with the name ‘PlayISO.desktop’ – the name can be anything – but the extension must be ‘.desktop’
• Enter the following content…

[Desktop Entry]
ServiceTypes=application/x-iso
Actions=PlayISOInXine

[Desktop Action PlayISOInXine]
Name=Play ISO File in Xine
Icon=player_play
Exec=xine -pq --no-splash dvd:/%f

Now lets see a line by line explanation of the code.

[Desktop Entry]

Start the file with this line.

ServiceTypes=application/x-iso

This decides which all file types must this service menu be shown to. You can find the mimetype for various files by taking Control Center > KDE Components > File Associations. Then search for the extension in the given text field.

Actions=PlayISOInXine

Name of the action – this will be defined in the next line

[Desktop Action PlayISOInXine]

The definition of the ‘PlayISOInXine’ action goes here.

Name=Play ISO File in Xine

The text to be shown in the menu item.

Icon=player_play

The icon to be used in the menu. The icon can be an absolute path or the file name of an image in your current theme(for example, if you are using Crystal SVG theme, then the images you can use is in the folder ‘/usr/share/icons/crystalsvg/16×16/actions’).

Exec=xine -pq –no-splash dvd:/%f

The command to be executed when the menu item is clicked. The %f stands for the full name of the file. The other options are listed in the documentation.

This is the end result…

Submenu Service Menu

This sample will give you the option to convert the selected html file to a plain text file or a compressed archive. The code looks like this…

[Desktop Entry]
ServiceTypes=text/html
Actions=convertToText;convertToZip
X-KDE-Submenu=Convert

[Desktop Action convertToText]
Name=Convert To Text
Icon=txt
Exec=lynx -dump "%f" > "`dirname "%f"`/`basename "%f" ".html"`.txt"

[Desktop Action convertToZip]
Name=Compress as Zip
Icon=tar
Exec=zip "`dirname "%f"`/`basename "%f" ".html"`.zip" "%f"

Again, a line by line explanation…

[Desktop Entry]

You know.

ServiceTypes=text/html

This is only for HTML files – so we specify the mimetype as text/html

Actions=convertToText;convertToZip

We have two different actions instead of just one as in the last case. So we provide the name of both actions separated by a ‘;’.

X-KDE-Submenu=Convert

This will make sure its shown in a submenu – and that the name of the submenu is Convert.

[Desktop Action convertToText]

Defining the first action – convertToText

Name=Convert To Text

The label of the menu item

Icon=txt

And its icon

Exec=lynx -dump “%f” > “`dirname “%f”`/`basename “%f” “.html”`.txt”

This command will convert a html file to a text file and put the resulting file in the same folder as the html file.

[Desktop Action convertToZip]

Defining the next action – convertToZip

Name=Compress as Zip

Label

Icon=tar

And Icon

Exec=zip “`dirname “%f”`/`basename “%f” “.html”`.zip” “%f”

The command to compress the html file as a zip file.

If done correctly, it should look something like this…

Related Links

• Desktop File Documentation
• Do-it-yourself Konqueror commands
• Collection of Service Menu Scripts
• GUI Service Menu Editor

The script uses ‘mysqldump’ command to backup the data. That means that the backups are in the SQL dump format. The dumps of all the databases that are backed up are compressed and stored in the destination folder. They will be named in this format – YYYY-MM-DD.tar.gz.

Configuration File

This script reads a configuration file named ‘dbbackup.config’ and backups all the databases specified in that file to another location in the same system. This configuration file must be in the same folder as the perl script. The configuration file format is given below…

Data
Project_Nexty
App_activecollab
# Unwanted_DB - commented - will not be backedup
binco
binnyva

The Perl Script

#!/usr/bin/perl
# Backups all the databases specified in the dbbackup.config file

$backup_folder = '/var/Backup/Special/Databases'; #EDIT THIS LINE

use File::Basename;
my $config_file = dirname($0) . "/dbbackup.config";
my @databases = removeComments(getFileContents($config_file));

chdir($backup_folder) or die("Cannot go to folder '$backup_folder'");

my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time);
$year += 1900;
$mon++;
#Zero padding
$mday = '0'.$mday if ($mday<10);
$mon = '0'.$mon if ($mon<10);

my $folder = "$year-$mon-$mday";
mkdir($folder) or die("Cannot create a folder called '$folder'");

foreach my $database (@databases) {
	next if ($database eq '');
	chomp($database);

	my $table = '';
	if(index($database,' ')+1) { #Get just 1 table in the database - if there is a ' '(space) in the db name
		my @parts = split(' ',$database);
		$database = $parts[0];
		$table = $parts[1];
	}

	print "Backing up $database ... ";

 	my $file = $database;
 	$file .= '_' . $table if($table ne '');
 	$file .= ".sql";

 	`mysqldump -u root $database $table > $folder/$file`;

	print "Done\n";
}
print "Compressing the folder ... ";
`tar -czf $folder.tar.gz $folder/`;
print "Done\nRemoving Folder ... ";
`rm -rf $folder`;
print "Done\n\n";

sub getFileContents {
	my $file = shift;
	open (FILE,$file) || die("Can't open '$file': $!");
	my @lines=<FILE>;
	close(FILE);

	return @lines;
}

sub removeComments {
	my @lines = @_;

	@cleaned = grep(!/^\s*#/, @lines); #Remove Comments
	@cleaned = grep(!/^\s*$/, @cleaned); #Remove Empty lines

	return @cleaned;
}

If you need, you can set this script as a cron job – this will make sure that you don’t have to worry about the backup.

This script will backup the specified files to another computer on your network. You can also use this to send your files to a remote server. This script compliments the last Rsync Backup script. Its possible to combine both the script together, I prefer to keep them separate.

The Setup

For this to work, you need to have a password-less login system over ssh. You should configure the remote system to accept your credentials by giving your public key to the remote server. If you are not sure how to do that, just leave a comment and I’ll make a post on how to set it up.

The configuration file is the same format as the one used in the last Rsync script. But in this case, the file name will be ‘rsyncnetworkbackup.config‘.

The Code

#!/usr/bin/perl

#The folder on the remote system that must be used to store the data
$backup_folder = '/home/neo/Backup'; #Final '/' must NOT be there.
# The user for whom we have set up the key based login
$backup_user = 'neo';
# The IP address/domain name of the remote system.
$backup_server = '192.168.0.30';

use File::Basename;
my $config_file = dirname($0) . "/rsyncnetworkbackup.config";
my @all_locations = removeComments(getFileContents($config_file));

foreach my $folder_locations (@all_locations) {
	my($folder,$backup_location) = split(/\s+/,$folder_locations);

	print "Backing up $folder to $backup_location ... ";
	`rsync -avze ssh $folder $backup_user\@$backup_server:\"$backup_folder/$backup_location\"`;
	print "Done\n";
}

sub getFileContents {
	my $file = shift;
	my @lines;

	open (FILE,$file) || die("Can't open '$file': $!");

	@lines=<FILE>;
	close(FILE);
	return @lines;
}

sub removeComments {
	my @lines = @_;

	@cleaned = grep(!/^\s*#/, @lines); #Remove Comments
	@cleaned = grep(!/^\s*$/, @cleaned); #Remove Empty lines

	return @cleaned;
}

All programmers have their own customized backup solutions. I have six. Yes, six! Five to backup files and one to backup database tables. And I am not counting version control or other backup systems built into the tools I use. Anyway, in the first post of the shell scripts series, let me introduce you to my Rsync based local backup solution.

Configuration File

This script reads a configuration file named ‘rsyncbackup.config’ and backups all the folders specified in that file to another location in the same system. This configuration file must be in the same folder as the perl script. The configuration file format is given below…

#Notes - do NOT include the last '/' at the end of the source folders
~/Scripts
~/Documents

#################### Web files ####################
# My Sites
#Folder to backup		#Folder to which it should be backuped to
/var/www/html/Sites		Htdocs/
/var/www/html/Projects	Htdocs/

If there is just one column in a line, that folder will be backuped to “<backup folder>/<folder name>“. Let say that my backup destination folder is ‘/var/Backup/Rsync‘. So the first line, ‘~/Scripts‘ will copy the contents of ‘~/Scripts‘ to ‘/var/Backup/Rsync/Scripts‘

If a line in the configuration file has two columns, then an extra folder will be created with the name provided in the second column. For example, the line ‘/var/www/html/Sites     Htdocs/‘ will create a backup of ‘/var/www/html/Sites‘ in ‘/var/Backup/Rsync/Htdocs/Sites‘

And if you have not guessed it already, all lines that begin in a # are comments and will be ignored.

The Script

There is the perl script that automates the rsync calls…

#!/usr/bin/perl

#EDIT THIS LINE
$backup_folder = '/var/Backup/Rsync'; #Final '/' must NOT be there.

use File::Basename;
my $config_file = dirname($0) . "/rsyncbackup.config";
my @all_locations = removeComments(getFileContents($config_file));

chdir($backup_folder) or die("Cannot go to folder '$backup_folder'");

foreach my $folder_locations (@all_locations) {
	my($folder,$backup_location) = split(/\s+/,$folder_locations);

	print "Backing up $folder to $backup_location ... ";
	`rsync -a $folder $backup_folder/$backup_location`;
	print "Done\n";
}

sub getFileContents {
	my $file = shift;
	my @lines;
	if(!open (FILE,$file)) {
		die("Can't open '$file': $!");
	} else {
		@lines=<FILE>;
		close(FILE);
	}
	return @lines;
}

sub removeComments {
	my @lines = @_;

	@cleaned = grep(!/^\s*#/, @lines); #Remove Comments
	@cleaned = grep(!/^\s*$/, @cleaned); #Remove Empty lines

	return @cleaned;
}

Execute this script using the command ‘perl RsyncBackup.pl’. In my system I have created an alias ‘bk’ for this script. I recommend that you make a similar alias if you take backups regularly(extremely recommended).

Backing up is done using rsync – so its faster than a simple ‘cp’ as only the modified and new files are copied.

To me, a shell script is a script that automates repetitive tasks. But that is not the ‘official’ definition. Wikipedia has this definition…

A shell script is a script written for the shell, or command line interpreter, of an operating system.

I use a definition that defines the purpose of the script – while the others prefer a definition that defines the technology used. I am not going to claim that my definition is better than the other definition – that’s pointless. Besides, even I think that the ‘other’ definition is the right one. But I will try to show you the advantages of my approach.

The Purpose

I like to automate things(in other words, I’m lazy). So I have a nice little collection of custom shell scripts. But there is a huge barrier to writing shell scripts – the language used. Traditionally shell scripts are written in a language provided by the shell – like bash or tcsh. That is the problem – these languages are Bad – with a capital ‘B’.

The Problem

To people who are accustomed to decent languages, these shell languages will seem clunky – or even evil. But since most shell scripts are small, most people don’t mind the torture.

In bash, the control flow commands seem to be thrown in as a after thought rather than something that’s built into the language. If you don’t believe me, compare the ‘if’ loop of bash and Perl.

Bash

This code checks wether the variable ‘$value’ has the value 0 – if so it prints the message ‘No Value’

if [ $value -eq 0 ] ; then
	echo "No Value"
fi

Perl

The same code in Perl…

if($value == 0) {
	print "No Value";
}

Of course, Perl experts will go for if(!$value) or even unless($value) – but that’s not the point. See how better the code looks in Perl. Yeah, even I am surprised to hear those words – Perl is considered by many to be an ‘ugly’ language. But when compared to shell languages, Perl is a gem(sorry about the pun – couldn’t resist).

The Solution

The solution is simple – don’t use a shell language to write your shell scripts – use a high level scripting language like Perl. Or Python, Ruby, PHP, Tcl or even JavaScript.

I still use bash to write shell scripts – but if the shell script has an if condition(other than a simple argument check), I use a higher language – usually Perl.

Advantages of using a Shell Language

• Its supported in even the tinest linux distros – even in embedded systems.
• Its the method preferred by the majority – I hope this will change soon.
• Command calls look more natural in a shell language.

Advantages of using a High Level Language

• Better Code
• Easy to maintain
• Faster development
• Libraries provide a lot of functionality
• Easier to port to different platforms.

So why am I telling you all this? Two reasons…

One, the next time you are going to write a shell script, I want you to choose a high level language rather than using bash.

The second reason is that now that my series on Linux MP3 Players are over, I am going to take a small break from desktop posts and write on more ‘linuxy’ topics. And one of those topic is Shell Scripting. So in the future posts, I am going to share some of my shell scripts with you. So when I publish a Perl script and call it a shell script, I don’t want you to get confused .