Change Gnome Background to Random Image (perl)

[rocuan]

First, I wrote a bare bones bash script to change the gnome desktop background to a random image
- http://ubuntuforums.org/showthread.php?p=10479253

Then, I realized there are dozens of bash scripts posted in the ubuntu forums just like this one
- http://ubuntuforums.org/showthread.php?t=329164

Next, rothalem & I rediscovered the drama of processing files in bash that have spaces in the name
- http://ubuntuforums.org/showthread.php?p=10496459

Finally, sflitman suggested dumping bash all together & just using perl
- http://ubuntuforums.org/showthread.php?p=10635809#post10635809

Result :
A pretty little perl script to change the gnome desktop wallpaper / background to a random image.
- If you are unfamiliar with perl : http://www.comp.leeds.ac.uk/Perl/start.html

The completed script isn't bullet proof but it will :
- accept command line arguments
- accept files & dirs with spaces in the name
- catch most errors or use the defaults.

Step 1 : Inherit the appropriate CPAN library ( from command line )
- Main Menu -> Accessories -> Terminal
sudo cpan File::RandomStep 2 : Cut-n-Paste this code into a perl script & change red line to the path_to_your_wallpaper_images


#!/usr/bin/perl -w
# rocuan & sflitman
use Cwd;
use strict;
use File::Random qw/random_file/;
use Getopt::Long; Getopt::Long::Configure( "bundling" );

# HELP
sub usage
{
print "USAGE : $0\n";
print " -d --dir <path> valid dir w jpg|jpeg|png images\n";
print " -h --help print this usage statement\n";
print " -i --image <path> image path : dir/image or local\n";
print " -r --recursive search folders recursively\n";
print " -v --verbose print selected image to stdout\n";
exit 0;
}

# DECLARE
my $depth = 0; # default is non recursive search
my $image = 0; # default is random image
my $verbose = 0; # default is quiet
my $cwd = cwd(); # current working dir
my $dir = "$ENV{HOME}/Pictures/Wallpaper";
my $gconf = "gconftool-2 -t str -s /desktop/gnome/background";
my $type = ( qr/\.(?:jpg|jpeg|png)$/i );

# FLAGS
GetOptions( 'd|dir=s' => \$dir,
'h|help' => \&usage,
'i|image=s' => \$image,
'r|recursive' => \$depth,
'v|verbose' => \$verbose ) or die &usage;

# MAIN
# if local path & dir are valid : reassign
if( -d "$cwd/$dir" ) { $dir = "$cwd/$dir"; }

# if local path & image are valid : set
if( -e "$cwd/$image" ) { &setPic( $verbose, "$cwd/$image" ); }

# if full path & image are valid : set
elsif( -e $image ) { &setPic( $verbose, $image ); }

# if directory is valid
elsif( -d $dir )
{
# if random image definition is successful : set
if( $image = random_file( -dir=>$dir, -recursive=>$depth, -check=>$type ) )
{
$dir =~ s/\/*$//; # cut trailing slash
&setPic( $verbose, "$dir/$image" );
}
else{ &usage; }
}
else{ &usage; }


# SET
# input : ( verbose true|false, image_path )
sub setPic
{
my $verbose = shift;
my $image = shift;
if( $verbose ) { print "Selected $image\n"; }
system qq{ $gconf/picture_filename "$image" };
system qq{ $gconf/picture_options zoom };
}
Remember:
- make it executable via command line -> chmod a+x yourscript.pl
- put your scripts in the right place: $HOME/bin -> http://ubuntuforums.org/showthread.php?t=368125

Default settings :
- search the /home/user/Pictures/Wallpaper directory & ignore the sub directories
- choose a random jpg|jpeg|png image
- set that image as gnome desktop background using gconftool-2

Options :
-d user defined directory with or without trailing slash
-h usage statement with appropriate flags
-i set user defined image via full path or local path
-r search folders recursively
-v print path of selected image to stdout
* empty dirs or invalid data will result in usage statement or default settings

The command line flags can be either short( -h ) or extended( --help ) or bundled together( -vrd <directory> )

Note :
The perl command GetOptions uses key=>value pairs( hashes ) to define each flag.
It can be tricky to wrap your brain around how GetOptions works.
These are decent tutorials :
- http://www.perlhowto.com/parsing_command_line_parameters_with_getopt_long
- http://www.vromans.org/johan/articles/getopt.html

Thanx to both rothalem & sflitman for keeping me interested in this

[N33k]

I was looking for something similar to this when I found it, I wondered how I might change it to only change the wallpaper when ever the screen goes off, such as when I shut down, reboot, or suspend, and maybe whenever the screensaver starts. Would it be possible to do that? If you could tell me how, I'd modify it myself, not asking you to do the work for me.

[rocuan]

Good idea! I think I can point you in the right direction.

To tie script to a hot-key / keyboard shortcut:
- System->Preferences->Keyboard Shortcuts
- click add
- give it the full path -> (ie) "perl /home/me/bin/wallswap.pl"

To run script at start up / login :
- Main Menu -> System -> Preferences -> Startup Applications
- click Add
- give it a name
- in the command box use full path to the script ( perl /home/user/bin/wallswitch.pl )

To run script at screensaver start / stop :
- You need to build another perl script to sit around and "listen" for the screensaver signal
- Follow this guide : http://superuser.com/questions/166232/running-a-program-when-screen-is-unlocked-automatically-ubuntu
- substitute the following to either the if or elsif statement ( less latency if you add to if )

system( "/usr/bin/perl path_to_your_perl_script" );
- test the script with two terminal windows & activate the gnome screensaver via command line :

gnome-screensaver-command --activate- add the listen script to start-up via: Main Menu -> System -> Preferences -> Startup Applications

To run script at wake-up :
note: I have not got this to work on my hardware ( acer aspire 5532 POS, Lucid 10.04 )
- You need to add a bash script to /etc/pm/sleep.d/
- Follow this guide : http://ubuntuforums.org/showthread.php?t=1484156
- Substitute
/etc/init.d/icecast2 restartwith
/usr/bin/perl path_to_your_perl_scriptcaution : modifying the /etc/pm/sleep.d/ folder incorrectly WILL corrupt your system.

[rocuan]

started a new thread on changing the background image at system wakeup http://ubuntuforums.org/showthread.php?p=10663041

[N33k]

Appreciate the help, and I'll be eagerly following your new thread, too.