Thread: changing images for desktop background script

Hi all good people,

the other day I was visiting my girl friend who gave me a load of great images of her and me, and I thought: "Wow, these images are great! It would be nice to have them all changing on my desktop background." And so the following script was born:

Code:

#!/bin/bash
desk(){
    dir=$1
    echo "dir=$dir"

    #create 'background-1.xml' file
    namef=background-1
    extf=xml
    echo "" > $dir$namef.$extf
    
    echo "<background>
        <starttime>
            <year>2012</year>
            <month>02</month>
            <day>21</day>
            <hour>10</hour>
            <minute>05</minute>
            <second>00</second>
        </starttime>" >> $dir$namef.$extf

    #remove tmp
    cd $dir; rm tmp.txt

    #list of files in source directory   
    ls $dir > tmp.txt

    #total number of files in source directory
    number=$(ls $dir | wc -l)

    for (( i = 1; i <= $(expr $number - 1); i++ ))
    do
        current=$(head -n $i tmp.txt | tail -n 1)
        next=$(head -n $(expr $i + 1) tmp.txt | tail -n 1)
        first=$(head -n 1 tmp.txt | tail -n 1)
        final=$(head -n $number tmp.txt | tail -n 1)
        IFS=.
        read -r name extension <<< "$current"
        read -r next_n next_e <<< "$next"
        read -r first_n first_e <<< "$first"
        read -r final_n final_e <<< "$final"
        
        #check if current file is .JPG image
        echo "$extension" | grep -s 'JPG'
        if [ $? -eq 0 ] ;
        then            
            #add following text in deskfile        
            echo "<static>
                <duration>300.0</duration>
                <file>$dir$name.$extension</file>
            </static>
            <transition>
                <duration>1.0</duration>
                <from>$dir$name.$extension</from>
                <to>$dir$next_n.$next_e</to>
            </transition>" >> $dir$namef.$extf
        else
            echo "$name.$extension is not an image file"
        fi
    done
    echo "<static>
            <duration>300.0</duration>
        <file>$dir$final_n.$final_e</file>
    </static>
    <transition>
        <duration>1.0</duration>
        <from>$dir$final_n.$final_e</from>
        <to>$dir$first_n.$first_e</to>
    </transition>" >> $dir$namef.$extf
    echo "</background>" >> $dir$namef.$extf

    cd ~
}

Input to this script is a folder filled with images that you want to be changing on your background. Output of this script is a simple xml file which is then used to activate desktop images to change as a background. I use Ubuntu Maverick. I want to modify this code to be shorter and more efficient and I want to shuffle the images.

1. Is there more intelligent way of going through files other then my head-tail approach?

2. How do I make the images to shuffle?

3. Obviously I don't want to 4.JPG to be next image after each image. How do I make next image i+1 in all but last image, which points to the first one?

4. Do I need <transition> part if I don't need any transitions?

5. How do I fit images to screen?

This script works file even though there is next image 4.JPG in all of them. I don't know how. Please help me make this script better.

Best regards brothers and sisters
Storm

Edit: I just noticed that instead of /usr/share/backgrounds/ you can use any directory to store your background images, so I changed that part. Still I get images that are cropped to my screen and I would like them to fit screen. Added 5th issue.