写了一个脚本，生成gnome桌面背景slide模式所需的xml文件

#!/bin/bash
printusage(){
echo "Usage: $0 [-s static duration] [-t transfer duration] [-o output file] directory "
echo "	 $0 -h"
echo "	    -s: static duration, default 1600"
echo "	    -t: transfer durtaion, default 5"
echo "	    -o:	output file, default stdout"
echo "	    -h: display this info"
echo "	    directory: the directory that contains the images"
}
# get options
# -t transfer duration
# -s static durtaion
# -o output xml file, default stdout
STATIC_DUR=1600.0
TRANS_DUR=5.0
OUT_XML=
while getopts t:s:o:h opt ; do
case "$opt"
in
t)  TRANS_DUR=$OPTARG;;
s)  STATIC_DUR=$OPTARG;;
o)  OUT_XML=$OPTARG
if [ -e $OUT_XML ] ; then
echo "NOTICE: $2 exists in current directory."
echo -n "Do you want to overwrite it? [y/n] "
read ans
case "$ans" in
y | yes | Yes | YES | Y ) ;;
*)	echo "exit for existed output file"
exit 2;;
esac
fi
;;
h)  printusage
exit 1;;
/?) echo "Usage: $0 [-s static duration] [-t transfer duration] [-o output file] directory "
echo "use /"$0 -h/" for more details"
exit 1;;
esac
done
# shift the options away
shift $(( OPTIND - 1))
# get main dir
MAIN_DIR=
if [ $# -ne 1 ] ; then
echo "agrument /"directory/" needed!"
printusage
exit 1
elif [ ! -d $1 ] ; then
echo "$1 is NOT a directory"
printusage
exit 1
else
MAIN_DIR=$1
if [ $MAIN_DIR = "." ]; then
MAIN_DIR=$(pwd)
fi
MAIN_DIR=${MAIN_DIR%/}
fi

# search image files
FILELIST=
echo "Searching image files in $MAIN_DIR :"
for f in $( echo $MAIN_DIR/*); do
if ( file $f | grep -q "JPEG" ) || ( file $f | grep -q "PNG") ; then
echo $f
FILELIST="$FILELIST $f"
else
echo "WARNING! file $f is not a image file, ignore it"
fi
done

# ack by user
echo
echo -n "Is these files OK? [y/n] "
read ans
case "$ans" in
y | Y | yes | Yes | YES ) ;;
*) exit 3;;
esac
# function create_xml, to create xml script
create_xml() {
FIRST=$1
# the header
echo "<background>"
echo "	<starttime>"
echo "	    <year>2010</year>"
echo "	    <month>08</month>"
echo "	    <day>01</day>"
echo "	    <hour>00</hour>"
echo "	    <minute>00</minute>"
echo "	    <second>00</second>"
echo "	</starttime>"
echo
# the main body
until [ $# -le 1 ]; do
echo "  <static>"
echo "	<duration>$STATIC_DUR</duration>"
echo "	<file>$1</file>"
echo "  </static>"
echo "  <transition>"
echo "	<duration>$TRANS_DUR</duration>"
echo "	<from>$1</from>"
shift
echo "	<to>$1</to>"
echo "  </transition>"
done;
echo "  <static>"
echo "	<duration>$STATIC_DUR</duration>"
echo "	<file>$1</file>"
echo "  </static>"
echo "  <transition>"
echo "	<duration>$TRANS_DUR</duration>"
echo "	<from>$1</from>"
shift
echo "	<to>$FIRST</to>"
echo "  </transition>"
echo
# the end
echo "</background>"
}
if [ -z "$OUT_XML" ]; then
echo "dump the xml script on the screen:"
echo
create_xml $FILELIST
else
echo "create xml script file $OUT_XML."
create_xml $FILELIST > $OUT_XML
fi
exit