This is a script that extracts the layers of a XCF file to individual PNG files. It uses xcftools (debian/ubuntu package):
#!/bin/bash
xcffile=$1
layers=`xcfinfo $xcffile | awk '{ print $NF }'`
destdir=`dirname $xcffile`/layers
mkdir $destdir
for layer in $layers
do
echo saving $layer to $destdir/$layer.png
xcf2png -o $destdir/$layer.png $xcffile $layer
done
exit 0