unix:shell:find parent directory

PRG="$0"

while [ -h "$PRG" ]; do
ls=`ls -ld "$PRG"`
link=`expr "$ls" : '.*-> \(.*\)$'`
echo "link:$link"
if expr "$link" : '.*/.*' > /dev/null; then
PRG="$link"
else
PRG=`dirname "$PRG"`/"$link"
fi
done

# Get standard environment variables
PRGDIR=`dirname "$PRG"`