This works in cygwin and Linux. Some of the previous solutions which write a file will cause the disk to thrash. This scipt does not have that problem:
SIG=1
SIG0=SIGSIG0=$SIG
while [ $SIG != 0 ] ; do
while [ $SIG = $SIG0 ] ; do
SIG=`ls -1 | md5sum | cut -c1-32`
sleep 10
done
SIG0=$SIG
ls -lrt | tail -n 1
done