Watch for file changes in sh

watch.sh

#!/bin/sh

FILE_TO_WATCH=$1

OLD=`sha1sum $FILE_TO_WATCH`
NEW=$OLD

while true; do

        sleep 1

        NEW=`sha1sum $FILE_TO_WATCH`

        if [ $? -ne 0 ]
        then
                OLD=0;
                continue;
        fi

        if [ "$NEW" = "$OLD" ]
        then
                continue;
        fi

        echo 'File Cambiato!'

        OLD=$NEW

done