count log lines per second

count.sh

cat log/chupacabra.log | grep -o -E "[0-9]{2}:[0-9]{2}:[0-9]{2}" | uniq -c

# matches the whole date at the begining of the line
tail -n 100 log/chupacabra.log | grep -o -E "^[0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2}" | uniq -c

To grab only the counts
cat counts_and_times_file | grep -o -E "^\s*(\d*)\s{1}"