local maximums

#!/bin/bash
out='out.txt'
# truncate
: >${out}
x1=0
y1=0
x2=0
y2=0
while read -r x y; do
  if (( $(echo "${y1}<${y2}" | bc -l) &&
        $(echo "${y2}>${y}" | bc -l) )) ; then
    echo "${x2} ${y2}" >>${out}
  fi
  x1=${x2}
  y1=${y2}
  x2=${x}
  y2=${y}
done