#!/usr/bin/env bash

tmp=$(mktemp)
while IFS= read -r line; do
    echo $line >> $tmp
done

first_line=$(head -n1 $tmp|grep "timestamp,nsecs,power") # To check for validity
last_line=$(cat $tmp | tail -n1)
ncomma=$(echo "$last_line" | tr -cd ',' | wc -c | tr -d ' ') # To check for validity

# Check if measurements are valid (not perfect test but sufficient)
if [ -z "${first_line}" ] || [ $ncomma -ne 2 ]
then
    cat $tmp
    exit 100
fi

# If valid then proceed to uniqueness
cat $tmp | awk -F"," 'BEGIN{LAST=-1;skipped=0} {if(LAST!=$3){print $1","$2","$3;skipped=0}else{skipped=1} LAST=$3} END{if(skipped){print "'$last_line'"}}'
rm $tmp