Interleave two different datapoint count csv files to fill all minutes of a day

all-minutes.sh

for h in {0..23} 
do 
    for m in {0..59}
    do 
        # .csv format:
        # 00:07,2
        # 00:10,17
        # this combines single.csv and all csv to so that all minutes of the day are counted
        # all.csv includes single.csv numbers, but we want em separate
        ts=`printf "%02d:%02d" $h $m`
        a=`fgrep $ts single.csv | cut -d',' -f2`
        b=`fgrep $ts all.csv | cut -d',' -f2`
        if [ -z $a ] ; then
            if [ -z $b ] ; then
                echo "$ts,0,0"
            else
                echo "$ts,0,$b"
            fi
        else
            echo "$ts,$a,$b"
        fi
    done
done