#!/bin/bash
export LC_ALL=en_US.UTF-8
FILE="/mnt/data/temp/timelog.csv"
CMD="curl -s -m 60 --output /dev/null https://f-droid.org/assets/favicon-16x16.png --resolve f-droid.org:443:5.9.48.82"

HDR=$(cat << HDR
"# ${CMD}"
"# Timestamp is MsExcel compatible, just format cell as date/time"
"Timestamp","Time(s)","Error"
HDR
)

echo "$HDR" > "${FILE}"
TIMEFORMAT=%R
while sleep 60
do
    # Exit script when FILE is deleted, moved or renamed.
    [ -e "${FILE}" ] || break
    D=$(echo "($(date +%s%z*36)) / 86400 + 25569 " | bc -l)
    T=$( (time ${CMD}|tail -n1) 2>&1 )
    echo "$D,$T,$?" >> $FILE
done