Generate cron job lines from sunrise and sunset time provided by api.sunrise-sunset.org

dusk2dawn.sh

#!/bin/sh
#
# Set cron jobs by sunset and sunrise
# 2023, Paul Philippov <paul@themactep.com>
#
# Do not forget to tip the API provider!
# https://www.buymeacoffee.com/sunrisesunsetapi
#

# Geographic coordinates of your place
lat="42.511398"
lng="14.145070"

crontab_file="/etc/crontabs/root"
at_sunrise_marker="# at sunrise (autogenerated)"
at_sunset_marker="# at sunset (autogenerated)"

# retrieve and parse sunset and sunrise time
json=$(curl --silent --url "https://api.sunrise-sunset.org/json?lat=${lat}&lng=${lng}&formatted=0")
sunrise_hour=$(jsonfilter -s "$json" -e @.results.sunrise | awk -F[T:] '{print $2}')
sunrise_minute=$(jsonfilter -s "$json" -e @.results.sunrise | awk -F[T:] '{print $3}')
sunset_hour=$(jsonfilter -s "$json" -e @.results.sunset | awk -F[T:] '{print $2}')
sunset_minute=$(jsonfilter -s "$json" -e @.results.sunset | awk -F[T:] '{print $3}')

# create a working copy of crontab in ram
tmp_crontab_file=$(mktemp)
cp "$crontab_file" "$tmp_crontab_file"

# delete old jobs
sed -i "/$at_sunrise_marker/,+1d" "$tmp_crontab_file"
sed -i "/$at_sunset_marker/,+1d" "$tmp_crontab_file"
# create new marked jobs
{
	echo "$at_sunset_marker"
	printf "%02d %02d * * * daynight night\n" "$sunset_minute" "$sunset_hour"
	echo "$at_sunrise_marker"
	printf "%02d %02d * * * daynight day\n" "$sunrise_minute" "$sunrise_hour"
} >>"$tmp_crontab_file"

# replace actual crontab file with the updated one
cp "$tmp_crontab_file" "$crontab_file"

echo "Done"
exit 0