A shell script to test whether the current time is between two given times

is_between.sh

#!/usr/bin/env sh

# A script that receives start and end parameters in the format HH:mm and
# exit with an error code if the current time is not within the desired
# window.
# The given times are not inclusive, so if you want 06:00-10:00 inclusive
# you need to specify 05:59 and 10:01 respectively.
# This script assumes that we are interested in time periods shorter than
# a single day, and it handles overnight periods.
# Inspired by https://unix.stackexchange.com/a/395936/305967

# eg.
# $ ./in_between.sh 10:15 11:45
# $ ./in_between.sh 21:00 06:30

current_time=$(date +%H:%M)
start_time="$1"
end_time="$2"

echo "Checking current_time ${current_time} is between ${start_time} and ${end_time}..."

is_between=false
if [ "$end_time" \> "$start_time" ]; then
  if [ "$current_time" \> "$start_time" ] && [ "$current_time" \< "$end_time" ]; then
    is_between=true
  fi
else
  if [ "$current_time" \> "$start_time" ] || [ "$current_time" \< "$end_time" ]; then
    is_between=true
  fi
fi

if [ $is_between = true ]; then
  echo "$current_time is between $start_time and $end_time"
else
  echo "$current_time is not between $start_time and $end_time"
  exit 1
fi