cntdown.sh

#!/bin/sh
#
# Copyright © 2022-2023 Chee Bin HOH. All rights reserved.
#
# A front end to cntdown
#
# Happy coding!  .... note that I am always a C programmer before
# I am anything else in computing, so the habit of declaring variable
# in the proper scope even thought bourne shell has a loose scope
# definition and variable just spawn into existence in outer scope
# if it is assigned value in inner scope. 


displayHelp()
{
  echo "Usage: `basename $0` [-H hours -M minutes -S seconds -b -s -m \"message at end\" -f \"%Y-%m-%d %H:%M:%S\"] \"2022-01-21 12:00:00\""
}


# parameters parsing
silent=""
beep=""
adjustHour=""
adjustMin=""
adjustSecond=""
while getopts "H:M:S:bm:sf:h" opt; do
  case "$opt" in
    H)
      adjustHour="${OPTARG}"
      ;;
    M)
      adjustMin="${OPTARG}"
      ;;
    S)
      adjustSecond="${OPTARG}"
      ;;
    b)
      beep="yes"
      ;;
    s)
      silent="yes"
      ;;
    f)
      formatOption="-f ${OPTARG}"
      ;;
    m)
      msg=${OPTARG}
      ;;
    *)
      displayHelp
      exit 1
  esac
done


# FIXME: put up an autoconf system to detect version of date and then
# customize the script file accordingly, the other way is to use more
# platform independent language, like python, but who need python when
# you have bourne shell.
#
# for some reason if we try to run "date" as a command inside the "if",
# like "if date -v +1H 2>dev/null; then ..." two instances of the command
# is spawned in ubuntu shell for WSL that I test, something that I do not
# quite experience before, so I change it to capture output to force shell
# to wait for the command to run and only one instance is run. I plan to
# look into that, but this is not needed if I put it into autoconf

dateResult=$(date -v +1H 2>/dev/null)

if [ "$dateResult" = "" ]; then
  linuxDate="yes"
else
  linuxDate=""
fi

adjustDateTimeParams=""
if [ "$adjustHour" != "" ]; then
  if [ "$linuxDate" = "yes" ]; then
    while [ "$adjustHour" -gt "0" ]; do
      adjustDateTimeParams="${adjustDateTimeParams} next hour"
       adjustHour=$((adjustHour -  1))
    done
  else
    adjustDateTimeParams="-v +${adjustHour}H"
  fi
fi

if [ "$adjustMin" != "" ]; then
  adjustDateTimeParams="$adjustDateTimeParams -v +${adjustMin}M"
fi

if [ "$adjustSecond" != "" ]; then
  adjustDateTimeParams="$adjustDateTimeParams -v +${adjustSecond}S"
fi

dateTimeVal=""
if [ "$adjustDateTimeParams" != ""  ]; then
  if [ "$linuxDate" = "yes" ]; then
    dateTimeVal=`date --date="$adjustDateTimeParams" +"%Y-%m-%d %H:%M:%S"`
  else
    dateTimeVal=`date $adjustDateTimeParams "+%Y-%m-%d %H:%M:%S"`
  fi
fi

shift $((OPTIND-1))

if [ "$#" -eq "1" ]; then
   dateTimeVal="$*"
fi

if [ "$dateTimeVal" = "" ]; then
  displayHelp
  exit 1
fi


# main body
remain=`./cntdown.out ${formatOption+"$formatOption"} "$dateTimeVal"`
runResult=$?

if [ "$runResult" -ne "0" ]; then
  exit $runResult
fi

while [ "${remain}" -gt "0" ]; do
  if [ "${silent}" != "yes" ]; then
    echo "\r                        \c" # a quick hack :)
    echo "\r${remain}\c";
  fi

  sleep 1;

  remain=`./cntdown.out ${formatOption+"$formatOption"} "$dateTimeVal"`
done

if [ "${remain}" -eq "0" ]; then
  if [ "${silent}" != "yes" ]; then
    echo "\r${msg:-0}"
  fi

  if [ "${beep}" == "yes" ]; then
    echo '\007\c'
  fi
fi