Bash script to display number of days till a given date.

days-till

#!/usr/bin/env bash

till_date=$(echo $1 | tr -d "-")


echo ${till_date} | egrep -q "([0-9]){8,}"

(($? != 0)) && {
  echo "Invalid date." 1>&2
  echo "Usage: days-till YYYY-MM-DD" 1>&2
  echo "Dashes are optional." 1>&2
  exit 1
}

till_timestamp=$(date -jf %Y%m%d ${till_date} +%s)
now_timestamp=$(date +%s)

days=$(expr $(expr ${till_timestamp} - ${now_timestamp}) / 86400)

echo ${days} till $(date -r ${till_timestamp} +"%a, %b %e, %Y")