Check and Calculate the remaining valid days of the domain, using whois command.

check_domain.sh

#!/bin/bash

########################################
# Name: Kazuhiro MUSASHI
#
# about:
#
# Usage:
#
# Author:
# Date:
########################################

set -e

# Constants
WHOIS='/usr/bin/whois'

# Check the number of the arguments
if [ $# -ne 1 ]; then
  exit 1
fi

DOMAIN=$1

# Check the specified domain name
if [ ! ${DOMAIN##*.} == "com" ]; then

  echo "Specify the .com domain name."
  exit 1

fi

# Check whether the whois command exists or not
if [ ! -x ${WHOIS} ]; then

  echo "${WHOIS} command does not exist."
  exit 1

fi

# Execute the whois command
EXPIRE=`${WHOIS} ${DOMAIN} | grep Expiration | tail -n 1 | cut -f 3 -d " "`

# Convert the expiration date into seconds
EXPIRE_SECS=`date +%s --date=${EXPIRE}`

# Acquire the now seconds
CURRENTDATE_SEC=`date +%s`

# Calculate the remaining days
((DIFF_SEC=EXPIRE_SECS-CURRENTDATE_SEC))

REMAIN_DAYS=$((DIFF_SEC/86400))

echo ${REMAIN_DAYS}

exit 0