bash script to check ssl certificate expiration

sslcheck.sh

#!/bin/bash

hosts=$@
date_cmd=""

if [[ "$OSTYPE" == "darwin"* ]]; then
  # make sure you have 'coreutils' -- brew install coreutils
  date_cmd="gdate"
else
  date_cmd="date"
fi

time_now=`$date_cmd +%s`

for host in "${hosts[@]}"
do
  expire_date=`curl -k -v https://$host/ 2>&1 > /dev/null | grep "expire date:" | cut -d ":" -f 2-`
  expire_date=$(sed -e 's/[[:space:]]*$//' <<<${expire_date})

  time_host=$( $date_cmd -d "$expire_date" +%s )
  expiry_days="$(( ($time_host - $time_now) / (3600 * 24) ))"

  echo "$host - $expire_date - (Expired in $expiry_days days)."
done