whendoesthisexpire.sh

#!/bin/sh

cert_expiry(){
    # cert_expiry host port
    openssl s_client -connect "${1}:${2}" -servername "${1}" 2>/dev/null </dev/null | \
	openssl x509 -noout -dates | grep notAfter | cut -d= -f 2
}

difference(){
    # difference date date
    echo $(( $(date -d "$1" +%s ) - $(date -d "$2" +%s) ))
}

format(){
    # format seconds
    seconds="$1"
    seconds_in_day=86400
    seconds_in_hour=3600
    seconds_in_minute=60
    output=""
    while [ "$seconds" -gt "0" ]; do
	if [ "$seconds" -ge "$seconds_in_day" ]; then
	    days="$(( seconds / seconds_in_day ))"
	    output="${days} days; "
	    seconds="$(( seconds - seconds_in_day * days ))"
	elif [ "$seconds" -ge "$seconds_in_hour" ]; then
            hours="$(( seconds / seconds_in_hour ))"
            output="${output}${hours} hours; "
            seconds="$(( seconds - seconds_in_hour * hours ))"
	elif [ "$seconds" -ge "$seconds_in_minute" ]; then
	    minutes="$(( seconds / seconds_in_minute ))"
            output="${output}$minutes minutes; "
	    seconds="$(( seconds - seconds_in_minute * minutes))"
	else
	    output="${output}$seconds seconds;"
	    seconds=0
	fi
    done
    echo "$output"
}

check_cert(){
    # check_cert host port
    expiry="$(cert_expiry $1 $2)"
    echo "$expiry"
    format $(difference "$expiry" "now")
}

check_cert "$1" "$2"