Check list of domains and output text file with certificate expiry dates

certificate-expiry.sh

#!/bin/bash

input="domains.txt" #text file with each domain on a new line
output="expiry.txt" #where the result should be written to

echo -n "" > $output

while read line; do
	domain=$line	
	dates=$(echo | openssl s_client -servername $domain -connect $domain:443 2>/dev/null | openssl x509 -noout -dates)

	not_after=$(echo $dates|cut -d '=' -f 3 | tr -dc '[:alnum:]:[:space:]')
	#echo  $not_after
	
	IFS=', ' read -r -a array <<< "$not_after"
	expiry=$(date -jf "%Y %b %d %T %Z" "${array[3]} ${array[0]} ${array[1]} ${array[2]} ${array[4]}" +"%Y-%b-%d") #Feb 23 12:00:00 2020 GMT
	#echo $expiry

	echo "$expiry | $domain" >> $output

done < $input

sort -o $output -n -t"-" -k1n -k2M -k3n $output