Bash SSL Certificate Expiration Check

check-certs.sh

#!/bin/bash
TARGET="mysite.example.net"; 
RECIPIENT="[email protected]";
DAYS=7;
echo "checking if $TARGET expires in less than $DAYS days";
expirationdate=$(date -d "$(: | openssl s_client -connect $TARGET:443 -servername $TARGET 2>/dev/null \
                              | openssl x509 -text \
                              | grep 'Not After' \
                              |awk '{print $4,$5,$7}')" '+%s'); 
in7days=$(($(date +%s) + (86400*$DAYS)));
if [ $in7days -gt $expirationdate ]; then
    echo "KO - Certificate for $TARGET expires in less than $DAYS days, on $(date -d @$expirationdate '+%Y-%m-%d')" \
    | mail -s "Certificate expiration warning for $TARGET" $RECIPIENT ;
else
    echo "OK - Certificate expires on $expirationdate";
fi;

• First of, day-month-year. (it used to be year-month-day, yuck)

You said year-month-day, yuck, it has to be the most dumbest thing thing in this script. Year-month-day is the standard in programming.

• First of, day-month-year. (it used to be year-month-day, yuck)

You said year-month-day, yuck, it has to be the most dumbest thing thing in this script. Year-month-day is the standard in programming.

Lol 😆 then you change it to what you like.
There's a couple reasons why i made that change.

1. We - western people - read from left to right. The most important part of the date in this context is the day and potentially the month. Having that readable from left to right makes a lot of sense (to me!).
2. Same geographic argument, different reason. dd-mm-yyyy is the standard here, i'm used to that and can't stand the many differences.

As an aside, if year-month-day is a standard (didn't know that and I've been a programmer for decades by now), then i'll happily ignore that. I'll quote you for my reason: "it has to be the most dumbest thing" 😉

Working great, thanks very much for the script!