From 7b77c9fa5cd2d6903ec74de3524c4e18cf3aebf0 Mon Sep 17 00:00:00 2001
From: StackKorora <42156355+StackKorora@users.noreply.github.com>
Date: Mon, 14 Sep 2020 21:06:05 -0500
Subject: [PATCH] whois_expire.sh update

Started with just adding a bit to check for whois since one of my deployments failed when it wasn't installed. Then I yanked the extra head command to simplify with awk. Then decided to simplify the dates...Finally decided to run it through ShellCheck just to verify my code... :-)
---
 externalscripts/whois_expire.sh | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/externalscripts/whois_expire.sh b/externalscripts/whois_expire.sh
index 4e2e08d..f17f33b 100644
--- a/externalscripts/whois_expire.sh
+++ b/externalscripts/whois_expire.sh
@@ -1,22 +1,28 @@
 #!/bin/bash
 
+# Check to ensure argument has been passed.
 if [ $# -ne 1 ]; then
         echo "usage: $0 domain_name"
         exit 1
 fi
 
-domain=$1
-
-expiration_string=`whois "$domain" 2>&1 |  egrep -i 'Expiration|Expires on|Expiry date|paid-till' | head -1  | awk '{print $NF}'`
-if [ $? -ne 0 ]; then
-        echo "ERROR executing whois for the $domain domain - $expiration_string"
-        exit 1
+# Check to ensure whois is functional.
+if ! type -tP whois &> /dev/null
+then
+        echo "Please install whois."
+        exit 2
 fi
 
-expiration_epoch=`date --date="$expiration_string" '+%s'`
-rightnow_epoch=`date '+%s'`
+domain=$1
 
-seconds_left=`expr $expiration_epoch - $rightnow_epoch`
-days_left=`expr $seconds_left / 86400`
+# Check whois for the domain, filter out expire date, then awk filters the last field of the first line
+if expiration_string=$(whois "$domain" 2>&1 | grep -Ei 'Expiration|Expires on|Expiry date|paid-till' | awk 'NR==1{print $NF}'); then
+        expiration_epoch=$(date --date="$expiration_string" '+%s')
+        rightnow_epoch=$(date '+%s')
 
-echo $days_left
+        # Bash does lookups on arithmetic variables; no $ required.
+        echo "$(( (expiration_epoch - rightnow_epoch) / 86400 ))"
+else
+        echo "ERROR executing whois for the $domain domain - $expiration_string"
+        exit 3
+fi