diff --git a/ch04/host_monitor_notification.sh b/ch04/host_monitor_notification.sh
index cc933a4..3f7c2b3 100644
--- a/ch04/host_monitor_notification.sh
+++ b/ch04/host_monitor_notification.sh
@@ -10,7 +10,7 @@ TO_ADDR="security@blackhatbash.com"
 while true; do 
   echo "Performing an ARP scan against ${NETWORK}..."
   sudo arp-scan -x -I ${INTERFACE} ${NETWORK} | while read -r line; do
-    host="$(echo "${line}" | awk '{print $1}')"
+    host=$(echo "${line}" | awk '{print $1}')
     if ! grep -q "${host}" "${KNOWN_HOSTS}"; then
       echo "Found a new host: ${host}!"
       echo "${host}" >> "${KNOWN_HOSTS}"
diff --git a/ch04/port_watchdog.sh b/ch04/port_watchdog.sh
index 580ba96..bebe9f1 100644
--- a/ch04/port_watchdog.sh
+++ b/ch04/port_watchdog.sh
@@ -1,7 +1,7 @@
 #!/bin/bash 
 LOG_FILE="watchdog.log"
-IP_ADDRESS="$1"
-WATCHED_PORT="$2"
+IP_ADDRESS="${1}"
+WATCHED_PORT="${2}"
 
 service_discovery(){
   local host