diff --git a/lib/dns.sh b/lib/dns.sh
index 47fcf14..a5f0956 100644
--- a/lib/dns.sh
+++ b/lib/dns.sh
@@ -9,12 +9,13 @@ if [ -z "${!DNS_KEYS[*]}" ]; then
 fi
 
 DNS_IP=${DNS_IP:-127.0.0.1}
-DIG=${DIG:-/usr/bin/dig}
-IDN2=${IDN2:-/usr/bin/idn2}
-JQ=${JQ:-/usr/bin/jq}
-NAMED_CHECKCONF=${NAMED_CHECKCONF:-/usr/bin/named-checkconf}
-NSUPDATE=${NSUPDATE:-/usr/bin/nsupdate}
-TERMINAL_WITH=${MAX_TERMINAL_WITH:-$(/usr/bin/tput cols)}
+DIG=${DIG:-$(which dig)} || exit 1
+IDN2=${IDN2:-$(which idn2)} || exit 1
+JQ=${JQ:-$(which jq)} || exit 1
+NAMED_CHECKCONF=${NAMED_CHECKCONF:-$(which named-checkconf)} || exit 1
+NSUPDATE=${NSUPDATE:-$(which nsupdate)} || exit 1
+TERMINAL_WITH=${MAX_TERMINAL_WITH:-$($(which stty) size | cut -d " " -f 2)} || exit 1
+
 
 ####################
 # global variables #