Fix unbound variable errors

seqs/snmp.sh

@@ -73,7 +73,7 @@ step_2() {
   addConf -a "$v3AuthEntry" "$v3AuthLoc"
 
   shift
-  if [ ! -z $1 ] && [ "$1" == "-s" ] ; then
+  if [ -n "${1:-}" ] && [ "$1" == "-s" ] ; then
     info "Stop after creating authentication config"
     exe service snmpd start
     return 0
@@ -109,7 +109,7 @@ step_5_alias() { echo "ufw"; }
 step_5() {
   shift
   local lInterface="eth0"
-  [ ! -z "$1" ] && lInterface="$1"
+  [ -n "${1:-}" ] && lInterface="$1"
   # Check if interface exists
   ip -br a | grep -E "^$lInterface" >>/dev/null 2>&1
   endReturn -o $? "Interface $lInterface does not exist"