diff --git a/.travis.yml b/.travis.yml
index 91da273..a9785d0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,5 @@
 language: shell
-dist: trusty
+dist: bionic
 
 os:
   - linux
diff --git a/deploy/vault_cli.sh b/deploy/vault_cli.sh
index 5395d87..8b85413 100644
--- a/deploy/vault_cli.sh
+++ b/deploy/vault_cli.sh
@@ -43,7 +43,7 @@ vault_cli_deploy() {
     return 1
   fi
 
-  VAULT_CMD=$(which vault)
+  VAULT_CMD=$(command -v vault)
   if [ ! $? ]; then
     _err "cannot find vault binary!"
     return 1
diff --git a/dnsapi/dns_cloudns.sh b/dnsapi/dns_cloudns.sh
index df824e8..381d17e 100755
--- a/dnsapi/dns_cloudns.sh
+++ b/dnsapi/dns_cloudns.sh
@@ -69,7 +69,7 @@ dns_cloudns_rm() {
   for i in $(echo "$response" | tr '{' "\n" | grep "$record"); do
     record_id=$(echo "$i" | tr ',' "\n" | grep -E '^"id"' | sed -re 's/^\"id\"\:\"([0-9]+)\"$/\1/g')
 
-    if [ ! -z "$record_id" ]; then
+    if [ -n "$record_id" ]; then
       _debug zone "$zone"
       _debug host "$host"
       _debug record "$record"
@@ -91,7 +91,7 @@ dns_cloudns_rm() {
 
 ####################  Private functions below ##################################
 _dns_cloudns_init_check() {
-  if [ ! -z "$CLOUDNS_INIT_CHECK_COMPLETED" ]; then
+  if [ -n "$CLOUDNS_INIT_CHECK_COMPLETED" ]; then
     return 0
   fi
 
@@ -164,7 +164,7 @@ _dns_cloudns_http_api_call() {
   _debug CLOUDNS_SUB_AUTH_ID "$CLOUDNS_SUB_AUTH_ID"
   _debug CLOUDNS_AUTH_PASSWORD "$CLOUDNS_AUTH_PASSWORD"
 
-  if [ ! -z "$CLOUDNS_SUB_AUTH_ID" ]; then
+  if [ -n "$CLOUDNS_SUB_AUTH_ID" ]; then
     auth_user="sub-auth-id=$CLOUDNS_SUB_AUTH_ID"
   else
     auth_user="auth-id=$CLOUDNS_AUTH_ID"
diff --git a/dnsapi/dns_cyon.sh b/dnsapi/dns_cyon.sh
index 8db3011..2dca90c 100644
--- a/dnsapi/dns_cyon.sh
+++ b/dnsapi/dns_cyon.sh
@@ -66,7 +66,7 @@ _cyon_load_credentials() {
   _debug "Save credentials to account.conf"
   _saveaccountconf CY_Username "${CY_Username}"
   _saveaccountconf CY_Password_B64 "$CY_Password_B64"
-  if [ ! -z "${CY_OTP_Secret}" ]; then
+  if [ -n "${CY_OTP_Secret}" ]; then
     _saveaccountconf CY_OTP_Secret "$CY_OTP_Secret"
   else
     _clearaccountconf CY_OTP_Secret
@@ -164,7 +164,7 @@ _cyon_login() {
   # todo: instead of just checking if the env variable is defined, check if we actually need to do a 2FA auth request.
 
   # 2FA authentication with OTP?
-  if [ ! -z "${CY_OTP_Secret}" ]; then
+  if [ -n "${CY_OTP_Secret}" ]; then
     _info "  - Authorising with OTP code..."
 
     if ! _exists oathtool; then
diff --git a/dnsapi/dns_dgon.sh b/dnsapi/dns_dgon.sh
index 515e87d..ac14da4 100755
--- a/dnsapi/dns_dgon.sh
+++ b/dnsapi/dns_dgon.sh
@@ -122,12 +122,12 @@ dns_dgon_rm() {
     ## check for what we are looking for: "type":"A","name":"$_sub_domain"
     record="$(echo "$domain_list" | _egrep_o "\"id\"\s*\:\s*\"*[0-9]+\"*[^}]*\"name\"\s*\:\s*\"$_sub_domain\"[^}]*\"data\"\s*\:\s*\"$txtvalue\"")"
 
-    if [ ! -z "$record" ]; then
+    if [ -n "$record" ]; then
 
       ## we found records
       rec_ids="$(echo "$record" | _egrep_o "id\"\s*\:\s*\"*[0-9]+" | _egrep_o "[0-9]+")"
       _debug rec_ids "$rec_ids"
-      if [ ! -z "$rec_ids" ]; then
+      if [ -n "$rec_ids" ]; then
         echo "$rec_ids" | while IFS= read -r rec_id; do
           ## delete the record
           ## delete URL for removing the one we dont want
@@ -218,7 +218,7 @@ _get_base_domain() {
       ## we got part of a domain back - grep it out
       found="$(echo "$domain_list" | _egrep_o "\"name\"\s*\:\s*\"$_domain\"")"
       ## check if it exists
-      if [ ! -z "$found" ]; then
+      if [ -n "$found" ]; then
         ## exists - exit loop returning the parts
         sub_point=$(_math $i - 1)
         _sub_domain=$(printf "%s" "$fulldomain" | cut -d . -f 1-"$sub_point")
diff --git a/dnsapi/dns_yandex.sh b/dnsapi/dns_yandex.sh
index 5721f99..0a2c333 100755
--- a/dnsapi/dns_yandex.sh
+++ b/dnsapi/dns_yandex.sh
@@ -25,7 +25,7 @@ dns_yandex_add() {
   _PDD_get_record_ids || return 1
   _debug "Record_ids: $record_ids"
 
-  if [ ! -z "$record_ids" ]; then
+  if [ -n "$record_ids" ]; then
     _info "All existing $subdomain records from $domain will be removed at the very end."
   fi