Use awk to replace grep and sed command

.gitlab-ci.yml

@@ -385,8 +385,8 @@ cleanup:
     - build
   script:
     - |
-      SERVER_TO_BE_DELETE=($(openstack server list --name $OOD_INSTANCE_NAME --sort-column Image --sort-descending -f value -c ID | sed -n $(($NUM_SERVER_TO_KEEP+1))',$p'))
-      IMAGE_TO_BE_DELETE=($(openstack image list --sort-column Name --sort-descending -f value -c Name -c ID | grep -P ' ood-\d{8}$' | sed -n $(($NUM_IMAGE_TO_KEEP+1))',$p' | awk '{print $1}'))
+      SERVER_TO_BE_DELETE=($(openstack server list --name $OOD_INSTANCE_NAME --sort-column Image --sort-descending -f value -c ID | awk -v NSTK=$NUM_SERVER_TO_KEEP '{count++} {if (count>NSTK) print}'))
+      IMAGE_TO_BE_DELETE=($(openstack image list --sort-column Name --sort-descending -f value -c Name -c ID | awk -v NITK=$NUM_IMAGE_TO_KEEP '/ ood-[[:digit:]]{8}$/ {count++} {if (count>NITK) print $1}'))
       for svr in ${SERVER_TO_BE_DELETE[@]}; do
         openstack server delete ${svr}
       done