new: adding function ``get_running_containers_for_service``.

bin/compose

@@ -681,6 +681,13 @@ EOF
 export -f docker_add_host_declaration
 
 
+get_running_containers_for_service() {
+    local service="$1"
+
+    docker ps --filter label="compose.service=$service" --format="{{.ID}}"
+}
+export -f get_running_containers_for_service
+
 
 ##
 ## Internal Process