fix/check empty --fmask

1 files changed, 5 insertions, 0 deletions

diff --git a/sub_client_output.c b/sub_client_output.c
index 0c4951e..8d6034a 100644
--- a/sub_client_output.c
+++ b/sub_client_output.c
@@ -629,6 +629,11 @@ void print_message_file(struct mosq_config *cfg, const struct mosquitto_message
 	if(cfg->format && strlen(cfg->fmask) == 0) {
 		_fmask(cfg->format, cfg, message); /* experimental */
 	} else {
+		if(strlen(cfg->fmask) == 0) {
+			fprintf(stderr, "Error: fmask is empty, try an absolute path string.\n");
+			fflush(stdout);
+			return;
+        }
 		_fmask(cfg->fmask, cfg, message);
 	}