Fix mosquitto_sub pipe close detection.

If sending mosquitto_sub output to a pipe, mosquitto_sub will now detect
that the pipe has closed and disconnect.

Closes #2164. Thanks to Frantisek Fuka.

ChangeLog.txt

@@ -1,3 +1,11 @@
+2.0.11 - 2021-xx-xx
+===================
+
+Clients:
+- If sending mosquitto_sub output to a pipe, mosquitto_sub will now detect
+  that the pipe has closed and disconnect. Closes #2164.
+
+
 2.0.10 - 2021-04-03
 ==================
 

client/sub_client.c

@@ -96,6 +96,9 @@ static void my_message_callback(struct mosquitto *mosq, void *obj, const struct
 	}
 
 	print_message(&cfg, message, properties);
+	if(ferror(stdout)){
+		mosquitto_disconnect_v5(mosq, 0, cfg.disconnect_props);
+	}
 
 	if(cfg.msg_count>0){
 		msg_count++;