> + ret = dprintf(event_control, "%d %d %s", efd, cfd, argv[2]); I found it won't return negative value for invalid input, though errno is set properly. try: # ./cgroup_event_listner /cgroup/cgroup.procs abc while strace shows write() does return -1: # strace ./cgroup_event_listner /cgroup/cgroup.procs abc ... write(6, "7 5 abc"..., 7) = -1 EINVAL (Invalid argument) > + if (ret == -1) { > + perror("Cannot write to cgroup.event_control"); > + goto out; > + } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>