Unclean shutdown is not recommended for Linux OS. I don't know the distro u r using at the moment.... there's a better way to detect a graceful shutdown. If you add this line: touch /etc/fastboot to the /etc/rc.d/rc.local_shutdown script, every time u shutdown the comp right after that a file is created & on next reboot, Linux boots scripts search for it and if found, fsck checks are skipped and that file is removed.

May be /etc/rc.d location changed for various distro.