1.console can print when machine suspend
	echo 10 > /proc/sys/kernel/printk
	echo N > /sys/module/printk/parameters/console_suspend_enabled

2.call machine to sleep
	echo mem > /sys/power/state
	or
	echo standby > /sys/power/state

3.input key at console
	input keyevent 7 #for key '0',you can find define of number at frameworks/base/native/include/android/keycodes.h
	input text "Android" #input string char

4.logcat how to use
	if you just want to show message like:D/InputReaderHover( 2144): Input event: device=0x10001 type=0x1 scancode=102 keycode=3 value=0
	logcat -s "InputReaderHover:D"

5.debug wake_lock
	echo 0x1f > /sys/module/wakelock/parameters/debug_mask

6.make android quickly
	make -j16 > info 2>&1&
	gf

7.repo rest tags
	repo forall -p -c git reset --hard android-4.0.4_r2.1