I have 2 programs, The first one change the value of gpio(I call it changer), the another one will check the gpio port's value(I call it checker), The problem is if I run this 2 program in the same time, can the checker check the value that changed by changer? Thx!
Yes, that should be fine. As long as your "checker" does not touch the state of the pins, it is fine to check the value of a pin from multiple processes. Make sure that your checker does not change the pin state, or you'll see very strange behavior.