There is many SD sockets have separated mechanical switch to indicate SD card is inserted or not. I have one push-push micro SD socket which indicate card is present when opened and closed when it does not.
What would be proper circuit configuration in terms of power saving for Arduino to detect SD card is present with this kind of sockets?
You could use the switch to generate an interrupt to wake up a sleeping arduino, or you could poll it in software.
Possibly use it as a power switch depending on current , probably you would need a mosfet switch.
For any SPST switch you should connect one terminal to a digital INPUT pin, and the other to ground.
To poll the switch:
pinMode (pin, INPUT_PULLUP) ;
switch_state = digitalRead (pin) ;
pinMode (pin, INPUT) ;
Thus any pull up current only flows when you read the thing, not all the time.
With a momentary action button switch the normal state is open circuit so it doesn't matter
normally, but with a two-position switch you don't want the idle power consumption to depend on
the switch position.