bind -a '#r' /dev 
 /dev/switch 

The switch device serves a one-level directory, giving access to one read-only file, switch . A read returns the value of the development board's option switch (DS1), represented as a decimal number from 0 to 15, representing four bits, each corresponding to one of the four toggles. Each toggle produces the value 0 when it is set `ON' and 1 when it is off. Toggle 1 corresponds to bit 1<<3 in the number, toggle 2 corresponds to bit 1<<2 , and so on