[SOLVED] Bit operation in SHELL script

mackowiakp · 04-23-2017, 12:10 PM

I have unit connected to my Linux server over USB (named ARCO). When I "ask" one about state using command:

Code:

./arco

it returns 2 hex digits like "a7", bf" etc. First digit represents state of inputs and second state of outputs.
I can change output states by command like:

Code:

./arco 5

and it set outputs no 1 and 3 to "1", and outputs 2 and 4 to "0".

My question is. How can I set or clear particular output/bin without changing another in shell script, using command

Code:

./arco x

where x=0 to 15

Turbocapitalist · 04-23-2017, 12:55 PM

You could use printf to convert from binary to hexadecimal:

Code:

printf '%x\n' "$((2#101010101))"

But that overwrites everything.

If you want to keep the state of the bits, then it is just a matter of tracking the individual bits with variables:

Code:

d0=1;
d1=0;
d2=0;
d3=1;
printf '%x\n' "$((2#$d3$d2$d1$d0))";

Extend as needed.

rknichols · 04-23-2017, 01:41 PM

If the hex representation of the current output state is in variable OUT and you want to set bit 3:

Code:

./arco $((0x$OUT | 8))

To clear bit 3:

Code:

./arco $((0x$OUT & ~8))

Those are both passing the value to ./arco in decimal. If it needs to be in hex, you'll need to use the printf command to convert.

mackowiakp · 04-23-2017, 02:25 PM

Quote:

Originally Posted by rknichols

If the hex representation of the current output state is in variable OUT and you want to set bit 3:

Code:

./arco $((0x$OUT | 8))

To clear bit 3:

Code:

./arco $((0x$OUT & ~8))

Those are both passing the value to ./arco in decimal. If it needs to be in hex, you'll need to use the printf command to convert.

THX. It resolved my problem