Question

I run the following in the command line:

prog1 | prog2

The output (say, X) of above is a 4-digit hex number, e.g. FA34.
prog1 is a java program which reads data every 100ms on the serial. prog2 is the cut command which cuts out a portion I need. This works fine and I can see the desired value every 100ms on the standard out.

What I want:

prog1 | prog2 | <convert X to decimal> | <multiply by 2>

How to do this, using pipes or not, in the command line in one-go?

Note: I wrote a bash script to convert X to decimal and multiply by 2. But I couldn’t direct X into my script as an argument.

Answer 1

Here’s a funny possibility:

{ echo "iscale=16"; prog1 | prog2; } | sed 's/$/*2/' | bc

This echos iscale=16 first (to tell bc to consider user’s input in radix 16). Then sed appends *2 to each line and all this goes through bc for the conversion to decimal and multiplication by 2.

There’s a limitation: your program prog2 must output all the hexadecimal numbers in upper case (e.g., FA34 not fa34). If this is a limitation, use:

{ echo "iscale=16"; prog1 | prog2; } | sed 's/\(.*\)/\U\1*2/g' | bc

instead.