I'm glad you identified the problem. I was just assuming that one of your programs read data from the input stream, but it seems that you were trying to use the input stream to pass parameters to the shell script.
Here's a simple example of how you would pass a KM variable to a shell script as a parameter to the script:
The shell file contains this:
When you run those KM actions, you will get the word "Hello," displayed, as that corresponds to $1.