How to read a counter from a linux C program to a bash test script?

I have a large C/C++ program on a Suse linux system. We do automated testing of it with a bash script, which sends input to the program, and reads the output. It's mainly "black-box" testing, but some tests need to know a few internal details to determine if a test has passed.I have a large C/C++ program on a Suse linux sy