I have a LaTeX file that executes an external shell command to get some information; this works on my local machine but fails on Overleaf. That's okay, not a big deal—if I can wrap the code in an if-then conditional that checks if it's executing on Overleaf.
Problem: how can I make my LaTeX code check if being run on Overleaf?
Clarification added 2017-07-31: I already know how to test for shell escapes, and conditionalize my code appropriately. The problem is not whether shell escapes work; the problem is really about testing for Overleaf versus other environments.