To make things more complicated, fpSystem calls the shell that is registered as your systems /bin/sh, which *can* be a symlink to bash, but also to any other shell such as the Bourne Shell (sh), Z-Shell (zsh), Fish, etc.
So you cannot assume any shell specific functionality when calling system. If you need such functionality, you should be calling the respective shell directly. In this case you also do not need fpsystem but can also just rely on TProcess or RunCommand