Revert "Merge pull request #2530 from qingliangcn/master"

This reverts commit 42875c0b72863aa3f263ad227ffc7c454c001ae6, reversing
changes made to be320880b2231c6933a87fea335612cafbfeea7f.
Updating System.cmd return types
Merge pull request #2531 from jwarwick/system_cmd_type

Updating System.cmd return types