I use astyle as a tool to enforce coding style standards. One area that causes me a bit of pain is that there does not appear to be a way to have astyle tell you that it would have re-formatted the file buy not actually re-format the file.
Right now I work around this by either:
copying the file into a temp location running astyle on the copy and then comparing that back to the original
setting the --formatted option and then grepping the output of astyle for 'ormatted'
Depending on how I'm checking.
What would be very useful would be --dry-run option with the return code of astyle indicating if it would have re-formatted the file.