chgrp is as specified in the Single UNIX Specification but with differences as listed below.
The behaviors specified in this section are expected to disappear from a future version of the LSB; applications should only use the non-LSB-deprecated behaviors.
is like verbose, but reports only when a change is made.
affects the referent of each symbolic link, rather than the symbolic link itself.
affects symbolic links instead of any referenced file. (Available only on systems that can change the ownership of a symlink.)
suppresses most error messages.
uses RFILE's group rather than the specified GROUP value.
outputs a diagnostic for every file processed.
outputs version information and exit.