root@bt:~/test# chgrp --helpUsage: chgrp [OPTION]... GROUP FILE... or: chgrp [OPTION]... --reference=RFILE FILE...Change the group of each FILE to GROUP.With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect each symbolic link instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat `/' specially (the default) --preserve-root fail to operate recursively on `/' -f, --silent, --quiet suppress most error messages --reference=RFILE use RFILE's group rather than specifying a GROUP value -R, --recursive operate on files and directories recursively -v, --verbose output a diagnostic for every file processedThe following options modify how a hierarchy is traversed when the -Roption is also specified. If more than one is specified, only the finalone takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exitExamples: chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff".