chgrp
Change group ownership (update the group ID of files.)
SYNTAX 
      chgrp [-fhv] [-R [-H | -L | -P]] group file ...
The group operand can be either a group name, or a numeric group ID.
KEY
   -R     Recurse: Change the mode of file hierarchies rooted in the files
          instead of just the files themselves.
   -R -H      Follow symbolic links on the command line
	       (by default Symbolic links within the tree are not followed.)	       
   -R -L      All symbolic links are followed.
   -R -P      No symbolic links are followed. (default)
   -f     Force, ignores errors, except for usage errors and doesn't query
	  about strange modes (unless the user lacks permissions).
   -h     If the file is a symbolic link, the group ID of the link itself
	  is changed rather than the file that is pointed to.
   -v     Verbose, show filenames as the group is modified.
 The user invoking chgrp must belong to the specified 
  group and be the owner of the file, or be the super-user.
  
Notes
The chgrp utility exits 0 on success, and >0 if an error occurs.
The -v option is non-standard and its use in scripts is not recommended.
Examples
  
  Assign Ursula as the owner of "MyFile.txt" file in the Shared directory. 
sudo chown Ursula /Users/Shared/MyFile.txt
Assign Ursula as the owner, and staff as the group for everything in the "tmp" folder
sudo chown -R Ursula:staff /Users/Shared/tmp/
 "If an organization carries the word "united" in its name, it means 
  it isn't, e. g., United Nations, United Arab Republic, United Kingdom, United 
  States" - Professor 
  Charles I. Issawi 
  
   Related commands:
  
  chflags - Change a file or folder's flags. 
  chmod - Change access permissions
 
  chown - Change file owner and group 
  install - Copy files and set attributes 
  umask - Users file creation mask
  
  Equivalent BASH command:
  
chgrp - Change file owner and/or group.