If only an owner (a user name or numeric user id) is given, that user is made the owner of each given file, and the files' group is not changed.
If a colon but no group name follows owner, that user is made the owner of the files and the group of the files is changed to owner's login group.
You may use `.' in place of the `:' separator. This is a GNU extension for compatibility with older scripts. New scripts should avoid the use of `.' because GNU chown may fail if owner contains `.' characters.
Do not act on symbolic links themselves but rather on what they point to.
Act on symbolic links themselves instead of what they point to. This is the default. This mode relies on the lchown system call. On systems that do not provide the lchown system call, chown fails when a file specified on the command line is a symbolic link. By default, no diagnostic is issued for symbolic links encountered during a recursive traversal, but see `--verbose'.
Output a diagnostic for every file processed. If a symbolic link is encountered during a recursive traversal on a system without the lchown system call, and `--no-dereference' is in effect, then issue a diagnostic saying neither the symbolic link nor its referent is being changed.