20.4 groups: Print group names a user is in

groups prints the names of the primary and any supplementary groups for each given username, or the current process if no names are given. If names are given, the name of each user is printed before the list of that user's groups. Synopsis:

groups [username]...

The group lists are equivalent to the output of the command `id -Gn'.

The only options are `--help' and `--version'. See section 2. Common options.