The group field is the group name used for granting file access to users who are members of the group. The gid field is the number associated with the group name. They should both be unique across the system (and often across a group of systems) since they control file access. The passwd field is an optional encrypted password. This field is rarely used and an asterisk is normally placed in it rather than leaving it blank. The member field contains the names of users granted the privileges of group The member names are separated by commas without spaces or newlines. A user is automatically in a group if that group was specified in their /etc/passwd entry and does not need to be added to that group in the /etc/group file.
+name:*::
which causes the specified group to be included from the group.byname YP map.
If no group name is specified, or the ``+'' (plus sign) appears alone on line, all groups are included from the YP map.
YP references may appear anywhere in the file, but the single ``+'' form should be on the last line, for historical reasons. Only the first group with a specific name encountered, whether in the file itself, or included via YP, will be used.
YP file format first appeared in SunOS.