contains for each group the
a comma separated list of all users allowed in the group
Each group is separated from the next by a new-line.
If the password field is null, no password is demanded.
This file resides in directory /etc.
passwords, it can and does have general read
permission and can be used, for example,
to map numerical group ID's to names.
newgrp(1), crypt(3), passwd(1), passwd(5)