GROUP(5) File Formats Manual GROUP(5)
group - group file
Group contains for each group the following information:
numerical group ID
a comma separated list of all users allowed in the group
This is an ASCII file. The fields are separated by colons; 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. Because of the encrypted pass-
words, 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)