grpck - check group database entries
The grpck utility checks that a file in group(5)
does not contain any errors; it checks the /etc/group file by
default.
Too many/few fields
An entry in the group file does not have the proper
number of fields.
No group name
The group name field of an entry is empty.
Bad character(s) in group name
The group name in an entry contains characters other than
lower-case letters and digits.
Invalid GID
The group ID field in an entry is not numeric or is
greater than 65535.
Null login name
A login name in the list of login names in an entry is
null.
Logname not found in password file
A login name in the list of login names in an entry is
not in the password file.
Line too long
A line (including the newline character) in the group
file exceeds the maximum length of 512 characters.
Duplicate logname entry
A login name appears more than once in the list of login
names for a group file entry.
Out of memory
The program cannot allocate memory in order to
continue.
Maximum groups exceeded for logname
A login name's group membership exceeds the maximum,
NGROUPS_MAX.