The grpck utility checks that a file in group(4) does not contain any errors; it checks the /etc/group file by default.

/etc/group

See attributes(5) for descriptions of the following attributes:

groups(1), group(4), passwd(4), attributes(5)

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.