These functions operate on the netgroup database file /etc/netgroup which is described in netgroup(5). The database defines a set of netgroups, each made up of one or more triples:
(host, user, domain)
that defines a combination of host, user and domain. Any of the three fields may be specified as wildcards that match any string.
The function getnetgrent sets the three pointer arguments to the strings of the next member of the current netgroup. If any of the string pointers are (char *)0 that field is considered a wildcard.
The functions setnetgrent and endnetgrent set the current netgroup and terminate the current netgroup respectively. If setnetgrent is called with a different netgroup than the previous call, an implicit endnetgrent is implied. The setnetgrent function also sets the offset to the first member of the netgroup.
The function innetgr searches for a match of all fields within the specified group. If any of the host, user, or domain arguments are (char *)0 those fields will match any string value in the netgroup member.
The function getnetgrent returns 0 for no more netgroup members and 1 otherwise. The function innetgr returns 1 for a successful match and 0 otherwise. The functions setnetgrent and endnetgrent have no return value.