— routines for manipulating
classful Internet Protocol version 4 (IPv4) addresses
As originally designed, IP version 4 split each address into a network part and local network address part, encoding that split into the address itself. It is frequency-encoded; the most-significant bit is clear in Class A addresses, in which the high-order 8 bits are the network number. Class B addresses use the high-order 16 bits as the network field, and Class C addresses have a 24-bit network part.
takes an Internet network number and a local network address and constructs
an Internet address from it.
break apart Internet host addresses, returning the network number and local
network address part, respectively.
All Internet addresses are returned in network order (bytes ordered from left to right). All network numbers and local address parts are returned as machine format integer values.
getnetent(3), inet_addr(3), inet_net(3), hosts(5), networks(5)
functions appeared in 4.2BSD.