inet_addr, inet_network, inet_ntoa, inet_makeaddr, inet_lnaof,
inet_netof - Internet address manipulation routines

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

unsigned long inet_addr(cp)
const char *cp;

unsigned long inet_network(cp)
const char *cp;

char *inet_ntoa(in)
struct in_addr in;

struct in_addr inet_makeaddr(net, lna)
int net, lna;

unsigned long inet_lnaof(in)
struct in_addr in;

unsigned long inet_netof(in)
struct in_addr in;

The routines inet_addr and inet_network each interpret character
strings representing numbers expressed in the Internet standard "."
notation, returning numbers suitable for use as Internet addresses
and Internet network numbers, respectively. The routine inet_ntoa
takes an Internet address and returns an ASCII string representing
the address in "." notation. The routine inet_makeaddr takes an
Internet network number and a local network address and constructs
an Internet address from it. The routines inet_netof and
inet_lnaof break apart Internet host addresses, returning the
network number and local network address part, respectively.

All Internet address 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.

Values specified using the "." notation take one of the following
When four parts are specified, each is interpreted as a byte of
data and assigned, from left to right, to the four bytes of an
Internet address.

When a three part address is specified, the last part is
interpreted as a 16-bit quantity and placed in the right most two
bytes of the network address. This makes the three part address
format convenient for specifying Class B network addresses as

When a two part address is supplied, the last part is interpreted
as a 24-bit quantity and placed in the right most three bytes of
the network address. This makes the two part address format
convenient for specifying Class A network addresses as "".

When only one part is given, the value is stored directly in the
network address without any byte rearrangement.

All numbers supplied as "parts" in a "." notation may be decimal,
octal, or hexadecimal, as specified in the C language (i.e., a
leading 0x or 0X implies hexadecimal; otherwise, a leading 0
implies octal; otherwise, the number is interpreted as decimal).

gethostbyname(3), getnetent(3), hosts(5), networks(5)

The constant INADDR_NONE is returned by inet_addr and inet_network
for malformed requests.

The problem of host byte ordering versus network byte ordering is
confusing. A simple way to specify Class C network addresses in a
manner similar to that for Class B and Class A is needed. The
string returned by inet_ntoa resides in a static memory area.
Inet_addr should return a struct in_addr.