inet(3N) NETWORK FUNCTIONS inet(3N)
NAME
inet: inet_addr, inet_network, inet_makeaddr, inet_lnaof,
inet_netof, inet_ntoa - Internet address manipulation
SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
unsigned long
inet_addr(cp)
char *cp;
inet_network(cp)
char *cp;
struct in_addr
inet_makeaddr(net, lna)
int net, lna;
inet_lnaof(in)
struct in_addr in;
inet_netof(in)
struct in_addr in;
char *
inet_ntoa(in)
struct in_addr in;
DESCRIPTION
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_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, respec-
tively. The routine inet_ntoa() returns a pointer to a
string in the base 256 notation "d.d.d.d" described below.
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.
INTERNET ADDRESSES
Values specified using the `.' notation take one of the
following forms:
a.b.c.d
a.b.c
a.b
a
When four parts are specified, each is interpreted as a
byte of data and assigned, from left to right, to the
Last change: User Environment Utilities 1
inet(3N) NETWORK FUNCTIONS inet(3N)
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 net-
work addresses as "128.net.host". 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 net-
work addresses as "net.host". 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
(that is, a leading 0x or 0X implies hexadecimal; oth-
erwise, a leading 0 implies octal; otherwise, the
number is interpreted as decimal).
SEE ALSO
gethostent(3N), getnetent(3N), hosts(4), networks(4)
DIAGNOSTICS
The value -1 is returned by inet_addr() and inet_network()
for malformed requests.
BUGS
The problem of host byte ordering versus network byte order-
ing 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 return value from inet_ntoa() points to
static information which is overwritten in each call.
Last change: User Environment Utilities 2