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, respectively. 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
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 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 return value from inet_ntoa() points to static information which is overwritten in each call.