inet(3N)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(char *cp);
unsigned long inet_network(char *cp);
struct in_addr inet_makeaddr(int net, int lna);
int inet_lnaof(struct in_addr in);
int inet_netof(struct in_addr in);
char *inet_ntoa(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 network addresses as "128.net.host".
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inet(3N)inet(3N)
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 "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; otherwise, a leading 0 implies octal; otherwise,
the number is interpreted as decimal).
SEE ALSOgethostent(3N), getnetent(3N), hosts(4), networks(4)DIAGNOSTICS
The value -1 is returned by inet_addr and inet_network for malformed
requests.
NOTES
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.
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