inet_addr, inet_network, inet_ntoa, inet_makeaddr, inet_lnaof,
inet_netof - Internet address manipulation routines
struct in_addr inet_addr(cp)
struct inet_addr in;
struct in_addr inet_makeaddr(net, lna)
int net, lna;
struct in_addr 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
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. Note that when an Internet address is viewed as a 32-bit
integer quantity on the VAX the bytes referred to above appear as
"d.c.b.a". That is, VAX bytes are ordered from right to left.
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 spec-
ifying Class B network 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 speci-
fying Class A network addresses as "net.host".
When only one part is given, the value is stored directly in the net-
work 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).
gethostent(3N), getnetent(3N), hosts(5), networks(5),
The value -1 is returned by inet_addr and inet_network for malformed
The problem of host byte ordering versus network byte ordering is con-
fusing. 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.
4th Berkeley Distribution 18 July 1983 INET(3N)