1INET(3N) INET(3N)
2
6 inet_addr, inet_network, inet_ntoa, inet_makeaddr, inet_lnaof,
7 inet_netof - Internet address manipulation routines
8
10 #include <sys/socket.h>
11 #include <netinet/in.h>
12 #include <arpa/inet.h>
13 unsigned long inet_addr(cp)
15 char *cp;
16 unsigned long inet_network(cp)
18 char *cp;
19 char *inet_ntoa(in)
21 struct in_addr in;
22 struct in_addr inet_makeaddr(net, lna)
24 long net, lna;
25 long inet_lnaof(in)
27 struct in_addr in;
28 long inet_netof(in)
30 struct in_addr in;
31
33 The routines inet_addr and inet_network each interpret character
34 strings representing numbers expressed in the Internet standard “.”
35 notation, returning numbers suitable for use as Internet addresses and
36 Internet network numbers, respectively. The routine inet_ntoa takes an
37 Internet address and returns an ASCII string representing the address
38 in “.” notation. The routine inet_makeaddr takes an Internet network
39 number and a local network address and constructs an Internet address
40 from it. The routines inet_netof and inet_lnaof break apart Internet
41 host addresses, returning the network number and local network address
42 part, respectively.
43 All Internet address are returned in network order (bytes ordered from
45 left to right). All network numbers and local address parts are
46 returned as machine format integer values.
47
49 Values specified using the “.” notation take one of the following
50 forms:
51 a.b.c.d
52 a.b.c
53 a.b
54 a
55 When four parts are specified, each is interpreted as a byte of data
56 and assigned, from left to right, to the four bytes of an Internet
57 address. Note that when an Internet address is viewed as a 32-bit
58 integer quantity on the VAX the bytes referred to above appear as
59 “d.c.b.a”. That is, VAX bytes are ordered from right to left.
60 When a three part address is specified, the last part is interpreted as
62 a 16-bit quantity and placed in the right most two bytes of the network
63 address. This makes the three part address format convenient for spec‐
64 ifying Class B network addresses as “128.net.host”.
65 When a two part address is supplied, the last part is interpreted as a
67 24-bit quantity and placed in the right most three bytes of the network
68 address. This makes the two part address format convenient for speci‐
69 fying Class A network addresses as “net.host”.
70 When only one part is given, the value is stored directly in the net‐
72 work address without any byte rearrangement.
73 All numbers supplied as “parts” in a “.” notation may be decimal,
75 octal, or hexadecimal, as specified in the C language (i.e., a leading
76 0x or 0X implies hexadecimal; otherwise, a leading 0 implies octal;
77 otherwise, the number is interpreted as decimal).
78
80 gethostbyname(3N), getnetent(3N), hosts(5), networks(5),
81
83 The value -1 is returned by inet_addr and inet_network for malformed
84 requests.
85
87 The problem of host byte ordering versus network byte ordering is con‐
88 fusing. A simple way to specify Class C network addresses in a manner
89 similar to that for Class B and Class A is needed. The string returned
90 by inet_ntoa resides in a static memory area.
91 Inet_addr should return a struct in_addr.
924.2 Berkeley Distribution May 27, 1986 INET(3N)