1INET_PTON(3) Linux Programmer's Manual INET_PTON(3)
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6 inet_pton - convert IPv4 and IPv6 addresses from text to binary form
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9 #include <arpa/inet.h>
10 int inet_pton(int af, const char *src, void *dst);
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14 This function converts the character string src into a network address
15 structure in the af address family, then copies the network address
16 structure to dst. The af argument must be either AF_INET or AF_INET6.
17 The following address families are currently supported:
19 AF_INET
21 src points to a character string containing an IPv4 network
22 address in dotted-decimal format, "ddd.ddd.ddd.ddd", where ddd
23 is a decimal number of up to three digits in the range 0 to 255.
24 The address is converted to a struct in_addr and copied to dst,
25 which must be sizeof(struct in_addr)[24m (4) bytes (32 bits) long.
26 AF_INET6
28 src points to a character string containing an IPv6 network
29 address. The address is converted to a struct in6_addr and
30 copied to dst, which must be sizeof(struct in6_addr)[24m (16) bytes
31 (128 bits) long. The allowed formats for IPv6 addresses follow
32 these rules:
33 1. The preferred format is x:x:x:x:x:x:x:x. This form consists
35 of eight hexadecimal numbers, each of which expresses a
36 16-bit value (i.e., each x can be up to 4 hex digits).
37 2. A series of contiguous zero values in the preferred format
39 can be abbreviated to ::. Only one instance of :: can occur
40 in an address. For example, the loopback address
41 0:0:0:0:0:0:0:1 can be abbreviated as ::1. The wildcard
42 address, consisting of all zeroes, can be written as ::.
43 3. An alternate format is useful for expressing IPv4-mapped IPv6
45 addresses. This form is written as x:x:x:x:x:x:d.d.d.d,
46 where the six leading xs are hexadecimal values that define
47 the six most-significant 16-bit pieces of the address (i.e.,
48 96 bits), and the ds express a value in dotted-decimal nota‐
49 tion that defines the least significant 32 bits of the
50 address. An example of such an address is
51 ::FFFF:204.152.189.116.
52 See RFC 2373 for further details on the representation of IPv6
54 addresses.
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57 inet_pton() returns 1 on success (network address was successfully con‐
58 verted). 0 is returned if src does not contain a character string rep‐
59 resenting a valid network address in the specified address family. If
60 af does not contain a valid address family, -1 is returned and errno is
61 set to EAFNOSUPPORT.
62
64 POSIX.1-2001.
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67 Unlike inet_aton(3) and inet_addr(3), inet_pton() supports IPv6
68 addresses. On the other hand, inet_pton() only accepts IPv4 addresses
69 in dotted-decimal notation, whereas inet_aton(3) and inet_addr(3) allow
70 the more general numbers-and-dots notation (hexadecimal and octal num‐
71 ber formats, and formats that don't require all four bytes to be
72 explicitly written). For an interface that handles both IPv6
73 addresses, and IPv4 addresses in numbers-and-dots notation, see getad‐
74 drinfo(3).
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77 AF_INET6 does not recognize IPv4 addresses. An explicit IPv4-mapped
78 IPv6 address must be supplied in src instead.
79
81 The program below demonstrates the use of inet_pton() and inet_ntop(3).
82 Here are some example runs:
83 $ ./a.out i6 0:0:0:0:0:0:0:0
85 ::
86 $ ./a.out i6 1:0:0:0:0:0:0:8
87 1::8
88 $ ./a.out i6 0:0:0:0:0:FFFF:204.152.189.116
89 ::ffff:204.152.189.116
90 Program source
92 #include <arpa/inet.h>
94 #include <stdio.h>
95 #include <stdlib.h>
96 #include <string.h>
97 int
99 main(int argc, char *argv[])
100 {
101 unsigned char buf[sizeof(struct in6_addr)];
102 int domain, s;
103 char str[INET6_ADDRSTRLEN];
104 if (argc != 3) {
106 fprintf(stderr, "Usage: %s {i4|i6|<num>} string\n", argv[0]);
107 exit(EXIT_FAILURE);
108 }
109 domain = (strcmp(argv[1], "i4") == 0) ? AF_INET :
111 (strcmp(argv[1], "i6") == 0) ? AF_INET6 : atoi(argv[1]);
112 s = inet_pton(domain, argv[2], buf);
114 if (s <= 0) {
115 if (s == 0)
116 fprintf(stderr, "Not in presentation format");
117 else
118 perror("inet_pton");
119 exit(EXIT_FAILURE);
120 }
121 if (inet_ntop(domain, buf, str, INET6_ADDRSTRLEN) == NULL) {
123 perror("inet_ntop");
124 exit(EXIT_FAILURE);
125 }
126 printf("%s\n", str);
128 exit(EXIT_SUCCESS);
130 }
131
133 getaddrinfo(3), inet(3), inet_ntop(3)
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136 This page is part of release 3.25 of the Linux man-pages project. A
137 description of the project, and information about reporting bugs, can
138 be found at http://www.kernel.org/doc/man-pages/.
139Linux 2008-06-18 INET_PTON(3)