1INET_NTOP(3P) POSIX Programmer's Manual INET_NTOP(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 inet_ntop, inet_pton - convert IPv4 and IPv6 addresses between binary
13 and text form
14
16 #include <arpa/inet.h>
17 const char *inet_ntop(int af, const void *restrict src,
19 char *restrict dst, socklen_t size);
20 int inet_pton(int af, const char *restrict src, void *restrict dst);
21
24 The inet_ntop() function shall convert a numeric address into a text
25 string suitable for presentation. The af argument shall specify the
26 family of the address. This can be AF_INET or AF_INET6. The src argu‐
27 ment points to a buffer holding an IPv4 address if the af argument is
28 AF_INET, or an IPv6 address if the af argument is AF_INET6; the
29 address must be in network byte order. The dst argument points to a
30 buffer where the function stores the resulting text string; it shall
31 not be NULL. The size argument specifies the size of this buffer, which
32 shall be large enough to hold the text string (INET_ADDRSTRLEN charac‐
33 ters for IPv4, INET6_ADDRSTRLEN characters for IPv6).
34 The inet_pton() function shall convert an address in its standard text
36 presentation form into its numeric binary form. The af argument shall
37 specify the family of the address. The AF_INET and AF_INET6 address
38 families shall be supported. The src argument points to the string
39 being passed in. The dst argument points to a buffer into which the
40 function stores the numeric address; this shall be large enough to hold
41 the numeric address (32 bits for AF_INET, 128 bits for AF_INET6).
42 If the af argument of inet_pton() is AF_INET, the src string shall be
44 in the standard IPv4 dotted-decimal form:
45 ddd.ddd.ddd.ddd
48 where "ddd" is a one to three digit decimal number between 0 and 255
50 (see inet_addr()). The inet_pton() function does not accept other for‐
51 mats (such as the octal numbers, hexadecimal numbers, and fewer than
52 four numbers that inet_addr() accepts).
53 If the af argument of inet_pton() is AF_INET6, the src string shall be
55 in one of the following standard IPv6 text forms:
56 1. The preferred form is "x:x:x:x:x:x:x:x", where the 'x' s are the
58 hexadecimal values of the eight 16-bit pieces of the address. Lead‐
59 ing zeros in individual fields can be omitted, but there shall be
60 at least one numeral in every field.
61 2. A string of contiguous zero fields in the preferred form can be
63 shown as "::" . The "::" can only appear once in an address.
64 Unspecified addresses ( "0:0:0:0:0:0:0:0" ) may be represented sim‐
65 ply as "::" .
66 3. A third form that is sometimes more convenient when dealing with a
68 mixed environment of IPv4 and IPv6 nodes is "x:x:x:x:x:x:d.d.d.d",
69 where the 'x' s are the hexadecimal values of the six high-order
70 16-bit pieces of the address, and the 'd' s are the decimal values
71 of the four low-order 8-bit pieces of the address (standard IPv4
72 representation).
73 Note: A more extensive description of the standard representations of
75 IPv6 addresses can be found in RFC 2373.
76
79 The inet_ntop() function shall return a pointer to the buffer contain‐
80 ing the text string if the conversion succeeds, and NULL otherwise, and
81 set errno to indicate the error.
82 The inet_pton() function shall return 1 if the conversion succeeds,
84 with the address pointed to by dst in network byte order. It shall
85 return 0 if the input is not a valid IPv4 dotted-decimal string or a
86 valid IPv6 address string, or -1 with errno set to [EAFNOSUPPORT] if
87 the af argument is unknown.
88
90 The inet_ntop() and inet_pton() functions shall fail if:
91 EAFNOSUPPORT
93 The af argument is invalid.
95 ENOSPC The size of the inet_ntop() result buffer is inadequate.
97 The following sections are informative.
100
102 None.
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105 None.
106
108 None.
109
111 None.
112
114 The Base Definitions volume of IEEE Std 1003.1-2001, <arpa/inet.h>
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117 Portions of this text are reprinted and reproduced in electronic form
118 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
119 -- Portable Operating System Interface (POSIX), The Open Group Base
120 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
121 Electrical and Electronics Engineers, Inc and The Open Group. In the
122 event of any discrepancy between this version and the original IEEE and
123 The Open Group Standard, the original IEEE and The Open Group Standard
124 is the referee document. The original Standard can be obtained online
125 at http://www.opengroup.org/unix/online.html .
126IEEE/The Open Group 2003 INET_NTOP(3P)