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
23 The inet_ntop() function shall convert a numeric address into a text
24 string suitable for presentation. The af argument shall specify the
25 family of the address. This can be AF_INET or AF_INET6. The src argu‐
26 ment points to a buffer holding an IPv4 address if the af argument is
27 AF_INET, or an IPv6 address if the af argument is AF_INET6; the address
28 must be in network byte order. The dst argument points to a buffer
29 where the function stores the resulting text string; it shall not be
30 NULL. The size argument specifies the size of this buffer, which shall
31 be large enough to hold the text string (INET_ADDRSTRLEN characters for
32 IPv4, INET6_ADDRSTRLEN characters for IPv6).
33 The inet_pton() function shall convert an address in its standard text
35 presentation form into its numeric binary form. The af argument shall
36 specify the family of the address. The AF_INET and AF_INET6 address
37 families shall be supported. The src argument points to the string
38 being passed in. The dst argument points to a buffer into which the
39 function stores the numeric address; this shall be large enough to hold
40 the numeric address (32 bits for AF_INET, 128 bits for AF_INET6).
41 If the af argument of inet_pton() is AF_INET, the src string shall be
43 in the standard IPv4 dotted-decimal form:
44 ddd.ddd.ddd.ddd
47 where "ddd" is a one to three digit decimal number between 0 and 255
49 (see inet_addr()). The inet_pton() function does not accept other for‐
50 mats (such as the octal numbers, hexadecimal numbers, and fewer than
51 four numbers that inet_addr() accepts).
52 If the af argument of inet_pton() is AF_INET6, the src string shall be
54 in one of the following standard IPv6 text forms:
55 1. The preferred form is "x:x:x:x:x:x:x:x", where the 'x's are the
57 hexadecimal values of the eight 16-bit pieces of the address.
58 Leading zeros in individual fields can be omitted, but there shall
59 be one to four hexadecimal digits in every field.
60 2. A string of contiguous zero fields in the preferred form can be
62 shown as "::". The "::" can only appear once in an address.
63 Unspecified addresses ("0:0:0:0:0:0:0:0") may be represented simply
64 as "::".
65 3. A third form that is sometimes more convenient when dealing with a
67 mixed environment of IPv4 and IPv6 nodes is "x:x:x:x:x:x:d.d.d.d",
68 where the 'x's are the hexadecimal values of the six high-order
69 16-bit pieces of the address, and the 'd's are the decimal values
70 of the four low-order 8-bit pieces of the address (standard IPv4
71 representation).
72 Note: A more extensive description of the standard representations
74 of IPv6 addresses can be found in RFC 2373.
75
77 The inet_ntop() function shall return a pointer to the buffer contain‐
78 ing the text string if the conversion succeeds, and NULL otherwise, and
79 set errno to indicate the error.
80 The inet_pton() function shall return 1 if the conversion succeeds,
82 with the address pointed to by dst in network byte order. It shall
83 return 0 if the input is not a valid IPv4 dotted-decimal string or a
84 valid IPv6 address string, or -1 with errno set to [EAFNOSUPPORT] if
85 the af argument is unknown.
86
88 The inet_ntop() and inet_pton() functions shall fail if:
89 EAFNOSUPPORT
91 The af argument is invalid.
92 ENOSPC The size of the inet_ntop() result buffer is inadequate.
94 The following sections are informative.
96
98 None.
99
101 None.
102
104 None.
105
107 None.
108
110 The Base Definitions volume of POSIX.1‐2017, <arpa_inet.h>
111
113 Portions of this text are reprinted and reproduced in electronic form
114 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
115 table Operating System Interface (POSIX), The Open Group Base Specifi‐
116 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
117 Electrical and Electronics Engineers, Inc and The Open Group. In the
118 event of any discrepancy between this version and the original IEEE and
119 The Open Group Standard, the original IEEE and The Open Group Standard
120 is the referee document. The original Standard can be obtained online
121 at http://www.opengroup.org/unix/online.html .
122 Any typographical or formatting errors that appear in this page are
124 most likely to have been introduced during the conversion of the source
125 files to man page format. To report such errors, see https://www.ker‐
126 nel.org/doc/man-pages/reporting_bugs.html .
127IEEE/The Open Group 2017 INET_NTOP(3P)