1INET_ADDR(3P) POSIX Programmer's Manual INET_ADDR(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
13 inet_addr, inet_ntoa — IPv4 address manipulation
14
16 #include <arpa/inet.h>
17 in_addr_t inet_addr(const char *cp);
19 char *inet_ntoa(struct in_addr in);
20
22 The inet_addr() function shall convert the string pointed to by cp, in
23 the standard IPv4 dotted decimal notation, to an integer value suitable
24 for use as an Internet address.
25 The inet_ntoa() function shall convert the Internet host address speci‐
27 fied by in to a string in the Internet standard dot notation.
28 The inet_ntoa() function need not be thread-safe.
30 All Internet addresses shall be returned in network order (bytes
32 ordered from left to right).
33 Values specified using IPv4 dotted decimal notation take one of the
35 following forms:
36 a.b.c.d When four parts are specified, each shall be interpreted as a
38 byte of data and assigned, from left to right, to the four
39 bytes of an Internet address.
40 a.b.c When a three-part address is specified, the last part shall
42 be interpreted as a 16-bit quantity and placed in the right‐
43 most two bytes of the network address. This makes the three-
44 part address format convenient for specifying Class B network
45 addresses as "128.net.host".
46 a.b When a two-part address is supplied, the last part shall be
48 interpreted as a 24-bit quantity and placed in the rightmost
49 three bytes of the network address. This makes the two-part
50 address format convenient for specifying Class A network
51 addresses as "net.host".
52 a When only one part is given, the value shall be stored
54 directly in the network address without any byte rearrange‐
55 ment.
56 All numbers supplied as parts in IPv4 dotted decimal notation may be
58 decimal, octal, or hexadecimal, as specified in the ISO C standard
59 (that is, a leading 0x or 0X implies hexadecimal; otherwise, a leading
60 '0' implies octal; otherwise, the number is interpreted as decimal).
61
63 Upon successful completion, inet_addr() shall return the Internet
64 address. Otherwise, it shall return (in_addr_t)(−1).
65 The inet_ntoa() function shall return a pointer to the network address
67 in Internet standard dot notation.
68
70 No errors are defined.
71 The following sections are informative.
73
75 None.
76
78 The return value of inet_ntoa() may point to static data that may be
79 overwritten by subsequent calls to inet_ntoa().
80
82 None.
83
85 None.
86
88 endhostent(), endnetent()
89 The Base Definitions volume of POSIX.1‐2008, <arpa_inet.h>
91
93 Portions of this text are reprinted and reproduced in electronic form
94 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
95 -- Portable Operating System Interface (POSIX), The Open Group Base
96 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
97 cal and Electronics Engineers, Inc and The Open Group. (This is
98 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
99 event of any discrepancy between this version and the original IEEE and
100 The Open Group Standard, the original IEEE and The Open Group Standard
101 is the referee document. The original Standard can be obtained online
102 at http://www.unix.org/online.html .
103 Any typographical or formatting errors that appear in this page are
105 most likely to have been introduced during the conversion of the source
106 files to man page format. To report such errors, see https://www.ker‐
107 nel.org/doc/man-pages/reporting_bugs.html .
108IEEE/The Open Group 2013 INET_ADDR(3P)