man3p/inet_addr.3p

   1 .\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
   2 .TH "INET_ADDR" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
   3 .\" inet_addr
   4 .SH NAME
   5 inet_addr, inet_ntoa \- IPv4 address manipulation
   6 .SH SYNOPSIS
   7 .LP
   8 \fB#include <arpa/inet.h>
   9 .br
  10 .sp
  11 in_addr_t inet_addr(const char *\fP\fIcp\fP\fB);
  12 .br
  13 char *inet_ntoa(struct in_addr\fP \fIin\fP\fB);
  14 .br
  15 \fP
  16 .SH DESCRIPTION
  17 .LP
  18 The \fIinet_addr\fP() function shall convert the string pointed to
  19 by \fIcp\fP, in the standard IPv4 dotted decimal notation,
  20 to an integer value suitable for use as an Internet address.
  21 .LP
  22 The \fIinet_ntoa\fP() function shall convert the Internet host address
  23 specified by \fIin\fP to a string in the Internet
  24 standard dot notation.
  25 .LP
  26 The \fIinet_ntoa\fP() function need not be reentrant. A function that
  27 is not required to be reentrant is not required to be
  28 thread-safe.
  29 .LP
  30 All Internet addresses shall be returned in network order (bytes ordered
  31 from left to right).
  32 .LP
  33 Values specified using IPv4 dotted decimal notation take one of the
  34 following forms:
  35 .TP 7
  36 \fBa.b.c.d\fP
  37 When four parts are specified, each shall be interpreted as a byte
  38 of data and assigned, from left to right, to the four bytes
  39 of an Internet address.
  40 .TP 7
  41 \fBa.b.c\fP
  42 When a three-part address is specified, the last part shall be interpreted
  43 as a 16-bit quantity and placed in the rightmost two
  44 bytes of the network address. This makes the three-part address format
  45 convenient for specifying Class B network addresses as
  46 \fB"128.net.host"\fP .
  47 .TP 7
  48 \fBa.b\fP
  49 When a two-part address is supplied, the last part shall be interpreted
  50 as a 24-bit quantity and placed in the rightmost three
  51 bytes of the network address. This makes the two-part address format
  52 convenient for specifying Class A network addresses as
  53 \fB"net.host"\fP .
  54 .TP 7
  55 \fBa\fP
  56 When only one part is given, the value shall be stored directly in
  57 the network address without any byte rearrangement.
  58 .sp
  59 .LP
  60 All numbers supplied as parts in IPv4 dotted decimal notation may
  61 be decimal, octal, or hexadecimal, as specified in the
  62 ISO\ C standard (that is, a leading 0x or 0X implies hexadecimal;
  63 otherwise, a leading \fB'0'\fP implies octal; otherwise,
  64 the number is interpreted as decimal).
  65 .SH RETURN VALUE
  66 .LP
  67 Upon successful completion, \fIinet_addr\fP() shall return the Internet
  68 address. Otherwise, it shall return (
  69 \fBin_addr_t\fP)(-1).
  70 .LP
  71 The \fIinet_ntoa\fP() function shall return a pointer to the network
  72 address in Internet standard dot notation.
  73 .SH ERRORS
  74 .LP
  75 No errors are defined.
  76 .LP
  77 \fIThe following sections are informative.\fP
  78 .SH EXAMPLES
  79 .LP
  80 None.
  81 .SH APPLICATION USAGE
  82 .LP
  83 The return value of \fIinet_ntoa\fP() may point to static data that
  84 may be overwritten by subsequent calls to
  85 \fIinet_ntoa\fP().
  86 .SH RATIONALE
  87 .LP
  88 None.
  89 .SH FUTURE DIRECTIONS
  90 .LP
  91 None.
  92 .SH SEE ALSO
  93 .LP
  94 \fIendhostent\fP() , \fIendnetent\fP() , the Base Definitions
  95 volume of IEEE\ Std\ 1003.1-2001, \fI<arpa/inet.h>\fP
  96 .SH COPYRIGHT
  97 Portions of this text are reprinted and reproduced in electronic form
  98 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
  99 -- Portable Operating System Interface (POSIX), The Open Group Base
 100 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
 101 Electrical and Electronics Engineers, Inc and The Open Group. In the
 102 event of any discrepancy between this version and the original IEEE and
 103 The Open Group Standard, the original IEEE and The Open Group Standard
 104 is the referee document. The original Standard can be obtained online at
 105 http://www.opengroup.org/unix/online.html .