INET_ADDR(3P)                                       POSIX Programmer's Manual                                      INET_ADDR(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       inet_addr, inet_ntoa - IPv4 address manipulation

SYNOPSIS
       #include <arpa/inet.h>

       in_addr_t inet_addr(const char *cp);
       char *inet_ntoa(struct in_addr in);


DESCRIPTION
       The  inet_addr()  function shall convert the string pointed to by cp, in the standard IPv4 dotted decimal notation, to an
       integer value suitable for use as an Internet address.

       The inet_ntoa() function shall convert the Internet host address specified by in to a string in the Internet standard dot
       notation.

       The  inet_ntoa()  function  need  not be reentrant. A function that is not required to be reentrant is not required to be
       thread-safe.

       All Internet addresses shall be returned in network order (bytes ordered from left to right).

       Values specified using IPv4 dotted decimal notation take one of the following forms:

       a.b.c.d
              When four parts are specified, each shall be interpreted as a byte of data and assigned, from left  to  right,  to
              the four bytes of an Internet address.

       a.b.c  When  a three-part address is specified, the last part shall be interpreted as a 16-bit quantity and placed in the
              rightmost two bytes of the network address. This makes the three-part address  format  convenient  for  specifying
              Class B network addresses as "128.net.host" .

       a.b    When  a  two-part  address  is supplied, the last part shall be interpreted as a 24-bit quantity and placed in the
              rightmost three bytes of the network address. This makes the two-part address  format  convenient  for  specifying
              Class A network addresses as "net.host" .

       a      When only one part is given, the value shall be stored directly in the network address without any byte rearrange-
              ment.


       All numbers supplied as parts in IPv4 dotted decimal notation may be decimal, octal, or hexadecimal, as specified in  the
       ISO C  standard  (that is, a leading 0x or 0X implies hexadecimal; otherwise, a leading '0' implies octal; otherwise, the
       number is interpreted as decimal).

RETURN VALUE
       Upon successful completion, inet_addr() shall return the Internet address. Otherwise, it shall return ( in_addr_t)(-1).

       The inet_ntoa() function shall return a pointer to the network address in Internet standard dot notation.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The return value of inet_ntoa() may point to static data that may be overwritten by subsequent calls to inet_ntoa().

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       endhostent(), endnetent(), the Base Definitions volume of IEEE Std 1003.1-2001, <arpa/inet.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                 INET_ADDR(3P)