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

PROLOG         top

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

NAME         top

       inet_addr, inet_ntoa — IPv4 address manipulation

SYNOPSIS         top

       #include <arpa/inet.h>

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

DESCRIPTION         top

       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 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 "".

       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 "".

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

       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

RETURN VALUE         top

       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         top

       No errors are defined.

       The following sections are informative.

EXAMPLES         top



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

RATIONALE         top




SEE ALSO         top

       endhostent(3p), endnetent(3p)

       The Base Definitions volume of POSIX.1‐2008, arpa_inet.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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 .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see .

IEEE/The Open Group                 2013                       INET_ADDR(3P)