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



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

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 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
                 rearrangement.

       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
       ''00'' 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 POSIX.1-2017, <arpa_inet.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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.opengroup.org/unix/online.html .

       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
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                         INET_ADDR(3)
