inet_addr(3p) — Linux manual page

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 (consult 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 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 '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(3p), endnetent(3p)

       The Base Definitions volume of POSIX.1‐2017, arpa_inet.h(0p)

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(3P)

Pages that refer to this page: arpa_inet.h(0p), endservent(3p), freeaddrinfo(3p), inet_ntop(3p)

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