# inet_addr

## 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.
    


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