INET(3)                     BSD Programmer's Manual                    INET(3)

NAME
     inetaton, inetaddr, inetnetwork, inetntoa, inetmakeaddr, inetlnaof,
     inetnetof - Internet address manipulation routines

SYNOPSIS
     #include <sys/socket.h>
     #include <netinet/in.h>
     #include <arpa/inet.h>

     unsigned long
     inetaton(const char *cp, struct inaddr *pin)

     unsigned long
     inetaddr(const char *cp)

     unsigned long
     inetnetwork(const char *cp)

     char *
     inetntoa(struct inaddr in)

     struct inaddr
     inetmakeaddr(int net, int lna)

     unsigned long
     inetlnaof(struct inaddr in)

     unsigned long
     inetnetof(struct inaddr in)

DESCRIPTION
     The routines inetaton(), inetaddr() and inetnetwork() interpret char-
     acter strings representing numbers expressed in the Internet standard `.'
     notation.  The inetaton() routine interprets the specified character
     string as an Internet address, placing the address into the structure
     provided.  It returns 1 if the string was successfully interpreted, or 0
     if the string is invalid.  The inetaddr() and inetnetwork() functions
     return numbers suitable for use as Internet addresses and Internet net-
     work numbers, respectively.  The routine inetntoa() takes an Internet
     address and returns an ASCII string representing the address in `.' nota-
     tion.  The routine inetmakeaddr() takes an Internet network number and a
     local network address and constructs an Internet address from it.  The
     routines inetnetof() and inetlnaof() break apart Internet host address-
     es, returning the network number and local network address part, respec-
     tively.

     All Internet addresses are returned in network order (bytes ordered from
     left to right).  All network numbers and local address parts are returned
     as machine format integer values.

INTERNET ADDRESSES
     Values specified using the `.' notation take one of the following forms:

           a.b.c.d
           a.b.c
           a.b
           a

     When four parts are specified, each is interpreted as a byte of data and
     assigned, from left to right, to the four bytes of an Internet address.
     Note that when an Internet address is viewed as a 32-bit integer quantity
     on the VAX the bytes referred to above appear as ``d.c.b.a''. That is,
     VAX bytes are ordered from right to left.

     When a three part address is specified, the last part is interpreted as a
     16-bit quantity and placed in the right-most two bytes of the network ad-
     dress.  This makes the three part address format convenient for specify-
     ing Class B network addresses as ``128.net.host''.

     When a two part address is supplied, the last part is interpreted as a
     24-bit quantity and placed in the right most three bytes of the network
     address.  This makes the two part address format convenient for specify-
     ing Class A network addresses as ``net.host''.

     When only one part is given, the value is stored directly in the network
     address without any byte rearrangement.

     All numbers supplied as ``parts'' in a `.' notation may be decimal, oc-
     tal, or hexadecimal, as specified in the C language (i.e., a leading 0x
     or 0X implies hexadecimal; otherwise, a leading 0 implies octal; other-
     wise, the number is interpreted as decimal).

DIAGNOSTICS
     The constant INADDR_NONE is returned by inetaddr() and inetnetwork()
     for malformed requests.

SEE ALSO
     gethostbyname(3),  getnetent(3),  hosts(5),  networks(5)

HISTORY
     These functions appeared in 4.2BSD.

BUGS
     The value INADDR_NONE (0xffffffff) is a valid broadcast address, but
     inetaddr() cannot return that value without indicating failure.  The
     newer inetaton() function does not share this problem.

     The problem of host byte ordering versus network byte ordering is confus-
     ing.

     The string returned by inetntoa() resides in a static memory area.

     Inet_addr should return a struct inaddr.

4.2 Berkeley Distribution       March 26, 1993                               2