2.11BSD#431 - /usr/man/cat3/ntoa.0

INET(3N)	    UNIX Programmer's Manual		 INET(3N)


NAME
     inet_addr, inet_network, inet_ntoa, inet_makeaddr,
     inet_lnaof, inet_netof - Internet address manipulation rou-
     tines

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

     unsigned long inet_addr(cp)
     char *cp;

     unsigned long inet_network(cp)
     char *cp;

     char *inet_ntoa(in)
     struct in_addr in;

     struct in_addr inet_makeaddr(net, lna)
     long net, lna;

     long inet_lnaof(in)
     struct in_addr in;

     long inet_netof(in)
     struct in_addr in;

DESCRIPTION
     The routines inet_addr and inet_network each interpret char-
     acter strings representing numbers expressed in the Internet
     standard "." notation, returning numbers suitable for use as
     Internet addresses and Internet network numbers, respec-
     tively.  The routine inet_ntoa takes an Internet address and
     returns an ASCII string representing the address in "."
     notation.	The routine inet_makeaddr takes an Internet net-
     work number and a local network address and constructs an
     Internet address from it.	The routines inet_netof and
     inet_lnaof break apart Internet host addresses, returning
     the network number and local network address part, respec-
     tively.

     All Internet address 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 fol-
     lowing forms:
	  a.b.c.d
	  a.b.c
	  a.b


Printed 11/26/99	  May 27, 1986				1


INET(3N)	    UNIX Programmer's Manual		 INET(3N)


	  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 address.  This makes the three
     part address format convenient for specifying Class B net-
     work addresses as "128.net.host".

     When a two part address is supplied, the last part is inter-
     preted 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 specifying 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, octal, or hexadecimal, as specified in the C
     language (i.e., a leading 0x or 0X implies hexadecimal; oth-
     erwise, a leading 0 implies octal; otherwise, the number is
     interpreted as decimal).

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

DIAGNOSTICS
     The value -1 is returned by inet_addr and inet_network for
     malformed requests.

BUGS
     The problem of host byte ordering versus network byte order-
     ing is confusing.	A simple way to specify Class C network
     addresses in a manner similar to that for Class B and Class
     A is needed.  The string returned by inet_ntoa resides in a
     static memory area.
     Inet_addr should return a struct in_addr.


Printed 11/26/99	  May 27, 1986				2