inet(3N)							      inet(3N)

NAME    [Toc]    [Back]

     inet: inet_addr, inet_network, inet_makeaddr, inet_lnaof, inet_netof,
     inet_ntoa - Internet address manipulation

SYNOPSIS    [Toc]    [Back]

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

     unsigned long inet_addr(char *cp);
     unsigned long inet_network(char *cp);

     struct in_addr inet_makeaddr(int net, int lna);
     int inet_lnaof(struct in_addr in);

     int inet_netof(struct in_addr in);
     char *inet_ntoa(struct in_addr in);

DESCRIPTION    [Toc]    [Back]

     The routines inet_addr and	inet_network each interpret character strings
     representing numbers expressed in the Internet standard `.'  notation,
     returning numbers suitable	for use	as Internet addresses and Internet
     network numbers, respectively.  The routine inet_makeaddr takes an
     Internet network 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, respectively.

     The routine inet_ntoa returns a pointer to	a string in the	base 256
     notation "d<b>.d<b>.d<b>.d<b>"	described below.

     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    [Toc]    [Back]

     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.

     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	network	addresses as "128.net.host".



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inet(3N)							      inet(3N)



     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
     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 (that is, a	leading	0x or
     0X	implies	hexadecimal; otherwise,	a leading 0 implies octal; otherwise,
     the number	is interpreted as decimal).

SEE ALSO    [Toc]    [Back]

     gethostent(3N), getnetent(3N), hosts(4), networks(4)

DIAGNOSTICS    [Toc]    [Back]

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

NOTES    [Toc]    [Back]

     The problem of host byte ordering versus network byte ordering 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 return	value from inet_ntoa points to static information which	is
     overwritten in each call.


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