inet(3N)                                                 inet(3N)



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

     SYNOPSIS
          #include <sys/types.h>
          #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)
          int net, lna;

          int inet_lnaof(in)
          struct in_addr in;

          int 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, respective-
          ly.  The routine inet_ntoa takes an Internet address and re-
          turns an ASCII string representing the address in . nota-
          tion.  The routine inet_makeaddr takes an Internet network
          number and a local network address and constructs an Inter-
          net 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.

          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



     April, 1990                                                     1

     inet(3N)                                                 inet(3N)



             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 in-
          terpreted 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 ad-
          dresses 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 ad-
          dresses 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 de-
          cimal, octal, or hexadecimal, as specified in the C language
          (that is, a leading 0x or 0X implies hexadecimal; a leading
          0 implies octal; otherwise, the number is interpreted as de-
          cimal).

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

     SEE ALSO
          getnetent(3N), hosts(4N), networks(4N).

     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 Class B and Class A is
          needed.  The string returned by inet_ntoa resides in a stat-
          ic memory area.














     2                                                     April, 1990