inet_lnaof, inet_netof

Purpose

     Manipulation subroutines for Internet addresses.

Library

     Sockets Library (libsock.a)

Syntax

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

     struct in_addr inet_addr (cp)        struct in_addr inet_makeaddr (net, lna)
     char *cp;                            int net, lna;

     int inet_network (cp)                int inet_lnaof (in)
     char *cp;                            struct in_addr in;

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

     The inet_addr and inet_network subroutines each interpret
     character strings  representing numbers expressed  in the
     Internet  standard dot  (.)  notation, returning  numbers
     suitable  for  use  as Internet  addresses  and  Internet
     network numbers.  The cp parameter represents a string of
     characters in the Internet address form.

     The inet_ntoa  subroutine takes  an Internet  address and
     returns an  ASCII string representing the  address in dot
     notation.  The in parameter contains the Internet address
     to be converted to ASCII.

     The inet_makeaddr takes an  Internet network number and a
     local network address and  constructs an Internet address
     from it.  The net  parameter contains an Internet network
     number, while the lna  parameter contains a local network
     address.

     The  inet_netof and  inet_lnaof  subroutines break  apart
     Internet  addresses,  returning  the network  number  and
     local network address part.   The in parameter represents
     the Internet address to separate.

     All  Internet addresses  are returned  in network  order,
     with  the  first byte  being  the  high-order byte.   All
     network  numbers  and  local addresses  are  returned  as
     integer values in machine format.

     The values specified  using the dot 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  to  the  four bytes  of  an
     Internet address, ordered from high-order to low-order.

     When a three-part address is  specified, the last part is
     interpreted as a 16-bit quantity  and placed in the right
     two bytes of the network  address.  This makes the three-
     part  address format  convenient for  specifying 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
     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 for each  part of a dot notation may
     be decimal, octal, or hexadecimal, as specified in C lan-
     guage.   A leading  "0x" or  "0X" implies  hexadecimal, a
     leading "0"  implies octal,  and anything else  is inter-
     preted as decimal.

     Return Value

     The inet_addr and inet_network subroutines return numbers
     suitable  for  use  as Internet  addresses  and  Internet
     network  numbers,  respectively,   on  success.   If  the
     inet_addr or inet_network subroutine fails, a value of -1
     is returned.

     Related Information

     In   this   book:     "   gethostbyaddr,   gethostbyname,
     sethostent, endhostent .*5a, gethostent," and "getnetent,
     getnetbyaddr, getnetbyname, setnetent, endnetent."

     The discussion of /etc/hosts  and /etc/networks in Inter-
     face Program for use with TCP/IP.