inet(3N)                NETWORK FUNCTIONS                inet(3N)



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

SYNOPSIS
     #include <sys/types.h>
     #include <sys/socket.h>
     #include <netinet/in.h>
     #include <arpa/inet.h>
     unsigned long
     inet_addr(cp)
     char *cp;
     inet_network(cp)
     char *cp;
     struct in_addr
     inet_makeaddr(net, lna)
     int net, lna;
     inet_lnaof(in)
     struct in_addr in;
     inet_netof(in)
     struct in_addr in;
     char *
     inet_ntoa(in)
     struct in_addr in;

DESCRIPTION
     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,  respec-
     tively.   The  routine  inet_ntoa()  returns  a pointer to a
     string in the base 256 notation "d.d.d.d"  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
     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



             Last change: User Environment Utilities            1

inet(3N)                NETWORK FUNCTIONS                inet(3N)



          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  net-
          work  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 specifying Class A net-
          work 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; oth-
          erwise, a  leading  0  implies  octal;  otherwise,  the
          number is interpreted as decimal).

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

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 return value from inet_ntoa() points to
     static information which is overwritten in each call.























             Last change: User Environment Utilities            2