inet(SLIB)                     6 January 1993                     inet(SLIB)


 Name

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

 Syntax


    #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 inetaddr and inetnetwork 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, respectively.  The routine inetntoa takes an Internet
    address and returns an ASCII string representing the address in dot nota-
    tion.  The routine inetmakeaddr takes an Internet network number and a
    local network address and constructs an Internet address from it.  The
    routines inetnetof and inetlnaof break apart Internet host addresses,
    returning the network number and local network address part, respec-
    tively.

    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 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, 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 speci-
    fying 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 most three bytes of the network
    address.  This makes the two part address format convenient for specify-
    ing 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 ``dot'' 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; oth-
    erwise, the number is interpreted as decimal).

 Diagnostics

    The value INADDRNONE is returned by inetaddr and inetnetwork for mal-
    formed requests.

 Notes

    The problem of host byte ordering versus network byte ordering is confus-
    ing.  A simple way to specify Class C network addresses in a manner simi-
    lar to that for Class B and Class A is needed.  The string returned by
    inetntoa resides in a static memory area.

 See also

    gethostbyname(SLIB), getnetent(SLIB), hosts(SFF), inet(ADMP) and
    networks(SFF).