inet_makeaddr(3)                                       inet_makeaddr(3)

  inet_aton()

  NAME

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

  SYNOPSIS

    #include 
    #include 
    #include 

    int inet_aton (char *cp, struct in_addr *pin)
    unsigned long inet_addr (char *cp)
    unsigned long inet_network (char *cp)
    char * inet_ntoa (struct in_addr in)
    struct in_addr inet_makeaddr (int net, int lna)
    unsigned long inet_lnaof (struct in_addr in)
    unsigned long inet_netof (struct in_addr in)

  DESCRIPTION

    The routines inet_aton(3), inet_addr(3) and inet_network(3) interpret
    character strings representing numbers expressed in the Internet standard
    . notation. The inet_aton(3) routine interprets the specified character
    string as an Internet address, placing the address into the structure
    provided. It returns 1 if the string was successfully interpreted, or 0 if
    the string is invalid. The inet_addr(3) and inet_network(3) functions
    return numbers suitable for use as Internet addresses and Internet network
    numbers, respectively. The routine inet_ntoa(3) takes an Internet address
    and returns an ASCII string representing the address in . notation. The
    routine inet_makeaddr(3) takes an Internet network number and a local
    network address and constructs an Internet address from it. The routines
    inet_netof(3) and inet_lnaof(3) break apart Internet host addresses,
    returning the network number and local network address part, respectively.

    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 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.

    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 can 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.

  RETURN VALUES

    The constant INADDR_NONE is returned by inet_addr(3) and inet_network(3)
    for malformed requests.

  NOTES

    The value INADDR_NONE (0xffffffff) is a valid broadcast address, but
    inet_addr(3) cannot return that value without indicating failure. The
    newer inet_aton(3) function does not share this problem. The problem of
    host byte ordering compared to network byte ordering is confusing. The
    string returned by inet_ntoa(3) resides in a static memory area.

    Inet_addr should return a struct in_addr.

  SEE ALSO

    gethostbyname(2)

  USAGE NOTES

    The following functions are thread safe: inet_addr, inet_aton, inet_lnaof,
    inet_makeaddr, inet_netof, inet_network. The inet_ntoa function is not
    thread safe.

    None of these functions are async-signal safe.