| INET(3) | Library Functions Manual | INET(3) | 
inet_addr, inet_aton,
  inet_lnaof, inet_makeaddr,
  inet_netof, inet_network,
  inet_ntoa, inet_ntop,
  inet_pton, addr,
  ntoa, network —
#include <arpa/inet.h>
in_addr_t
  
  inet_addr(const
    char *cp);
int
  
  inet_aton(const
    char *cp, struct in_addr
    *addr);
in_addr_t
  
  inet_lnaof(struct
    in_addr in);
struct in_addr
  
  inet_makeaddr(in_addr_t
    net, in_addr_t
    lna);
in_addr_t
  
  inet_netof(struct
    in_addr in);
in_addr_t
  
  inet_network(const
    char *cp);
char *
  
  inet_ntoa(struct
    in_addr in);
const char *
  
  inet_ntop(int
    af, const void * restrict
    src, char * restrict
    dst, socklen_t
    size);
int
  
  inet_pton(int
    af, const char * restrict
    src, void * restrict
    dst);
inet_aton(),
  inet_addr() and inet_network()
  interpret character strings representing numbers expressed in the Internet
  standard “dotted quad” notation.
The inet_pton() function converts a
    presentation format address (that is, printable form as held in a character
    string) to network format (usually a struct in_addr or
    some other internal binary representation, in network byte order). It
    returns 1 if the address was valid for the specified address family, or 0 if
    the address wasn't parsable in the specified address family, or -1 if some
    system error occurred (in which case errno will have
    been set). This function is presently valid for
    AF_INET and AF_INET6.
The inet_aton() 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() and
    inet_network() functions return numbers suitable for
    use as Internet addresses and Internet network numbers, respectively.
The function inet_ntop() converts an
    address from network format (usually a struct in_addr
    or some other binary form, in network byte order) to presentation format
    (suitable for external display purposes). It returns NULL if a system error
    occurs (in which case, errno will have been set), or
    it returns a pointer to the destination string. The
    size parameter is the size of the
    buf argument.
The routine inet_ntoa() takes an Internet
    address and returns an ASCII string representing the address in
    “dotted quad” notation.
The routine inet_makeaddr() takes an
    Internet network number and a local network address (both in host order) and
    constructs an Internet address from it. Note that to convert only a single
    value to a struct in_addr form that value should be
    passed as the first parameter and ‘0L’
    should be given for the second parameter.
The routines inet_netof() and
    inet_lnaof() break apart Internet host addresses,
    returning the network number and local network address part, respectively
    (both in host order).
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.
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. Note that when an Internet address is viewed as a 32-bit integer
    quantity on a system that uses little-endian byte order (e.g. Intel i386,
    i486 and Pentium processors) the bytes referred to above appear as
    “d.c.b.a”. That is, little-endian
    bytes are ordered from right to left.
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 “dotted quad” notation may be decimal, octal, or hexadecimal, as specified in the C language (i.e., a leading 0x or 0X implies hexadecimal; otherwise, a leading 0 implies octal; otherwise, the number is interpreted as decimal).
The presentation format of an IPv6 address is given in RFC 2373:
There are three conventional forms for representing IPv6 addresses as text strings:
FEDC:BA98:7654:3210:FEDC:BA98:7654:3210
1080:0:0:0:8:800:200C:417A
    
    Note that it is not necessary to write the leading zeros in an individual field, but there must be at least one numeral in every field (except for the case described in 2).
For example the following addresses:
1080:0:0:0:8:800:200C:417A  a unicast address
FF01:0:0:0:0:0:0:43         a multicast address
0:0:0:0:0:0:0:1             the loopback address
0:0:0:0:0:0:0:0             the unspecified addresses
    
    may be represented as:
1080::8:800:200C:417A       a unicast address
FF01::43                    a multicast address
::1                         the loopback address
::                          the unspecified addresses
    
    
0:0:0:0:0:0:13.1.68.3
0:0:0:0:0:FFFF:129.144.52.38
    
    or in compressed form:
::13.1.68.3
::FFFF:129.144.52.38
    
    INADDR_NONE is returned by
  inet_addr() and inet_network()
  for malformed requests.
inet_ntop() and inet_pton()
  functions may fail with
EAFNOSUPPORT]AF_INET or AF_INET6.The inet_ntop() function may fail with
ENOSPC]IP Version 6 Addressing Architecture, RFC 2373, July 1998.
Basic Socket Interface Extensions for IPv6, RFC 3493, February 2003.
inet_ntop() and inet_pton()
  functions conform to IEEE Std 1003.1-2001
  (“POSIX.1”). Note that
  inet_pton() does not accept 1-, 2-, or 3-part dotted
  addresses; all four parts must be specified. Additionally all four parts of a
  dotted address must be decimal. This is a narrower input set than that
  accepted by inet_aton().
inet_addr(), inet_network(),
  inet_makeaddr(), inet_lnaof()
  and inet_netof() functions appeared in
  4.2BSD. They were changed to use
  in_addr_t in place of unsigned
  long in NetBSD 2.0. The
  inet_aton() and inet_ntoa()
  functions appeared in 4.3BSD. The
  inet_pton() and inet_ntop()
  functions appeared in BIND 4.9.4 and thence NetBSD
  1.3; they were also in X/Open Networking Services
  Issue 5.2 (“XNS5.2”).
INADDR_NONE (0xffffffff) is a valid broadcast
  address, but inet_addr() cannot return that value
  without indicating failure. The newer inet_aton()
  function does not share this problem.
The problem of host byte ordering versus network byte ordering is confusing.
The string returned by inet_ntoa() resides
    in a static memory area.
The function inet_addr() should return a
    struct in_addr.
The function inet_network() does not
    support byte rearrangement for one, two, and three part addresses.
| July 25, 2012 | NetBSD 9.3 |