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INET(3)		       FreeBSD Library Functions Manual		       INET(3)

NAME
     inet_aton,	inet_addr, inet_network, inet_ntoa, inet_ntoa_r, inet_ntop,
     inet_pton,	inet_makeaddr, inet_lnaof, inet_netof -- Internet address
     manipulation routines

LIBRARY
     Standard C	Library	(libc, -lc)

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

     int
     inet_aton(const char *cp, struct in_addr *pin);

     in_addr_t
     inet_addr(const char *cp);

     in_addr_t
     inet_network(const	char *cp);

     char *
     inet_ntoa(struct in_addr in);

     char *
     inet_ntoa_r(struct	in_addr	in, char *buf, socklen_t size);

     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);

     struct in_addr
     inet_makeaddr(in_addr_t net, in_addr_t lna);

     in_addr_t
     inet_lnaof(struct in_addr in);

     in_addr_t
     inet_netof(struct in_addr in);

DESCRIPTION
     The routines inet_aton(), inet_addr() and inet_network() interpret	char-
     acter strings representing	numbers	expressed in the Internet standard `.'
     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 was not parseable 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 *src 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).
     The size argument specifies the size, in bytes, of	the buffer *dst.
     INET_ADDRSTRLEN and INET6_ADDRSTRLEN define the maximum size required to
     convert an	address	of the respective type.	 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.	 This function is presently valid for
     AF_INET and AF_INET6.

     The routine inet_ntoa() takes an Internet address and returns an ASCII
     string representing the address in	`.' notation.  The routine
     inet_ntoa_r() is the reentrant version of inet_ntoa().  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.

     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	byte order 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.
     Note that when an Internet	address	is viewed as a 32-bit integer quantity
     on	the VAX	the bytes referred to above appear as ``d.c.b.a''.  That is,
     VAX 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 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 `.'	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; other-
     wise, the number is interpreted as	decimal).

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

ERRORS
     The inet_ntop() call fails	if:

     [ENOSPC]		size was not large enough to store the presentation
			form of	the address.

     [EAFNOSUPPORT]	*src was not an	AF_INET	or AF_INET6 family address.

SEE ALSO
     byteorder(3), getaddrinfo(3), gethostbyname(3), getnameinfo(3),
     getnetent(3), inet_net(3),	hosts(5), networks(5)

     IP	Version	6 Addressing Architecture, RFC,	2373, July 1998.

STANDARDS
     The inet_ntop() and inet_pton() functions conform to X/Open Networking
     Services Issue 5.2	(``XNS5.2'').  Note that inet_pton() does not accept
     1-, 2-, or	3-part dotted addresses; all four parts	must be	specified and
     are interpreted only as decimal values.  This is a	narrower input set
     than that accepted	by inet_aton().

HISTORY
     These functions appeared in 4.2BSD.

BUGS
     The value 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 inet_addr() function should return a struct in_addr.

FreeBSD	10.1			 June 14, 2007			  FreeBSD 10.1

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | INTERNET ADDRESSES | DIAGNOSTICS | ERRORS | SEE ALSO | STANDARDS | HISTORY | BUGS

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