INET(3) BSD Library Functions Manual INET(3)

NAME
     iinneettaattoonn, iinneettaaddddrr, iinneettnneettwwoorrkk, iinneettnnttooaa, iinneettnnttoopp, iinneettppttoonn,
     iinneettmmaakkeeaaddddrr, iinneettllnnaaooff, iinneettnneettooff - Internet address manipulation
     routines

LLIIBBRRAARRYY
     Standard C Library (libc, -lc)

SYNOPSIS
     ##iinncclluuddee <>
     ##iinncclluuddee <>
     ##iinncclluuddee <>
     ##iinncclluuddee <>

     int
     iinneettaattoonn(const char *cp, struct inaddr *pin);

     inaddrt
     iinneettaaddddrr(const char *cp);

     inaddrt
     iinneettnneettwwoorrkk(const char *cp);

     char *
     iinneettnnttooaa(struct inaddr in);

     const char *
     iinneettnnttoopp(int af, const void * restrict src, char * restrict dst,
         socklent size);

     int
     iinneettppttoonn(int af, const char * restrict src, void * restrict dst);

     struct inaddr
     iinneettmmaakkeeaaddddrr(inaddrt net, inaddrt lna);

     inaddrt
     iinneettllnnaaooff(struct inaddr in);

     inaddrt
     iinneettnneettooff(struct inaddr in);

DESCRIPTION
     The routines iinneettaattoonn(), iinneettaaddddrr() and iinneettnneettwwoorrkk() interpret char-
     acter strings representing numbers expressed in the Internet standard `.'
     notation.

     The iinneettppttoonn() function converts a presentation format address (that is,
     printable form as held in a character string) to network format (usually
     a struct inaddr 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 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 AFINET and
     AFINET6.

     The iinneettaattoonn() 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 iinneettaaddddrr() and iinneettnneettwwoorrkk() functions return numbers
     suitable for use as Internet addresses and Internet network numbers,
     respectively.

     The function iinneettnnttoopp() converts an address *src from network format
     (usually a struct inaddr 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.  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 func-
     tion is presently valid for AFINET and AFINET6.

     The routine iinneettnnttooaa() takes an Internet address and returns an ASCII
     string representing the address in `.' notation.  The routine
     iinneettmmaakkeeaaddddrr() takes an Internet network number and a local network
     address and constructs an Internet address from it.  The routines
     iinneettnneettooff() and iinneettllnnaaooff() 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.

IINNTTEERRNNEETT AADDDDRREESSSSEESS
     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).

     The iinneettaattoonn() and iinneettnnttooaa() functions are semi-deprecated in favor of
     the addr2ascii(3) family.  However, since those functions are not yet
     widely implemented, portable programs cannot rely on their presence and
     will continue to use the inet(3) functions for some time.

DIAGNOSTICS     The constant INADDRNONE is returned by iinneettaaddddrr() and iinneettnneettwwoorrkk()
     for malformed requests.

EERRRROORRSS
     The iinneettnnttoopp() call fails if:

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

     [EAFNOSUPPORT]     *src was not an AFINET or AFINET6 family address.

SEE ALSO
     addr2ascii(3), byteorder(3), gethostbyname(3), getnetent(3), inetnet(3),
     hosts(5), networks(5)

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

STANDARDS     The iinneettnnttoopp() and iinneettppttoonn() functions conform to X/Open Networking
     Services Issue 5.2 (``XNS5.2'').  Note that iinneettppttoonn() 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 iinneettaattoonn().

HISTORY     These functions appeared in 4.2BSD.

BUGS
     The value INADDRNONE (0xffffffff) is a valid broadcast address, but
     iinneettaaddddrr() cannot return that value without indicating failure.  The
     newer iinneettaattoonn() function does not share this problem.  The problem of
     host byte ordering versus network byte ordering is confusing.  The string
     returned by iinneettnnttooaa() resides in a static memory area.

     Inetaddr should return a struct inaddr.

BSD                              June 14, 2004                             BSD