NAME    [Toc]    [Back]

     inet_net_ntop, inet_net_pton -- Internet network number manipulation routines

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

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

     char *
     inet_net_ntop(int af, const void *src, int bits, char *dst, size_t size);

     int
     inet_net_pton(int af, const char *src, void *dst, size_t size);

DESCRIPTION    [Toc]    [Back]

     The inet_net_ntop() function converts an Internet network number from
     network format (usually a struct in_addr or some other binary form, in
     network byte order) to CIDR presentation format (suitable for external
     display purposes).  The bits argument is the number of bits in src that
     are the network number.  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 inet_net_pton() function converts a presentation format Internet network
 number (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 the number of bits
     (either computed based on the class, or specified with /CIDR), or -1 if a
     failure occurred (in which case errno will have been set.	It will be set
     to ENOENT if the Internet network number was not valid).

     The only value for af currently supported is AF_INET.  The size argument
     is the size of the result buffer dst.

NETWORK NUMBERS (IP VERSION 4)    [Toc]    [Back]

     Internet network numbers may be specified in one of the following forms:

	   a.b.c.d/bits
	   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 network
     number.  Note that when an Internet network number is viewed as a 32-bit
     integer quantity on a system that uses little-endian byte order (such as
     the Intel 386, 486, 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 number is specified, the last part is interpreted as a
     16-bit quantity and placed in the rightmost two bytes of the Internet
     network number.  This makes the three part number format convenient for
     specifying Class B network numbers as ``128.net.host''.

     When a two part number is supplied, the last part is interpreted as a
     24-bit quantity and placed in the rightmost three bytes of the Internet
     network number.  This makes the two part number format convenient for
     specifying Class A network numbers as ``net.host''.

     When only one part is given, the value is stored directly in the Internet
     network number 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; otherwise,
 the number is interpreted as decimal).

SEE ALSO    [Toc]    [Back]

     byteorder(3), inet(3), networks(5)

HISTORY    [Toc]    [Back]

     The inet_net_ntop() and inet_net_pton() functions appeared in BIND 4.9.4.


FreeBSD 5.2.1			 June 18, 1997			 FreeBSD 5.2.1