inet_pton函数说明

NAME
       inet_pton - convert IPv4 and IPv6 addresses from text to binary form


SYNOPSIS
       #include <arpa/inet.h>


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


DESCRIPTION
       This  function converts the character string src into a network address structure in the af address family, then copies the
       network address structure to dst.  The af argument must be either AF_INET or AF_INET6.


       The following address families are currently supported:


       AF_INET
              src points to a character string containing an IPv4 network address  in  dotted-decimal  format,  "ddd.ddd.ddd.ddd",
              where  ddd  is  a  decimal number of up to three digits in the range 0 to 255.  The address is converted to a struct
              in_addr and copied to dst, which must be sizeof(struct in_addr) (4) bytes (32 bits) long.


       AF_INET6
              src points to a character string containing an IPv6 network address.  The address is converted to a struct  in6_addr
              and  copied  to dst, which must be sizeof(struct in6_addr) (16) bytes (128 bits) long.  The allowed formats for IPv6
              addresses follow these rules:


              1. The preferred format is x:x:x:x:x:x:x:x.  This  form  consists  of  eight  hexadecimal  numbers,  each  of  which
                 expresses a 16-bit value (i.e., each x can be up to 4 hex digits).


              2. A series of contiguous zero values in the preferred format can be abbreviated to ::.  Only one instance of :: can
                 occur in an address.  For example, the loopback address 0:0:0:0:0:0:0:1 can be abbreviated as ::1.  The  wildcard
                 address, consisting of all zeros, can be written as ::.


              3. An   alternate   format  is  useful  for  expressing  IPv4-mapped  IPv6  addresses.   This  form  is  written  as
                 x:x:x:x:x:x:d.d.d.d, where the six leading xs are hexadecimal values that define the six most-significant  16-bit
                 pieces  of  the  address  (i.e., 96 bits), and the ds express a value in dotted-decimal notation that defines the
                 least significant 32 bits of the address.  An example of such an address is ::FFFF:204.152.189.116.

              See RFC 2373 for further details on the representation of IPv6 addresses.

RETURN VALUE
       inet_pton() returns 1 on success (network address was successfully converted).  0 is returned if src  does  not  contain  a
       character  string  representing  a  valid  network address in the specified address family.  If af does not contain a valid
       address family, -1 is returned and errno is set to EAFNOSUPPORT.


CONFORMING TO
       POSIX.1-2001.


NOTES
       Unlike inet_aton(3) and inet_addr(3), inet_pton() supports IPv6 addresses.  On the other  hand,  inet_pton()  only  accepts
       IPv4  addresses  in  dotted-decimal notation, whereas inet_aton(3) and inet_addr(3) allow the more general numbers-and-dots
       notation (hexadecimal and octal number formats, and formats that don't require all four bytes to  be  explicitly  written).
       For an interface that handles both IPv6 addresses, and IPv4 addresses in numbers-and-dots notation, see getaddrinfo(3).


BUGS
       AF_INET6 does not recognize IPv4 addresses.  An explicit IPv4-mapped IPv6 address must be supplied in src instead.

      #include <arpa/inet.h>       #include <stdio.h>       #include <stdlib.h>       #include <string.h>       int       main(int argc, char *argv[])       {           unsigned char buf[sizeof(struct in6_addr)];           int domain, s;           char str[INET6_ADDRSTRLEN];           if (argc != 3) {               fprintf(stderr, "Usage: %s {i4|i6|<num>} string\n", argv[0]);               exit(EXIT_FAILURE);           }           domain = (strcmp(argv[1], "i4") == 0) ? AF_INET :                    (strcmp(argv[1], "i6") == 0) ? AF_INET6 : atoi(argv[1]);           s = inet_pton(domain, argv[2], buf);           if (s <= 0) {               if (s == 0)                   fprintf(stderr, "Not in presentation format");               else                   perror("inet_pton");               exit(EXIT_FAILURE);           }           if (inet_ntop(domain, buf, str, INET6_ADDRSTRLEN) == NULL) {               perror("inet_ntop");               exit(EXIT_FAILURE);           }           printf("%s\n", str);           exit(EXIT_SUCCESS);       }