INETPTON(3) Linux Programmer's Manual INETPTON(3)

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

SYNOPSIS
       #include 

       int inetpton(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 AFINET or AFINET6.

       The following address families are currently supported:

       AFINET
              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 inaddr and copied to  dst,
              which must be sizeof(struct inaddr) (4) bytes (32 bits) long.

       AFINET6
              src  points  to  a  character  string containing an IPv6 network
              address.  The address is converted  to  a  struct  in6addr  and
              copied  to dst, which must be sizeof(struct in6addr) (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 nota‐
                 tion 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
       inetpton() returns 1 on success (network address was successfully con‐
       verted).  0 is returned if src does not contain a character string rep‐
       resenting  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.

ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       ┌────────────┬───────────────┬────────────────┐
       │Interface   │ Attribute     │ Value          │
       ├────────────┼───────────────┼────────────────┤
       │inetpton() │ Thread safety │ MT-Safe locale │
       └────────────┴───────────────┴────────────────┘
CONFORMING TO
       POSIX.1-2001.

NOTES
       Unlike  inetaton(3)  and  inetaddr(3),  inetpton()   supports   IPv6
       addresses.   On the other hand, inetpton() accepts only IPv4 addresses
       in dotted-decimal notation, whereas inetaton(3) and inetaddr(3) allow
       the  more general numbers-and-dots notation (hexadecimal and octal num‐
       ber 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  getad‐
       drinfo(3).

BUGS
       AFINET6  does  not  recognize IPv4 addresses.  An explicit IPv4-mapped
       IPv6 address must be supplied in src instead.

EXAMPLE
       The program below demonstrates the use of inetpton() and inetntop(3).
       Here are some example runs:

           $ ./a.out i6 0:0:0:0:0:0:0:0
           ::
           $ ./a.out i6 1:0:0:0:0:0:0:8
           1::8
           $ ./a.out i6 0:0:0:0:0:FFFF:204.152.189.116
           ::ffff:204.152.189.116

   Program source

       #include 
       #include 
       #include 
       #include 

       int
       main(int argc, char *argv[])
       {
           unsigned char buf[sizeof(struct in6addr)];
           int domain, s;
           char str[INET6ADDRSTRLEN];

           if (argc != 3) {
               fprintf(stderr, "Usage: %s {i4|i6|} string\n", argv[0]);
               exit(EXITFAILURE);
           }

           domain = (strcmp(argv[1], "i4") == 0) ? AFINET :
                    (strcmp(argv[1], "i6") == 0) ? AFINET6 : atoi(argv[1]);

           s = inetpton(domain, argv[2], buf);
           if (s <= 0) {
               if (s == 0)
                   fprintf(stderr, "Not in presentation format");
               else
                   perror("inetpton");
               exit(EXITFAILURE);
           }

           if (inetntop(domain, buf, str, INET6ADDRSTRLEN) == NULL) {
               perror("inetntop");
               exit(EXITFAILURE);
           }

           printf("%s\n", str);

           exit(EXITSUCCESS);
       }

SEE ALSO
       getaddrinfo(3), inet(3), inetntop(3)

COLOPHON
       This  page  is  part of release 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-06-18                      INETPTON(3)