inet_ntop函数和inet_pton函数
#include这两个函数的family参数既可以是AF_INET，也可以是AF_INET6。如果以不被支持的地址族作为family的参数，这两个函数就都返回一个错误，并将errno置为EAFNOSUPPORT。
第一个函数尝试转换由strptr指针所指的字符串，并通过addrptr指针存放二进制结果。若成功则返回1,否则如果对所指定的family而言输入的字符串不是有效的表达式，那么值为0。
inet_ntop进行相反的转换，从数值格式（addrptr）转换到表达格式（strptr）。len参数是目标存储单元的大小，以免该函数溢出其调用者的缓冲区。为有助于指定这个大小，在
INET_NTOP(3) Linux Programmer's Manual INET_NTOP(3)
NAME
inet_ntop - convert IPv4 and IPv6 addresses from binary to text form
SYNOPSIS
#include
const char *inet_ntop(int af, const void *src,
char *dst, socklen_t size);
DESCRIPTION
This function converts the network address structure src in the af
address family into a character string. The resulting string is copied
to the buffer pointed to by dst, which must be a non-null pointer. The
caller specifies the number of bytes available in this buffer in the
argument size.
inet_ntop() extends the inet_ntoa(3) function to support multiple
address families, inet_ntoa(3) is now considered to be deprecated in
favor of inet_ntop(). The following address families are currently
supported:
AF_INET
src points to a struct in_addr (in network byte order) which is
converted to an IPv4 network address in the dotted-decimal for‐
mat, "ddd.ddd.ddd.ddd". The buffer dst must be at least
INET_ADDRSTRLEN bytes long.
AF_INET6
src points to a struct in6_addr (in network byte order) which is
converted to a representation of this address in the most appro‐
priate IPv6 network address format for this address. The buffer
dst must be at least INET6_ADDRSTRLEN bytes long.
RETURN VALUE
On success, inet_ntop() returns a non-null pointer to dst. NULL is
returned if there was an error, with errno set to indicate the error.
ERRORS
EAFNOSUPPORT
af was not a valid address family.
ENOSPC The converted address string would exceed the size given by
size.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
┌────────────┬───────────────┬────────────────┐
│Interface │ Attribute │ Value │
├────────────┼───────────────┼────────────────┤
│inet_ntop() │ Thread safety │ MT-Safe locale │
└────────────┴───────────────┴────────────────┘
CONFORMING TO
POSIX.1-2001, POSIX.1-2008. Note that RFC 2553 defines a prototype
where the last argument size is of type size_t. Many systems follow
RFC 2553. Glibc 2.0 and 2.1 have size_t, but 2.2 and later have
socklen_t.
BUGS
AF_INET6 converts IPv4-mapped IPv6 addresses into an IPv6 format.
EXAMPLE
See inet_pton(3).
SEE ALSO
getnameinfo(3), inet(3), inet_pton(3)
COLOPHON
This page is part of release 4.04 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
http://www.kernel.org/doc/man-pages/.
Linux 2015-08-08 INET_NTOP(3)
INET_PTON(3) Linux Programmer's Manual INET_PTON(3)
NAME
inet_pton - convert IPv4 and IPv6 addresses from text to binary form
SYNOPSIS
#include
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 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
inet_pton() 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 │
├────────────┼───────────────┼────────────────┤
│inet_pton() │ Thread safety │ MT-Safe locale │
└────────────┴───────────────┴────────────────┘
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
NOTES
Unlike inet_aton(3) and inet_addr(3), inet_pton() supports IPv6
addresses. On the other hand, inet_pton() accepts only 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 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
AF_INET6 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 inet_pton() and inet_ntop(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 in6_addr)];
int domain, s;
char str[INET6_ADDRSTRLEN];
if (argc != 3) {
fprintf(stderr, "Usage: %s {i4|i6|} 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);
}
SEE ALSO
getaddrinfo(3), inet(3), inet_ntop(3)
COLOPHON
This page is part of release 4.04 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
http://www.kernel.org/doc/man-pages/.
Linux 2015-08-08 INET_PTON(3)