#include<arpa/inet.h> int inet_pton(int family, const char *strptr, void *addrptr);返回：若成功則為1,若輸入不是有效的表達(dá)格式則為0,若出錯(cuò)則為-1 const char *inet_ntop(int family, const void *addrptr, char *strptr, size_t len);返回：若成功則為指向結(jié)果的指針， 若出錯(cuò)則為NULL

這兩個(gè)函數(shù)的family參數(shù)既可以是AF_INET，也可以是AF_INET6。如果以不被支持的地址族作為family的參數(shù)，這兩個(gè)函數(shù)就都返回一個(gè)錯(cuò)誤，并將errno置為EAFNOSUPPORT。

第一個(gè)函數(shù)嘗試轉(zhuǎn)換由strptr指針?biāo)傅淖址?#xff0c;并通過addrptr指針存放二進(jìn)制結(jié)果。若成功則返回1,否則如果對(duì)所指定的family而言輸入的字符串不是有效的表達(dá)式，那么值為0。

inet_ntop進(jìn)行相反的轉(zhuǎn)換，從數(shù)值格式（addrptr）轉(zhuǎn)換到表達(dá)格式（strptr）。len參數(shù)是目標(biāo)存儲(chǔ)單元的大小，以免該函數(shù)溢出其調(diào)用者的緩沖區(qū)。為有助于指定這個(gè)大小，在

INET_NTOP(3) Linux Programmer's Manual INET_NTOP(3)NAMEinet_ntop - convert IPv4 and IPv6 addresses from binary to text formSYNOPSIS#include <arpa/inet.h>const char *inet_ntop(int af, const void *src,char *dst, socklen_t size);DESCRIPTIONThis function converts the network address structure src in the afaddress family into a character string. The resulting string is copiedto the buffer pointed to by dst, which must be a non-null pointer. Thecaller specifies the number of bytes available in this buffer in theargument size.inet_ntop() extends the inet_ntoa(3) function to support multipleaddress families, inet_ntoa(3) is now considered to be deprecated infavor of inet_ntop(). The following address families are currentlysupported:AF_INETsrc points to a struct in_addr (in network byte order) which isconverted to an IPv4 network address in the dotted-decimal for‐mat, "ddd.ddd.ddd.ddd". The buffer dst must be at leastINET_ADDRSTRLEN bytes long.AF_INET6src points to a struct in6_addr (in network byte order) which isconverted to a representation of this address in the most appro‐priate IPv6 network address format for this address. The bufferdst must be at least INET6_ADDRSTRLEN bytes long.RETURN VALUEOn success, inet_ntop() returns a non-null pointer to dst. NULL isreturned if there was an error, with errno set to indicate the error.ERRORSEAFNOSUPPORTaf was not a valid address family.ENOSPC The converted address string would exceed the size given bysize.ATTRIBUTESFor an explanation of the terms used in this section, seeattributes(7).┌────────────┬───────────────┬────────────────┐│Interface │ Attribute │ Value │├────────────┼───────────────┼────────────────┤│inet_ntop() │ Thread safety │ MT-Safe locale │└────────────┴───────────────┴────────────────┘CONFORMING TOPOSIX.1-2001, POSIX.1-2008. Note that RFC 2553 defines a prototypewhere the last argument size is of type size_t. Many systems followRFC 2553. Glibc 2.0 and 2.1 have size_t, but 2.2 and later havesocklen_t.BUGSAF_INET6 converts IPv4-mapped IPv6 addresses into an IPv6 format.EXAMPLESee inet_pton(3).SEE ALSOgetnameinfo(3), inet(3), inet_pton(3)COLOPHONThis page is part of release 4.04 of the Linux man-pages project. Adescription of the project, information about reporting bugs, and thelatest version of this page, can be found athttp://www.kernel.org/doc/man-pages/.Linux 2015-08-08 INET_NTOP(3)INET_PTON(3) Linux Programmer's Manual INET_PTON(3)NAMEinet_pton - convert IPv4 and IPv6 addresses from text to binary formSYNOPSIS#include <arpa/inet.h>int inet_pton(int af, const char *src, void *dst);DESCRIPTIONThis function converts the character string src into a network addressstructure in the af address family, then copies the network addressstructure to dst. The af argument must be either AF_INET or AF_INET6.The following address families are currently supported:AF_INETsrc points to a character string containing an IPv4 networkaddress in dotted-decimal format, "ddd.ddd.ddd.ddd", where dddis 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_INET6src points to a character string containing an IPv6 networkaddress. The address is converted to a struct in6_addr andcopied to dst, which must be sizeof(struct in6_addr) (16) bytes(128 bits) long. The allowed formats for IPv6 addresses followthese rules:1. The preferred format is x:x:x:x:x:x:x:x. This form consistsof eight hexadecimal numbers, each of which expresses a16-bit value (i.e., each x can be up to 4 hex digits).2. A series of contiguous zero values in the preferred formatcan be abbreviated to ::. Only one instance of :: can occurin an address. For example, the loopback address0:0:0:0:0:0:0:1 can be abbreviated as ::1. The wildcardaddress, consisting of all zeros, can be written as ::.3. An alternate format is useful for expressing IPv4-mapped IPv6addresses. This form is written as x:x:x:x:x:x:d.d.d.d,where the six leading xs are hexadecimal values that definethe 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 theaddress. An example of such an address is::FFFF:204.152.189.116.See RFC 2373 for further details on the representation of IPv6addresses.RETURN VALUEinet_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. Ifaf does not contain a valid address family, -1 is returned and errno isset to EAFNOSUPPORT.ATTRIBUTESFor an explanation of the terms used in this section, seeattributes(7).┌────────────┬───────────────┬────────────────┐│Interface │ Attribute │ Value │├────────────┼───────────────┼────────────────┤│inet_pton() │ Thread safety │ MT-Safe locale │└────────────┴───────────────┴────────────────┘ CONFORMING TOPOSIX.1-2001, POSIX.1-2008.NOTESUnlike inet_aton(3) and inet_addr(3), inet_pton() supports IPv6addresses. On the other hand, inet_pton() accepts only IPv4 addressesin dotted-decimal notation, whereas inet_aton(3) and inet_addr(3) allowthe more general numbers-and-dots notation (hexadecimal and octal num‐ber formats, and formats that don't require all four bytes to beexplicitly written). For an interface that handles both IPv6addresses, and IPv4 addresses in numbers-and-dots notation, see getad‐drinfo(3).BUGSAF_INET6 does not recognize IPv4 addresses. An explicit IPv4-mappedIPv6 address must be supplied in src instead.EXAMPLEThe 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 1:0:0:0:0:0:0:81::8$ ./a.out i6 0:0:0:0:0:FFFF:204.152.189.116::ffff:204.152.189.116Program source#include <arpa/inet.h>#include <stdio.h>#include <stdlib.h>#include <string.h>intmain(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");elseperror("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 ALSOgetaddrinfo(3), inet(3), inet_ntop(3)COLOPHONThis page is part of release 4.04 of the Linux man-pages project. Adescription of the project, information about reporting bugs, and thelatest version of this page, can be found athttp://www.kernel.org/doc/man-pages/.Linux 2015-08-08 INET_PTON(3)

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