Linux上C/C++怎样通过主机名获得IP

Linux下C/C++怎样通过主机名获得IP?
各位高手：
  求getaddrbyhost()函数使用例子，求下面这个代码反过来的，通过主机名获得IP：

C/C++ code

#include <stdio.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <netdb.h>int main(int argc, char **argv){        struct hostent *ip;        unsigned long hostname;        if (argc != 2)        {                printf("Need to specify an IP address.\n");                return -1;        }        if ((hostname = inet_addr(argv[1])) == -1)        {                printf("Could not find %s\n", argv[1]);                return -1;        }        else        {                printf("hostname : %ld\n", hostname);        }        if ((ip = gethostbyaddr((char *)&hostname, sizeof(long), AF_INET)) != NULL)                printf("%s is %s\n", argv[1], ip->h_name);        else                printf("Could not resolve %s\n", argv[1]);        return 0;}

[解决办法]

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各位高手：
求getaddrbyhost()函数使用例子，求下面这个代码反过来的，通过主机名获得IP：
C/C++ code

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

[解决办法]
struct hostent *gethostbyname(const char *name);

#include <sys/socket.h> /* for AF_INET */
struct hostent *gethostbyaddr(const void *addr,
socklen_t len, int type);


这些都是淘汰的函数了，只支持IPV4。

C/C++ code

SYNOPSIS       #include <sys/types.h>       #include <sys/socket.h>       #include <netdb.h>       int getaddrinfo(const char *node, const char *service,                       const struct addrinfo *hints,                       struct addrinfo **res);       void freeaddrinfo(struct addrinfo *res);       const char *gai_strerror(int errcode);   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):       getaddrinfo(), freeaddrinfo(), gai_strerror():           _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCEDESCRIPTION       Given  node and service, which identify an Internet host and a service, getaddrinfo() returns one or more addrinfo structures, each of which contains an       Internet address that can be specified in a call to bind(2) or connect(2).  The getaddrinfo() function combines the functionality provided by  the  get-       servbyname(3) and getservbyport(3) functions into a single interface, but unlike the latter functions, getaddrinfo() is reentrant and allows programs to       eliminate IPv4-versus-IPv6 dependencies.       The addrinfo structure used by getaddrinfo() contains the following fields:           struct addrinfo {               int              ai_flags;               int              ai_family;               int              ai_socktype;               int              ai_protocol;               size_t           ai_addrlen;               struct sockaddr *ai_addr;               char            *ai_canonname;               struct addrinfo *ai_next;           };