如何打印hostent结构体中的所有数据

来源：互联网发布：魔兽7.0数据库dps 编辑：程序博客网时间：2024/05/21 17:12

问题：

hostent是gethostbyname()和gethostbyaddr()都会涉及到的一个结构体。代码如下：

struct hostent {
char *h_name;
char **h_aliases;
int h_addrtype;
int h_length;
char **h_addr_list;
};

gethostbyname()的原型是：

struct hostent *gethostbyname(const char *name);
函数的传入值是域名或者主机名，例如"www.google.com"、"191.168.1.253"等；
函数的返回值：

成功时，返回一个指向hostent结构的指针；

失败时，返回NULL。

编程调试过程中需要查看所取到的IP地址等信息，所以将hostent的全部内容打印出来就对调试很有帮助了。

解决办法：

#include <stdio.h>#include <stdlib.h>#include <netdb.h>#include <sys/socket.h>int main(int argc, char *argv[]){char *ptr,**pptr;struct hostent *host;char str[32];char *hostname;if (argc < 2) {fprintf(stderr, "USAGE: ./pri-hostent Hostname(of ip addr such as 192.168.1.101)\n");exit(1);}/* get the host name */hostname = argv[1];// if ((host = (struct hostent*)gethostbyname(argv[1])) == NULL) {if ((host = (struct hostent*)gethostbyname(hostname)) == NULL) {perror("gethostbyname");return(1);}printf("Host name is: %s\n", host->h_name);/* printf all the aliases of host */for(pptr = host->h_aliases; *pptr != NULL; pptr++) {printf("  alias of host: %s\n",*pptr);}printf("Host addrtype is: %d\n", host->h_addrtype);printf("Host length is: %d\n", host->h_length);// // printf("Host is: %x\n", *((struct in_addr*)host->h_addr));/* printf ip address according to addrtype */switch(host->h_addrtype) {case AF_INET:case AF_INET6:pptr = host->h_addr_list;/* print all the aliases,inet_ntop() is called */for(; *pptr!=NULL; pptr++) {inet_ntop(host->h_addrtype, *pptr, str, sizeof(str));printf("  address: %s\n", str);}break;default:printf("unknown address type\n");break;}return 0;}

程序的运行结果：

dingq@wd-u1110:~/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket$ ./pri-hostent USAGE: ./pri-hostent Hostname(of ip addr such as 192.168.1.101)dingq@wd-u1110:~/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket$ ./pri-hostent www.google.comHost name is: www.l.google.com  alias of host: www.google.comHost addrtype is: 2Host length is: 4  address: 74.125.128.106  address: 74.125.128.147  address: 74.125.128.99  address: 74.125.128.103  address: 74.125.128.104  address: 74.125.128.105