前些天由于项目需要，自己整了一个比较全面的获取IP地址的函数：可以获取本地的IP地址，也可以根据域名获取IP地址，感觉比较有用特此奉献上，呵呵。

　　下面是源代码

/* GetIp.c -- Get Local or remote Ip address by domain name
* Designed by falcon, 2006-9-16, Email: zhangjinw[at]gmail.com
* */

#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <netdb.h>
#include <string.h>
#include <errno.h>
#define h_addr h_addr_list[0]

char *
GetIp(char *dn_or_ip)
{
struct sockaddr_in addr;
struct hostent *host;
struct ifreq req;
int sock;

if (dn_or_ip == NULL) return NULL;

if (strcmp(dn_or_ip, "localhost") == 0) {
sock = socket(AF_INET, SOCK_DGRAM, 0);
strncpy(req.ifr_name, "eth0", IFNAMSIZ);

if ( ioctl(sock, SIOCGIFADDR, &req) < 0 ) {
printf("ioctl error: %s\\n", strerror (errno));
return NULL;
}

dn_or_ip = (char *)inet_ntoa(*(struct in_addr *) &((struct sockaddr_in *) &req.ifr_addr)->sin_addr);
shutdown(sock, 2);
close(sock);
} else {
host = gethostbyname(dn_or_ip);
if (host == NULL) return NULL;
dn_or_ip = (char *)inet_ntoa(*(struct in_addr *)(host->h_addr));
}
return dn_or_ip;
}

　　下面是一个测试的代码
test_GetIp.c

/*test_GetIp.c*/
#include <stdio.h>
#include "GetIp.c"

int
main(int argc, char *argv[])
{
if (argc < 2) {
fprintf(stderr, "Usage: %s domain_name or ip_address\\n", argv[0]);
return -1;
}

char *current_ip_address;
current_ip_address = NULL;
if ((current_ip_address = GetIp( argv[1])) == NULL) {
printf ("Ip address convert error!\\n");
return -1;
} else {
printf("domain name or ip address : %s\\n", argv[1]);
printf("current ip address: %s\\n", current_ip_address);
}

return 0;
}

　　具体使用演示

$./test_GetIp xxxy.lzu.edu.cn --这里是根据域名转换为IP地址
domain name or ip address : xxxy.lzu.edu.cn
current ip address: 202.201.0.237

$ ./test_GetIp 219.246.79.7　--输入地址返回地址
domain name or ip address : 219.246.79.7
current ip address: 219.246.79.7

$ ./test_GetIp localhost　　--获取本地IP地址
domain name or ip address : localhost
current ip address: 219.246.79.4