LINUX

Linux编程获取本机IP地址的几种方法

参考：

https://blog.csdn.net/zhongmushu/article/details/89944990

https://www.cnblogs.com/lzpong/p/6956439.html

在进行Linux网络编程时，经常会需要获取本机IP地址，除了常规的读取配置文件外，本文罗列几种个人所知的编程常用方法，仅供参考，如有错误请指出。

方法一：使用ioctl()获取本地IP地址 

Linux下可以使用ioctl()函数以及结构体 struct ifreq和结构体struct ifconf来获取网络接口的各种信息。具体过程是先通过ictol获取本地所有接口的信息保存到ifconf结构中，再从其中取出每个ifreq表示的接口信息。

如果本机的IP地址绑定在第一块网卡上，则只需指定网卡名称，无需获取所有网卡的信息即可获取，见如下函数：

int get_localip(const char * eth_name, char *local_ip_addr)
{
int ret = -1;
register int fd;
struct ifreq ifr;

if (local_ip_addr == NULL || eth_name == NULL)
{
return ret;
}
if ((fd=socket(AF_INET, SOCK_DGRAM, 0)) > 0)
{
strcpy(ifr.ifr_name, eth_name);
if (!(ioctl(fd, SIOCGIFADDR, &ifr)))
{
ret = 0;
strcpy(local_ip_addr, inet_ntoa(((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr));
}
}
if (fd > 0)
{
close(fd);
}
return ret;
}

如果想通过获取所有网络接口信息，示例代码如下：

#include <stdio.h>
#include <net/if.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <netinet/in.h>

int get_localip(const char * eth_name, char *local_ip_addr)
{
int ret = -1;
register int fd, intrface;
struct ifreq ifr[32];
struct ifconf ifc;

if (local_ip_addr == NULL || eth_name == NULL)
{
return ret;
}
if ((fd=socket(AF_INET, SOCK_DGRAM, 0)) > 0)
{
ifc.ifc_len = sizeof ifr;
ifc.ifc_buf = (caddr_t)ifr;
if (!ioctl(fd, SIOCGIFCONF, (char*)&ifc)) //获取所有接口信息
{
intrface = ifc.ifc_len / sizeof(struct ifreq);
while (intrface-- > 0)
{
//Get IP Address
if (!(ioctl(fd, SIOCGIFADDR, (char*)&ifr[intrface])))
{
if(strcmp(eth_name, ifr[intrface].ifr_name) == 0)
{
ret = 0;
sprintf(local_ip_addr, "%s", inet_ntoa(((struct sockaddr_in*)(&ifr[intrface].ifr_addr))->sin_addr));
break;
}
}
}
}
}
if (fd > 0)
{
close(fd);
}
return ret;
}

int main(int argc, const char **argv)
{
int ret;
char local_ip[20] = {0};

ret = get_localip("eth0", local_ip);
if (ret == 0)
{
printf("local ip:%s
", local_ip);
}
else
{
printf("get local ip failure
");
}
return 0;
}

方法二：getsockname()获取本地IP地址 

getsockname()用于获取一个已捆绑或已连接套接字的本地地址。若一个套接字与INADDR_ANY捆绑，也就是说该套接字可以用任意主机的地址，此时除非调用connect()或accept()来连接，否则getsockname()将不会返回主机IP地址的任何信息。

示例代码：

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define PORT 80
#define SERVER_IP "14.215.177.38"

int main(int argc, const char **argv)
{
int ret = -1;
socklen_t len;
char buf[30] = {0};
struct sockaddr_in server_addr, local_addr;
int fd = socket(AF_INET, SOCK_STREAM, 0);
//int fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd <= 0)
{
printf("fail to creat socket
");
return -1;
}

memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(PORT);
server_addr.sin_addr.s_addr = inet_addr(SERVER_IP);
if(connect(fd, (struct sockaddr*)&server_addr, sizeof(server_addr))<0)
{
printf("connect error!!!
");
goto end;
}
len = sizeof(local_addr);
memset(&local_addr, 0, sizeof(local_addr));
ret = getsockname(fd, (struct sockaddr*)&local_addr, &len);
if (ret == 0)
{
printf("local ip is %s, local port is %d
", inet_ntop(AF_INET, &local_addr.sin_addr, buf, sizeof(buf)), ntohs(local_addr.sin_port));
}
else
{
printf("getsockname failed, error=%d
", errno);
}

end:
if (fd)
{
close(fd);
}
return ret;
}

方法三：getaddrinfo()获取本地IP地址

getaddrinfo()可以完成网络主机中主机名和服务名到地址的映射，但是一般不能用来获取本地IP地址，当它用来获取本地IP地址时，返回的一般是127.0.0.1本地回环地址，且该函数仅仅支持IPv4。

示例代码：

#include <netdb.h>
#include <stdio.h>
#include <unistd.h>
#include <arpa/inet.h>

// 获取本地IP时，一般都是127.0.0.1
int main(int argc, const char **argv)
{
int ret;
char host_name[128] = {0};
struct addrinfo *res, *cur;
struct sockaddr_in *addr;

if (gethostname(host_name, sizeof(host_name)) < 0)
{
printf("gethostname error
");
return -1;
}
ret = getaddrinfo(host_name, NULL, NULL, &res);
if (ret != 0)
{
printf("Error: error in getaddrinfo on hostname: %s
", gai_strerror(ret));
return -1;
}
for(cur = res; cur != NULL; cur = cur->ai_next)
{
if(cur->ai_family == AF_INET)
{
addr = (struct sockaddr_in*)cur->ai_addr;
printf("local ip:%s
", inet_ntoa(addr->sin_addr));
}
//char host[1024] = {0};
//ret = getnameinfo(cur->ai_addr, cur->ai_addrlen, host, sizeof(host), NULL, 0, NI_NUMERICHOST);
//if(ret != 0)
//{
//    printf("getnameinfo: %s
", gai_strerror(ret));
//}
//else
//{
//    printf("ip: %s
", host);
//}
}
freeaddrinfo(res);
return 0;
}

方法四：gethostbyname ()获取本地IP地址

gethostbyname()和getaddrinfo()的功能类似，一般用于通过主机名或者服务名，比如域名来获取主机的IP地址。但是要想获取本地IP地址的时候，一般获取的是回环地址127.0.0.1。

示例代码：

#include <netdb.h>
#include <stdio.h>
#include <unistd.h>
#include <arpa/inet.h>

// 获取本地IP时，一般都是127.0.0.1
int main(int argc, const char **argv)
{
int i = 0;
char host_name[128] = {0};
struct hostent *hptr;

if (gethostname(host_name, sizeof(host_name)) < 0)
{
printf("gethostname error
");
return -1;
}
if ((hptr=gethostbyname(host_name)) == NULL)
{
printf("gethostbyname error
");
return -1;
}
while(hptr->h_addr_list[i] != NULL)
{
printf("hostname: %s
", hptr->h_name);
printf(" ip: %s
", inet_ntoa(*(struct in_addr*)hptr->h_addr_list[i]));
i++;
}
return 0;
}

方法五：通过getifaddrs()获取本地IP地址

/*代码来自StackOverflow:

http://stackoverflow.com/questions/212528/linux-c-get-the-ip-address-of-local-computer */

示例代码：

#include <stdio.h>
#include <sys/types.h>
#include <ifaddrs.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>

int main (int argc, const char * argv[])
{
struct ifaddrs * ifAddrStruct=NULL;
struct ifaddrs * ifa=NULL;
void * tmpAddrPtr=NULL;

getifaddrs(&ifAddrStruct);

for (ifa = ifAddrStruct; ifa != NULL; ifa = ifa->ifa_next)
{
if (!ifa->ifa_addr)
{
continue;
}
if (ifa->ifa_addr->sa_family == AF_INET) // check it is IP4
{
// is a valid IP4 Address
tmpAddrPtr=&((struct sockaddr_in *)ifa->ifa_addr)->sin_addr;
char addressBuffer[INET_ADDRSTRLEN];
inet_ntop(AF_INET, tmpAddrPtr, addressBuffer, INET_ADDRSTRLEN);
printf("%s IP Address %s
", ifa->ifa_name, addressBuffer);
}
else if (ifa->ifa_addr->sa_family == AF_INET6) // check it is IP6
{
// is a valid IP6 Address
tmpAddrPtr=&((struct sockaddr_in6 *)ifa->ifa_addr)->sin6_addr;
char addressBuffer[INET6_ADDRSTRLEN];
inet_ntop(AF_INET6, tmpAddrPtr, addressBuffer, INET6_ADDRSTRLEN);
printf("%s IP Address %s
", ifa->ifa_name, addressBuffer);
}
}
if (ifAddrStruct!=NULL)
{
freeifaddrs(ifAddrStruct);
}

return 0;
}

方法六：通过popen()调用ifconfig获取本地IP地址

用popen()建立一个管道，管道的一端执行命令ifconfig，管道的另一端读取收到的数据并进行相应的解析。这种方法需要执行shell命令，配合正则表达式，效率较低，一般不采用。而这种方式其实更倾向于配置，原因就是使用简单。

示例代码：

#include <stdio.h>
#include <stdlib.h>

#define ETH_NAME    "ens33"

int main(int argc, const char *argv[])
{
FILE *fp;
char buf[256] = {0};
char command[256] = {0};
//char *fmt = "ifconfig %s|sed -n '2p'|sed -n 's#^.*dr:##gp'|sed -n 's#B.*$##gp'";
char *fmt = "ifconfig %s|grep 'inet addr'|awk '{ print $2}' | awk -F: '{print $2}'";

snprintf(command, sizeof(command), fmt, ETH_NAME);
if((fp = popen(command, "r")) == NULL)
{
perror("Fail to popen
");
return -1;
}
while(fgets(buf, sizeof(buf), fp) != NULL)
{
printf("%s", buf);
}

pclose(fp);
return 0;
}

方法七：获取所有ip（ipv4+ipv6）

//#include <sys/types.h>
#include <ifaddrs.h>
#include <sys/ioctl.h> 
#include <net/if.h> 
#include <string.h> 
#include <stdio.h>
#include <unistd.h>
#include <netdb.h>
//#include <sys/socket.h>
//#include <netinet/in.h>
#include <arpa/inet.h>
void pHx(unsigned char* p,int len){
  printf("Hex: ");
  for(int i=0;i<len;i++){
    printf("%02X:",p[i]);
  }
  printf("
");
}
char* getMac(char* mac,char* dv){
    struct   ifreq   ifreq; 
    int   sock; 
    if(!mac || !dv)
        return mac;
    if((sock=socket(AF_INET,SOCK_STREAM,0)) <0) 
    { 
        perror( "socket "); 
        return mac; 
    } 
    strcpy(ifreq.ifr_name,dv); 
    if(ioctl(sock,SIOCGIFHWADDR,&ifreq) <0) 
    { 
        perror( "ioctl "); 
        return mac; 
    }
    pHx((unsigned char*)ifreq.ifr_hwaddr.sa_data,sizeof(ifreq.ifr_hwaddr.sa_data));
    sprintf(mac, "%02X:%02X:%02X:%02X:%02X:%02X", //以太网MAC地址的长度是48位
           (unsigned char)ifreq.ifr_hwaddr.sa_data[0], 
           (unsigned char)ifreq.ifr_hwaddr.sa_data[1], 
           (unsigned char)ifreq.ifr_hwaddr.sa_data[2], 
           (unsigned char)ifreq.ifr_hwaddr.sa_data[3], 
           (unsigned char)ifreq.ifr_hwaddr.sa_data[4], 
           (unsigned char)ifreq.ifr_hwaddr.sa_data[5]);
    return mac;
}

int main (int argc, const char * argv[])
{
    char hname[128];
    struct hostent *hent;
    int i;

    gethostname(hname, sizeof(hname));

    //hent = gethostent();
    hent = gethostbyname(hname);

    printf("hostname: %s
", hent->h_name);
//----------------------------------------------------------
    printf("

");

    char mac[30];
    struct ifaddrs * ifap0=NULL,*ifap=NULL;
    void * tmpAddrPtr=NULL;

    getifaddrs(&ifap0);
    ifap=ifap0;
    while (ifap!=NULL) {
        if (ifap->ifa_addr->sa_family==AF_INET) { // check it is IP4
            // is a valid IP4 Address
            tmpAddrPtr=&((struct sockaddr_in *)ifap->ifa_addr)->sin_addr;
            char addressBuffer[INET_ADDRSTRLEN];
            inet_ntop(AF_INET, tmpAddrPtr, addressBuffer, INET_ADDRSTRLEN);
            if(strcmp(addressBuffer,"127.0.0.1")!=0){
            printf("%s IPv4: %s
", ifap->ifa_name, addressBuffer);
            printf("MAC: %s

",getMac(mac,ifap->ifa_name));
            }
        } else if (ifap->ifa_addr->sa_family==AF_INET6) { // check it is IP6
            // is a valid IP6 Address
            tmpAddrPtr=&((struct sockaddr_in *)ifap->ifa_addr)->sin_addr;
            char addressBuffer[INET6_ADDRSTRLEN];
            inet_ntop(AF_INET6, tmpAddrPtr, addressBuffer, INET6_ADDRSTRLEN);
            if(strcmp(addressBuffer,"::")!=0){
                printf("%s IPv6: %s
", ifap->ifa_name, addressBuffer); 
                printf("MAC: %s

",getMac(mac,ifap->ifa_name));
            }
        }
        ifap=ifap->ifa_next;
    }
    if (ifap0) { freeifaddrs(ifap0); ifap0 = NULL; }
    return 0;
}

参考文献

[1]https://blog.csdn.net/bailyzheng/article/details/7489656

[2]https://blog.csdn.net/k346k346/article/details/48231933

原文链接：https://blog.csdn.net/zhongmushu/article/details/89944990