linux 下获取当前网络连接状态的两种方法

 

#include <sys/socket.h>#include <sys/ioctl.h>#include <linux/if.h>#include <string.h>#include <stdio.h>#include <stdlib.h>#include <unistd.h>#define ETHTOOL_GLINK        0x0000000a /* Get link status (ethtool_value) */typedef enum { IFSTATUS_UP, IFSTATUS_DOWN, IFSTATUS_ERR } interface_status_t;typedef signed int u32;/* for passing single values */struct ethtool_value{    u32    cmd;    u32    data;};interface_status_t interface_detect_beat_ethtool(int fd, char *iface){    struct ifreq ifr;    struct ethtool_value edata;       memset(&ifr, 0, sizeof(ifr));    strncpy(ifr.ifr_name, iface, sizeof(ifr.ifr_name)-1);    edata.cmd = ETHTOOL_GLINK;    ifr.ifr_data = (caddr_t) &edata;    if (ioctl(fd, SIOCETHTOOL, &ifr) == -1)    {        perror("ETHTOOL_GLINK failed ");        return IFSTATUS_ERR;    }    return edata.data ? IFSTATUS_UP : IFSTATUS_DOWN;}int main (int argc, char *argv[]){    FILE *fp;    interface_status_t status;    char buf[512] = {'\0'};    char hw_name[10] = {'\0'};    char *token = NULL;    /* 获取网卡名称 */    if ((fp = fopen("/proc/net/dev", "r")) != NULL)    {        while (fgets(buf, sizeof(buf), fp) != NULL)        {            if(strstr(buf, "eth") != NULL)            {                       token = strtok(buf, ":");                while (*token == ' ') ++token;                strncpy(hw_name, token, strlen(token));            }        }    }    fclose(fp);//方法一：查看一个文件文件，相对来说比较简单#if 1    char carrier_path[512] = {'\0'};        memset(buf, 0, sizeof(buf));     snprintf(carrier_path, sizeof(carrier_path), "/sys/class/net/%s/carrier", hw_name);    if ((fp = fopen(carrier_path, "r")) != NULL)    {        while (fgets(buf, sizeof(buf), fp) != NULL)        {            if (buf[0] == '0')            {                status = IFSTATUS_DOWN;            }            else            {                status = IFSTATUS_UP;            }        }    }    else    {        perror("Open carrier ");    }    fclose(fp);#endif//方法二：用函数吧！有点复杂，但是也是一种有效的办法#if 1    int fd;        if((fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)    {        perror("socket ");        exit(0);    }    status = interface_detect_beat_ethtool(fd, hw_name);    close(fd);#endif    switch (status)    {        case IFSTATUS_UP:            printf("%s : link up\n", hw_name);            break;                case IFSTATUS_DOWN:            printf("%s : link down\n", hw_name);            break;                default:            printf("Detect Error\n");            break;    }    return 0;}