获取Wi-Fi链接信号

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/wireless.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <unistd.h>
#include <arpa/inet.h>

/*
int main()
{
    FILE *fp=NULL;
    char buf[100] = {0};
    //char command[300] = "sudo iwlist wlan0 scan";
    char command[300] = "sudo iwlist wlp2s0 scan";
    char str1[100];
    char str2[100];
    char* q = NULL;
    memset(str1, '\0', sizeof(str1));
    memset(str2, '\0', sizeof(str2));
    if((fp = popen(command, "r")) != NULL)
    {
        while(fgets(buf, sizeof(buf), fp) != NULL)
        {
            q = strstr(buf, "ESSID:");
            if(q != NULL)
            {
                sscanf(q, "ESSID:\"%[^\"]", str1);
                q = NULL;
            }
            q = strstr(buf, "Signal level=");
            if(q != NULL)
            {
                sscanf(q, "Signal level=%[^/]", str2);
                printf("%s %s\n", str1,str2);
                q = NULL;
                strcat(str1, "");
                strcat(str1, str2);
                printf("%s \n", str1);
            }
        }
        pclose(fp);
    }
}
*/


#define NET_PORT 53
#define NET_IP "8.8.8.8"

int main()
{
    int sockfd;
    struct iwreq wreq;
    struct iw_statistics stats;
    char buffer[32];
    int in_len=0;
    struct sockaddr_in servaddr;
    memset(buffer, 0, 32);
    memset(&stats, 0, sizeof(stats));
    strcpy(wreq.ifr_name, "wlan0");
    //strcpy(wreq.ifr_name, "wlp2s0");

    if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
    {
        perror("Cound not create simple socket");
        return -1;
    }

    in_len = sizeof(struct sockaddr_in);
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(NET_PORT);
    servaddr.sin_addr.s_addr = inet_addr(NET_IP);

    memset(servaddr.sin_zero,0,sizeof(servaddr.sin_zero));

    if(connect(sockfd,(struct sockaddr*) &servaddr,in_len) < 0)
    {
        printf("not connect to internet!\n");
        close(sockfd);
        return -1;
    }else{
        printf("    connect ok!\n");
    }

    wreq.u.data.pointer = &stats;
    //wreq.u.data.length = sizeof(iw_statistics);
    wreq.u.data.length = sizeof(stats);
    if(ioctl(sockfd, SIOCGIWSTATS, &wreq) == -1)
    {
        perror("SIOCGIWSTATS");
        close(sockfd);
        return -2;
    }else{
        printf("Signal level%s is %d\n", (stats.qual.updated & IW_QUAL_DBM ? " (in dBm)" : ""), (signed char)stats.qual.level,(stats.qual.updated & IW_QUAL_LEVEL_UPDATED ? "(updated)" : ""));

    }

    wreq.u.essid.pointer = buffer;
    wreq.u.essid.length = 32;
    if(ioctl(sockfd, SIOCGIWESSID, &wreq) == -1){
        perror("SIOCGIWESSID");
        close(sockfd);
        return -3;
    }else{
        printf("The essid is : %s\n", wreq.u.essid.pointer);
    }

    close(sockfd);
    return 0;
}