ubuntu1804 搜索wifi的C程序

以下是一个简单的C程序，可以在Ubuntu 18.04上搜索可用的WiFi网络：

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

int main() {
    int sockfd;
    struct iwreq req;
    char buffer[1024];

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    if(sockfd < 0) {
        perror("Socket error");
        return 1;
    }

    strncpy(req.ifr_name, "wlan0", IFNAMSIZ);

    if(ioctl(sockfd, SIOCGIWNAME, &req) == -1) {
        perror("Wireless interface not found");
        close(sockfd);
        return 1;
    }

    if(ioctl(sockfd, SIOCGIWSCAN, &req) == -1) {
        perror("Scan failed");
        close(sockfd);
        return 1;
    }

    struct iw_scan_req scan_req;
    memset(&scan_req, 0, sizeof(scan_req));
    strncpy(scan_req.ifname, "wlan0", IFNAMSIZ);
    scan_req.scan_type = IW_SCAN_TYPE_PASSIVE;
    scan_req.scan_flags = 0;

    req.u.data.pointer = (caddr_t) &scan_req;
    req.u.data.length = sizeof(scan_req);
    req.u.data.flags = 0;

    if(ioctl(sockfd, SIOCSIWSCAN, &req) == -1) {
        perror("Scan request failed");
        close(sockfd);
        return 1;
    }

    sleep(5);

    req.u.data.pointer = buffer;
    req.u.data.length = sizeof(buffer);
    req.u.data.flags = 0;

    if(ioctl(sockfd, SIOCGIWSCAN, &req) == -1) {
        perror("Failed to get scan results");
        close(sockfd);
        return 1;
    }

    struct iw_event iwe;
    struct iw_scan_ap_info ap_info;
    char ssid[IW_ESSID_MAX_SIZE + 1];

    memcpy(&iwe, buffer, sizeof(iwe));

    while(iwe.cmd != SIOCGIWSCAN) {
        if(iwe.cmd == SIOCGIWAP) {
            memcpy(&ap_info, &iwe.u.ap_info, sizeof(ap_info));
        } else if(iwe.cmd == SIOCGIWFREQ) {
            printf("SSID: %s\n", ssid);
            printf("Frequency: %d MHz\n", iwe.u.freq.m);
        } else if(iwe.cmd == SIOCGIWESSID) {
            memcpy(ssid, iwe.u.essid.pointer, iwe.u.essid.length);
            ssid[iwe.u.essid.length] = '\0';
        }

        memcpy(&iwe, ((char *) &iwe) + iwe.len, sizeof(iwe));
    }

    close(sockfd);

    return 0;
}

请注意，此程序需要在root权限下运行