c - 想在UBUNTU中通过C++了解无线网络的ESSID

Question

我编写了以下程序来获取我的桌面当前连接到的无线网络的 ESSID，但它给我错误。谁能帮我改正错误？代码:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/types.h> 
#include <fcntl.h>
#include <errno.h>
#include <linux/wireless.h>

#define IW_INTERFACE "wlan0"

extern int errno;
struct iwreq wreq;

int main (void)
{
    int sockfd;
    char * id;

    memset(&wreq, 0, sizeof(struct iwreq));
    sprintf(wreq.ifr_name, IW_INTERFACE);

    if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        fprintf(stderr, "Cannot open socket \n");
        fprintf(stderr, "errno = %d \n", errno);
        fprintf(stderr, "Error description is : %s\n",strerror(errno));
        exit(1);
    }
    printf("Socket opened successfully \n");


    id = new char(IW_ESSID_MAX_SIZE+1);
    wreq.u.essid.pointer = id;
    if (ioctl(sockfd,SIOCGIWESSID, &wreq) == -1) {
        fprintf(stderr, "Get ESSID ioctl failed \n");
        fprintf(stderr, "errno = %d \n", errno);
        fprintf(stderr, "Error description : %s\n",strerror(errno));
        exit(2);
    }
    printf("IOCTL Successfull\n");
    printf("ESSID is %s\n", wreq.u.essid.pointer);
    exit(0);
}

我收到以下错误:

  > 1. Get ESSID ioctl failed 
  > 2. errno = 7 
  > 3. Error description : Argument list too long

Answer 1

在使用werq之前，你应该先设置好长度，检查这个，

int sockfd;
    char * id;
   id = new char[IW_ESSID_MAX_SIZE+1];

    struct iwreq wreq;
    memset(&wreq, 0, sizeof(struct iwreq));
    wreq.u.essid.length = IW_ESSID_MAX_SIZE+1;

    sprintf(wreq.ifr_name, IW_INTERFACE);

    if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        fprintf(stderr, "Cannot open socket \n");
        fprintf(stderr, "errno = %d \n", errno);
        fprintf(stderr, "Error description is : %s\n",strerror(errno));
        exit(1);
    }
    printf("\nSocket opened successfully \n");

    wreq.u.essid.pointer = id;
    if (ioctl(sockfd,SIOCGIWESSID, &wreq) == -1) {
        fprintf(stderr, "Get ESSID ioctl failed \n");
        fprintf(stderr, "errno = %d \n", errno);
        fprintf(stderr, "Error description : %s\n",strerror(errno));
        exit(2);
    }

    printf("IOCTL Successfull\n");

    printf("ESSID is %s\n", (char *)wreq.u.essid.pointer);