第一种方法，采用读取文件的方式。在linux下，任何一种设备都可看成文件。通过分析相关文件信息，可得知WIFI设备是否存在；代码示例如下：

static void WIFI_Enum_Device(void)
{
char buff[1024];
FILE * fh;

/* Check if /proc/net/wireless is available */
fh = fopen(PROC_NET_WIRELESS, "r");

if(fh != NULL)
{
/* Success : use data from /proc/net/wireless */

/* Eat 2 lines of header */
fgets(buff, sizeof(buff), fh);
fgets(buff, sizeof(buff), fh);

/* Read each device line */
while(fgets(buff, sizeof(buff), fh))
{
char name[IFNAMSIZ + 1];
char *s;

/* Skip empty or almost empty lines. It seems that in some
* cases fgets return a line with only a newline. */
if((buff[0] == '\0') || (buff[1] == '\0'))
continue;

/* Extract interface name */
s = WIFI_Get_DeviceName(name, sizeof(name), buff);

if(!s)
{
/* Failed to parse, complain and continue */
#ifndef IW_RESTRIC_ENUM
fprintf(stderr, "Cannot parse " PROC_NET_DEV "\n");
#else
fprintf(stderr, "Cannot parse " PROC_NET_WIRELESS "\n");
#endif
}
else
/* Got it, save the name about this interface */

{//we always use the first detected device when doing first time detecting
if(s_DeviceCount == 0)
{
if(strcmp(s_Deviceinfo.DeviceName,name))
{
memset((char *)&s_Deviceinfo, 0, sizeof(DeviceInfo_t));

memcpy(s_Deviceinfo.DeviceName,name,IFNAMSIZ);
}
if(strlen(s_SavedDevice) == 0)//this is the first detected device when doing first time detecting, we save it
memcpy(s_SavedDevice,name,IFNAMSIZ);
}
else
{//there is more than one device, we should use the first detected
if(!strcmp(s_SavedDevice,name))
{
memset((char *)&s_Deviceinfo, 0, sizeof(DeviceInfo_t));

memcpy(s_Deviceinfo.DeviceName,name,IFNAMSIZ);
}
}
s_DeviceCount++;
}
}

fclose(fh);
}

}

static char* WIFI_Get_DeviceName(char * name, /* Where to store the name */
int nsize, /* Size of name buffer */
char * buf) /* Current position in buffer */
{
char * end;

/* Skip leading spaces */
while(isspace(*buf))
buf++;

#ifndef IW_RESTRIC_ENUM
/* Get name up to the last ':'. Aliases may contain ':' in them,
* but the last one should be the separator */
end = strrchr(buf, ':');
#else
/* Get name up to ": "
* Note : we compare to ": " to make sure to process aliased interfaces
* properly. Doesn't work on /proc/net/dev, because it doesn't guarantee
* a ' ' after the ':'*/
end = strstr(buf, ": ");
#endif

/* Not found To big */
if((end == NULL) || (((end - buf) + 1) > nsize))
return(NULL);

/* Copy */
memcpy(name, buf, (end - buf));
name[end - buf] = '\0';

/* Return value currently unused, just make sure it's non-NULL */
return(end);
}