最新做一个WIFI应用项目。如何检测WIFI USB设备是否插上了呢？特此共享。

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);

}

RETURN_TYPE APP_WIFI_DetectDevice(void)

{

char command[50] = {'\0'};

s_DeviceCount = 0;  //reset count

WIFI_Enum_Device();

s_LastDeviceCount = s_DeviceCount;

if(s_DeviceCount > 0)

{

sprintf(command,"ifconfig %s up",s_Deviceinfo.DeviceName);

system(command);  //boot up the device firstly

return SYS_NOERROR;

}

else

return SYS_FAILED;

}

第二种方法，利用linux ioctl函数读取I/O接口的相关信息。

/*****************************************************************************

*  Name        : trid_char * APP_NetLink_GetIFFLAGS(char *NetDev )

*  Description : Get net interface IFFLAGS

*  Params      : NetDev

*  Returns     : the string of the NetDev

*  Author/date : Danny.Hu /2011.11.16

*****************************************************************************/

RETURN_TYPE APP_NetLink_GetIFFlags( trid_char *NetDev )

{

int fd = -1;

int InterfaceFlags;

struct ifreq ifr;

memset(&ifr, 0, sizeof(ifr));

strcpy(ifr.ifr_name, NetDev);

fd = socket(AF_INET, SOCK_DGRAM, 0);

if (fd < 0)

{

printf("Cannot get control socket\n");

close(fd);

return SYS_FAILED;

}

else if( 0!=(ioctl(fd, SIOCGIFFLAGS, (char*)&ifr)) )

{

printf("Cannot get Network Interface Flags!\n");

close(fd);

return SYS_FAILED;

}

InterfaceFlags = ifr.ifr_flags;

printf("

if ( InterfaceFlags & IFF_UP)                        printf("Network %s is UP, ", NetDev);

if ( InterfaceFlags & IFF_BROADCAST)     printf("Network %s is BCAST, ", NetDev);

if ( InterfaceFlags & IFF_MULTICAST)      printf("Network %s is MCAST, ", NetDev);

if ( InterfaceFlags & IFF_LOOPBACK)       printf("Network %s is LOOP, ", NetDev);

if ( InterfaceFlags & IFF_POINTOPOINT)   printf("Network %s is P2P, ", NetDev);

printf(">\n");

close(fd);

return  SYS_NOERROR;

}