Linux C程序如何檢測WIFI無線USB網卡是否可用？
最新做一個WIFI應用項目。如何檢測WIFI USB設備是否插上了呢？特此共享。
第一種方法，采用讀取文件的方式。在linux下，任何一種設備都可看成文件。通過分析相關文件信息，可得知WIFI設備是否存在；代碼示例如下：
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;
}
第二種方法，利用linux ioctl函數讀取I/O接口的相關信息。
/*****************************************************************************
* 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;
}