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IOKit provides access to devices. It is an object-oriented framework leveraged by programmers for creating device drivers. It uses a subset of Embedded-C++ as its lingua franca, but the user space client API is wrapped into C APIs.


Two C snippets showing how to retrieve the MAC address via IOKit.

/*

taken from: http://developer.apple.com/mac/library/samplecode/GetPrimaryMACAddress/Introduction/Intro.html

compile with:

gcc -Wall -O3 -x objective-c -fobjc-exceptions -framework Foundation -framework CoreFoundation \
    -framework IOKit -o GetPrimaryMACAddress GetPrimaryMACAddress.c

./GetPrimaryMACAddress

File:           GetPrimaryMACAddress.c

Description:    This sample application demonstrates how to do retrieve the Ethernet MAC
                address of the built-in Ethernet interface from the I/O Registry on Mac OS X.
                Techniques shown include finding the primary (built-in) Ethernet interface,
                finding the parent Ethernet controller, and retrieving properties from the
                controller's I/O Registry entry.
            
Copyright:      Copyright 2001-2005 Apple Computer, Inc. All rights reserved.

Disclaimer:     IMPORTANT:  This Apple software is supplied to you by Apple Computer, Inc.
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Change History (most recent first):
    
        <3>     09/15/05    Updated to produce a universal binary. Use kIOMasterPortDefault
                            instead of older IOMasterPort function. Print the MAC address
                            to stdout in response to <rdar://problem/4021220>.
        <2>     04/30/02    Fix bug in creating the matching dictionary that caused the
                            kIOPrimaryInterface property to be ignored. Clean up comments and add
                            additional comments about how IOServiceGetMatchingServices operates.
        <1>     06/07/01    New sample.

*/

#include

#include <CoreFoundation/CoreFoundation.h>

#include <IOKit/IOKitLib.h> #include <IOKit/network/IOEthernetInterface.h> #include <IOKit/network/IONetworkInterface.h> #include <IOKit/network/IOEthernetController.h>

static kern_return_t FindEthernetInterfaces(io_iterator_t *matchingServices); static kern_return_t GetMACAddress(io_iterator_t intfIterator, UInt8 *MACAddress, UInt8 bufferSize);

// Returns an iterator containing the primary (built-in) Ethernet interface. The caller is responsible for // releasing the iterator after the caller is done with it. static kern_return_t FindEthernetInterfaces(io_iterator_t *matchingServices) { kern_return_t kernResult; CFMutableDictionaryRef matchingDict; CFMutableDictionaryRef propertyMatchDict;

// Ethernet interfaces are instances of class kIOEthernetInterfaceClass. 
// IOServiceMatching is a convenience function to create a dictionary with the key kIOProviderClassKey and 
// the specified value.
matchingDict = IOServiceMatching(kIOEthernetInterfaceClass);

// Note that another option here would be:
// matchingDict = IOBSDMatching("en0");
    
if (NULL == matchingDict) {
    printf("IOServiceMatching returned a NULL dictionary.\n");
}
else {
    // Each IONetworkInterface object has a Boolean property with the key kIOPrimaryInterface. Only the
    // primary (built-in) interface has this property set to TRUE.
    
    // IOServiceGetMatchingServices uses the default matching criteria defined by IOService. This considers
    // only the following properties plus any family-specific matching in this order of precedence 
    // (see IOService::passiveMatch):
    //
    // kIOProviderClassKey (IOServiceMatching)
    // kIONameMatchKey (IOServiceNameMatching)
    // kIOPropertyMatchKey
    // kIOPathMatchKey
    // kIOMatchedServiceCountKey
    // family-specific matching
    // kIOBSDNameKey (IOBSDNameMatching)
    // kIOLocationMatchKey
    
    // The IONetworkingFamily does not define any family-specific matching. This means that in            
    // order to have IOServiceGetMatchingServices consider the kIOPrimaryInterface property, we must
    // add that property to a separate dictionary and then add that to our matching dictionary
    // specifying kIOPropertyMatchKey.
        
    propertyMatchDict = CFDictionaryCreateMutable(kCFAllocatorDefault, 0,
                                                  &kCFTypeDictionaryKeyCallBacks,
                                                  &kCFTypeDictionaryValueCallBacks);

    if (NULL == propertyMatchDict) {
        printf("CFDictionaryCreateMutable returned a NULL dictionary.\n");
    }
    else {
        // Set the value in the dictionary of the property with the given key, or add the key 
        // to the dictionary if it doesn't exist. This call retains the value object passed in.
        CFDictionarySetValue(propertyMatchDict, CFSTR(kIOPrimaryInterface), kCFBooleanTrue); 
        
        // Now add the dictionary containing the matching value for kIOPrimaryInterface to our main
        // matching dictionary. This call will retain propertyMatchDict, so we can release our reference 
        // on propertyMatchDict after adding it to matchingDict.
        CFDictionarySetValue(matchingDict, CFSTR(kIOPropertyMatchKey), propertyMatchDict);
        CFRelease(propertyMatchDict);
    }
}

// IOServiceGetMatchingServices retains the returned iterator, so release the iterator when we're done with it.
// IOServiceGetMatchingServices also consumes a reference on the matching dictionary so we don't need to release
// the dictionary explicitly.
kernResult = IOServiceGetMatchingServices(kIOMasterPortDefault, matchingDict, matchingServices);    
if (KERN_SUCCESS != kernResult) {
    printf("IOServiceGetMatchingServices returned 0x%08x\n", kernResult);
}
    
return kernResult; }

// Given an iterator across a set of Ethernet interfaces, return the MAC address of the last one. // If no interfaces are found the MAC address is set to an empty string. // In this sample the iterator should contain just the primary interface. static kern_return_t GetMACAddress(io_iterator_t intfIterator, UInt8 *MACAddress, UInt8 bufferSize) { io_object_t intfService; io_object_t controllerService; kern_return_t kernResult = KERN_FAILURE;

// Make sure the caller provided enough buffer space. Protect against buffer overflow problems.
if (bufferSize < kIOEthernetAddressSize) {
    return kernResult;
}

// Initialize the returned address
bzero(MACAddress, bufferSize);

// IOIteratorNext retains the returned object, so release it when we're done with it.
while ( (intfService = IOIteratorNext(intfIterator)) )
{
    CFTypeRef   MACAddressAsCFData;        

    // IONetworkControllers can't be found directly by the IOServiceGetMatchingServices call, 
    // since they are hardware nubs and do not participate in driver matching. In other words,
    // registerService() is never called on them. So we've found the IONetworkInterface and will 
    // get its parent controller by asking for it specifically.
    
    // IORegistryEntryGetParentEntry retains the returned object, so release it when we're done with it.
    kernResult = IORegistryEntryGetParentEntry(intfService,
                                               kIOServicePlane,
                                               &controllerService);
    
    if (KERN_SUCCESS != kernResult) {
        printf("IORegistryEntryGetParentEntry returned 0x%08x\n", kernResult);
    }
    else {
        // Retrieve the MAC address property from the I/O Registry in the form of a CFData
        MACAddressAsCFData = IORegistryEntryCreateCFProperty(controllerService,
                                                             CFSTR(kIOMACAddress),
                                                             kCFAllocatorDefault,
                                                             0);
        if (MACAddressAsCFData) {
            CFShow(MACAddressAsCFData); // for display purposes only; output goes to stderr
            
            // Get the raw bytes of the MAC address from the CFData
            CFDataGetBytes(MACAddressAsCFData, CFRangeMake(0, kIOEthernetAddressSize), MACAddress);
            CFRelease(MACAddressAsCFData);
        }
            
        // Done with the parent Ethernet controller object so we release it.
        (void) IOObjectRelease(controllerService);
    }
    
    // Done with the Ethernet interface object so we release it.
    (void) IOObjectRelease(intfService);
}
    
return kernResult; }

int main(int argc, char argv[]) { kern_return_t kernResult = KERN_SUCCESS; // on PowerPC this is an int (4 bytes) /


/*

getmacaddress - get MAC address

C snippet posted by Guiyon on Apr 23, 2009, 10:03 AM at:

“how to find mac address using xcode”, http://forums.macrumors.com/showthread.php?t=689645

compile with:

gcc -Wall -O3 -x objective-c -fobjc-exceptions -framework Foundation -framework CoreFoundation -framework IOKit -o getmacaddress getmacaddress.c

./getmacaddress

“One important thing to note is that the CF* and NS* classes are toll-free bridged. That is, if you have some CFStringRef, for example, you can just typecast it to NSString* and use it as you would an NSString. This also means the same retain/release requirements apply.”

*/

#import <Foundation/Foundation.h>

#include <IOKit/IOKitLib.h> #include <IOKit/network/IOEthernetInterface.h> #include <IOKit/network/IOEthernetController.h>

static NSDictionary* GetMACAddresses( io_iterator_t netIterator ); static kern_return_t FindNetworkInterfaces( io_iterator_t services ); static NSString bytesToHexString( NSData* data );

int main (int argc, const char * argv[]) { io_iterator_t intfIterator; kern_return_t kernResult = KERN_FAILURE;

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

// NSLog(@”Detecting Network Interfaces…”);

kernResult = FindNetworkInterfaces( &intfIterator ); if( KERN_SUCCESS != kernResult ) { printf( “findNetworkInterfaces failed\n” );

} else {

// NSLog( @"Found one of more valid interfaces. Extracting MAC addresses..." );

NSDictionary* intfDictionary = GetMACAddresses( intfIterator );

/*
for( id key in intfDictionary ) {
  NSLog( @"  %@  =>  %@", key, [intfDictionary objectForKey: key] );
}    */

/* ADDED !!! / / more portable code than: for( id key in intfDictionary ) { … / NSArray keys = intfDictionary allKeys] sortedArrayUsingSelector:@selector(caseInsensitiveCompare:)]; int num = [keys count]; int i; for (i = 0; i < num; i++) { /* [[NSLog( @” %@ => %@”, [keys objectAtIndex: i], [intfDictionary objectForKey: [keys objectAtIndex: i]] ); */ printf(“%s => %s\n”, keys objectAtIndex: i] UTF8String], [[intfDictionary objectForKey: [keys objectAtIndex: i UTF8String]); }

IOObjectRelease( intfIterator );   }

/* [pool drain]; */ [pool release];

return 0; } /* Search through each of the Network interfaces identified

while( ( interfaceService = IOIteratorNext(netIterator) ) ) { CFTypeRef MACAddrAsCFData = NULL; CFTypeRef BSDNameAsCFString = NULL;

kernResult = IORegistryEntryGetParentEntry( interfaceService,
                                            kIOServicePlane,
                                            &controllerService );
if( KERN_SUCCESS != kernResult ) {
  printf( "IORegistryEntryGetParentEntry failed with 0x%08x\n", kernResult );
} else {
  MACAddrAsCFData = IORegistryEntryCreateCFProperty( controllerService,
                                                     CFSTR(kIOMACAddress),
                                                     kCFAllocatorDefault,
                                                     0 );
  
  BSDNameAsCFString = IORegistryEntryCreateCFProperty( interfaceService,
                                                       CFSTR("BSD Name"),
                                                       kCFAllocatorDefault,
                                                       0 );
  
  if( MACAddrAsCFData && BSDNameAsCFString ) {
    if( nil == etherDictionary ) {
      etherDictionary = [[NSMutableDictionary alloc] init]; 
    }
    
    [etherDictionary setObject:bytesToHexString((NSData*)MACAddrAsCFData)
                        forKey:(NSString*)BSDNameAsCFString];
    
  }

  if( nil != BSDNameAsCFString ) {
        CFRelease( BSDNameAsCFString );
  }

  if( nil != MACAddrAsCFData ) {
        CFRelease( MACAddrAsCFData );
  }
}   }

return (nil == etherDictionary) ? nil : (NSDictionary)[etherDictionary autorelease]; } / Search through the IOServicePlane and find any services that

kernResult = IOMasterPort( MACH_PORT_NULL, &machPort ); if( KERN_SUCCESS != kernResult ) { printf( “IOMasterPort failed: %d\n”, kernResult ); }

matchClasses = IOServiceMatching( kIOEthernetInterfaceClass ); if( NULL == matchClasses ) { printf( “IOServiceMatching returned a NULL dictionary” ); }

kernResult = IOServiceGetMatchingServices( machPort, matchClasses, services ); if( KERN_SUCCESS != kernResult ) { printf( “IOServiceGetMatchingServices failed: %d\n”, kernResult ); }

return kernResult; } static NSString* bytesToHexString( NSData* data ) { NSMutableString* result = [[NSMutableString alloc] initWithCapacity: [data length] « 1]; UInt8* mbytes = (UInt8*)[data bytes]; char hBytes[8] = {‘\0’}; int i = 0;

for( ; i < [data length]; i++ ) { snprintf( hBytes, 3, “%02X”, mbytes[ i ] ); if( 0 == i ) { [result appendFormat:@”%s”, hBytes]; } else { [result appendFormat:@”:%s”, hBytes]; } }

return (NSString*)[result autorelease]; }


A command line tool to list mounted USB devices and their respective volume paths; uses IOKit and man 2 getfsstat to get the job done.

The man 2 getfsstat code could be replaced by Apple’s IOKit-based sample code VolumeToBSDNode though.

/*

usbdevs - list mounted USB devices & their volume paths on Mac OS X

References:

compile with:

gcc -Wall -O3 -x objective-c -fobjc-exceptions -framework Foundation -framework CoreFoundation \ -framework IOKit -o usbdevs usbdevs.c

usage:

./usbdevs ./usbdevs -z | xargs -0 printf “%s\n”

*/

#import #import #import #import <sys/param.h> #import <sys/ucred.h> #import <sys/mount.h>

#import <Foundation/Foundation.h> #import <CoreFoundation/CoreFoundation.h> #import <IOKit/IOKitLib.h> #import <IOKit/IOMessage.h> #import <IOKit/IOCFPlugIn.h> #import <IOKit/usb/IOUSBLib.h> #import <IOKit/IOBSD.h>

int main(int argc, char *argv[]) {

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

mach_port_t master_port; kern_return_t k_result = KERN_FAILURE; io_iterator_t iterator = 0; io_service_t usb_device_ref; CFMutableDictionaryRef matching_dictionary = NULL;

char devicePath[MAXPATHLEN*2] = {0};

int print0 = 0; size_t pathlen = 0; const char *deviceName = 0; CFStringRef bsdName = NULL;

if (argc > 2) return 1;

if (argc == 2) { if ( (strcmp(argv[1], “-z”) == 0) ) { print0 = 1; } else if ( (strcmp(argv[1], “-h”) == 0) ) { fprintf(stdout, “usage: %s [-hz]\n\t-z: null-terminate output (ASCII nul character)\n”, argv[0]); return 0; }else{ fprintf(stderr, “usage: %s [-hz]\n”, argv[0]); return 1; } }

// man 2 getfsstat // getfsstat – get list of all mounted file systems

struct statfs *buf; int flags = MNT_NOWAIT, num_fs, num_stat, i; unsigned bufsz;

num_fs = getfsstat(NULL, 0, flags); if (num_fs < 0) { perror(“unable to count mounted filesystems: getfsstat”); exit(1); }

bufsz = sizeof(*buf) * num_fs; buf = malloc(bufsz); if (!buf) { perror(“unable to allocate %u statfs structs”); exit(1); }

//fprintf(stderr, “p=%p\n”, buf);

num_stat = getfsstat(buf, bufsz, flags); if (num_stat < 0) { perror(“unable to getfsstat”); exit(1); }

if (num_stat != num_fs) { fprintf(stderr, “Hmm, expected %u, got %d.\n”, num_fs, num_stat); }

// first create a master_port k_result = IOMasterPort(MACH_PORT_NULL, &master_port); if (KERN_SUCCESS != k_result) { fprintf(stderr, “could not create master port, err = %d\n”, k_result); }

if ((matching_dictionary = IOServiceMatching(kIOUSBDeviceClassName)) == NULL) { fprintf(stderr, “could not create matching dictionary, err = %d\n”, k_result); }

k_result = IOServiceGetMatchingServices(master_port, matching_dictionary, &iterator); if (KERN_SUCCESS != k_result) { fprintf(stderr, “could not find any matching services, err = %d\n”, k_result); }

while ((usb_device_ref = IOIteratorNext(iterator))) {

  bsdName = (CFStringRef) IORegistryEntrySearchCFProperty (usb_device_ref,
                                                           kIOServicePlane,
                                                           CFSTR ( kIOBSDNameKey ),
                                                           kCFAllocatorDefault,
                                                           kIORegistryIterateRecursively );
  if (!bsdName) continue;

  deviceName = [[NSString stringWithFormat: @"%@", bsdName] UTF8String];

  //printf("%s\n", deviceName);

  devicePath[0] = '\0';
  strcat(devicePath, "/dev/");
  strcat(devicePath, deviceName);

  pathlen = strlen(devicePath);

  //printf("pathlen: %zu\n", pathlen);
  //printf("devicePath: %s\n", devicePath);

  for (i = 0; i < num_stat; i++) {

     if (strncmp(buf[i].f_mntfromname, devicePath, pathlen) == 0)
     {
        if ( print0 == 0 )
           fprintf(stdout, "%s %s\n", buf[i].f_mntfromname, buf[i].f_mntonname);
        else
           fprintf(stdout, "%s %s%c", buf[i].f_mntfromname, buf[i].f_mntonname, 0);  
           // null-terminate output (ASCII nul character)
     }

  }

  CFRelease(bsdName);

  IOObjectRelease(usb_device_ref);            // no longer need this reference

} // while

[pool release];

return 0;

}