List all drives/partitions, and get /dev/rdisc device with Cocoa

Question

Is there a way to list available drives, similar to Disk Utility, and get the associated /dev/rdisk* device for it?

Disk Utility has access to this data - when you select a drive and press the Info button, it lists..

Partition Map Scheme : GUID Partition Table
Disk Identifier : disk0
Media Name : Hitachi HTS541612J9SA00 Media

..or select a partition:

Disk Identifier : disk0s3
Mount Point : /Volumes/BOOTCAMP

Is there a Cocoa API to get at this? If so, what is the best way to display this via Interface Builder?

Answer 1

As groundhog points out, the IORegistry is indeed the go-to source for all things device-related. The IOKit docs are very detailed and helpful; you should start with IOKit Fundamentals, then hit Accessing Hardware from Applications, then finally check out Device File Access Guide for Storage Devices if you want to get at information the BSD way.

In this case, you can make the Disk Arbitration framework do some of the heavy lifting of querying the IO registry and registering for notifications. This saves a lot of code, but to do everything you want to do, you'll eventually need to use IOKit functions with the underlying IOMedia object (see DADiskCopyIOMedia()).

You could readily write a Cocoa wrapper around the IOMedia objects that represent the disks in the IO registry, then use object controllers to bind properties to your UI.

Here's an example of registering for disk appearance notifications through the Disk Arbitration framework to get you started:

// gcc -Wall -framework Foundation -framework DiskArbitration disk_arbiter.m -o disk_arbiter
/* @file disk_arbiter.m
 * @author Jeremy W. Sherman
 * @date 2009-10-03
 *
 * Demonstrates registering for disk appeared notifications from
 * the DiskArbitration framework.
 *
 * Note that disk appeared notifications are delivered for all
 * already-appeared disks at the time of registration, and then
 * trickle in as the events actually happen thereafter.
 */
#import <Foundation/Foundation.h>
#import <DiskArbitration/DiskArbitration.h>
#import <signal.h>

sig_atomic_t sShouldExit = 0;

static void RegisterInterruptHandler(void);
static void HandleInterrupt(int);

static void OnDiskAppeared(DADiskRef disk, void *__attribute__((__unused__)));

int
main(void) {
  CFStringRef const kDARunLoopMode = kCFRunLoopDefaultMode;

  RegisterInterruptHandler();

  // Set up session.
  DASessionRef session = DASessionCreate(kCFAllocatorDefault);
  DARegisterDiskAppearedCallback(session, NULL/*all disks*/, OnDiskAppeared, (void *)NULL);
  DASessionScheduleWithRunLoop(session, CFRunLoopGetCurrent(), kDARunLoopMode);

  // Run event loop.
  printf("Starting...\n(Press Ctrl-C to exit.)\n\n");
  const Boolean kAndReturnAfterHandlingSource = TRUE;
  const CFTimeInterval kForOneSecond = 1.0;
  while (!sShouldExit)
    (void)CFRunLoopRunInMode(kCFRunLoopDefaultMode,
                             kForOneSecond, kAndReturnAfterHandlingSource);

  // Tear down and exit.
  printf("\nExiting...\n");
  DASessionUnscheduleFromRunLoop(session, CFRunLoopGetCurrent(), kDARunLoopMode);
  CFRelease(session);
  exit(EXIT_SUCCESS);
  return EXIT_SUCCESS;
}

static void
RegisterInterruptHandler(void) {
  struct sigaction sigact;
  sigact.sa_handler = HandleInterrupt;
  (void)sigaction(SIGINT, &sigact, NULL/*discard previous handler*/);
}

static void
HandleInterrupt(int __attribute__((__unused__)) signo) {
  sShouldExit = 1;
  RegisterInterruptHandler();
}


static void
OnDiskAppeared(DADiskRef disk, void *__attribute__((__unused__)) ctx) {
  printf("Lo, a disk appears!\n");
  CFShow(disk);
}

And here's output from a sample run:

$ ./disk_arbiter 
Starting...
(Press Ctrl-C to exit.)

Lo, a disk appears!
<DADisk 0x104f80 [0xa01c01a0]>{id = /dev/disk3}
Lo, a disk appears!
<DADisk 0x105b40 [0xa01c01a0]>{id = /dev/disk2s1}
Lo, a disk appears!
<DADisk 0x105ae0 [0xa01c01a0]>{id = /dev/disk2s2}
Lo, a disk appears!
<DADisk 0x105b60 [0xa01c01a0]>{id = /dev/disk2}
Lo, a disk appears!
<DADisk 0x105950 [0xa01c01a0]>{id = /dev/disk1}
Lo, a disk appears!
<DADisk 0x105bc0 [0xa01c01a0]>{id = /dev/disk1s1}
Lo, a disk appears!
<DADisk 0x105540 [0xa01c01a0]>{id = /dev/disk0}
Lo, a disk appears!
<DADisk 0x105660 [0xa01c01a0]>{id = /dev/disk0s1}
Lo, a disk appears!
<DADisk 0x1054a0 [0xa01c01a0]>{id = /dev/disk0s2}
^C
Exiting...

Answer 2

What you most likely are interested in is the IORegistry, which is conceptually described in the IO Kit Fundamentals