#include <sys/param.h>
#include <sys/mount.h>

+(float)getTotalDiskSpaceInBytes {
	NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
	struct statfs tStats;
	statfs([[paths lastObject] cString], &tStats);
	float totalSpace = (float)(tStats.f_blocks * tStats.f_bsize);

    return totalSpace;
}

This approach relies on the handy Unix statfs() function that provides the required file system information. I coded it up and it worked on my 3.x devices. Fine I thought, I’m off and running. Then when testing on a 2.x device, it crashed. The problem looks to be differences in the compiler settings between the two OS versions. Rather than figure that out (I leave that as an exercise to the reader ), I continued my search and came across what I consider the “correct” solution since it uses the iPhone SDK itself, as given below.

+(float)getTotalDiskSpaceInBytes {
	float totalSpace = 0.0f;
	NSError *error = nil;
	NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
	NSDictionary *dictionary = [[NSFileManager defaultManager] attributesOfFileSystemForPath:[paths lastObject] error: &error];

	if (dictionary) {
		NSNumber *fileSystemSizeInBytes = [dictionary objectForKey: NSFileSystemSize];
		totalSpace = [fileSystemSizeInBytes floatValue];
	} else {
		DLog(@"Error Obtaining File System Info: Domain = %@, Code = %@", [error domain], [error code]);
	}

    return totalSpace;
}

As stated in the documentation, these interfaces wrapper the statfs() function, so they ultimately do the same thing, but they have been a part of the SDK since version 2.0! Testing verified my assumption and this approach works for me on my 2.x and 3.x devices and the numbers match what iTunes shows as well.

Post from iPhone Development Blog Copyright © 2011 Nick Dalton - iPhone Developer

How To Obtain Total and Available Disk Space on Your iPhone or iPod Touch