Why do Finder and du report different file size?

Question

I am writing a geektool 3 script to show the size of a particular VMware Fusion virtual machine. Such .vmwarevm "file" is really a packaged directory.

Get Info in Finder says the file is "52.91 GB". I run the following du command to get the file size:

> du -hs ~/Documents/Virtual\ Machines.localized/MY-PRECIOUS-7.vmwarevm | awk '{print $1}'

This du -hs command returns the file size as "49G". What accounts for the difference from what Finder reports?

Alternatively, I have tried replacing the -s option with the -d option like so:

du -hd ~/Documents/Virtual\ Machines.localized/MY-PRECIOUS-7.vmwarevm | awk '{print $1}'

This du -hd command returns the file size as "59G". What accounts for the difference between Finder, du -hd, and du -hs?

Also, this du -hd command produces no output in geektool 3. What gives?

Answer 1

Not an Mac OS X user but I read somewhere that Finder uses base-10 nowadays.

Could the difference be that du still uses base-2?

49.0 GiB * (1024^3 bytes / GB) = 52,613,349,376 bytes = 52.6 GB

(the small difference is because du is rounding to the nearest GB)

Answer 2

Nifle is correct. du returns base-2, Finder returns base-10, and 49GiB ≈ 52.91GB

The -d argument requires you to specify a depth. From experimenting just now, it appears if you give something besides a number for depth, it eats the argument you specified and behaves as if you did -d 0. The 59G you're getting is the size of the current directory, not the size of the vmwarevm file.

Here is the experiment I ran:

[~]$ ls -d Code
Code/

[~]$ du -h -s Code
8.3M    Code

[~]$ du -h -d 0 Code
8.3M    Code

[~]$ du -h -d Code
 38G    .           <-- this is the size of ~/

[~]$ du -h -d 0
 38G    .

You might want to read the Mac OS X du(1) manpage for more information.

Answer 3

Also note that "du" returns the actual disk space used, whereas other tools will return the allocated space. Where you have sparse files these 2 values can be quite different - I have a file that has 2 TB allocated to it but it is only occupying about 200 MB of disk space.