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#1300 File size in MB is inconsistent when viewing identical copies of pdf in different directories
When viewing identical copies of pdf files, the byte count is reliably the same, but the size in MB varies drastically. I think if both files are located in the same directory, they display the same MB size, but if the files are in different directories, the sizes will vary. I haven't been able to figure out if it's differing directory length, differeing directory component count, some other deterministic factor, or if it's random.
What do you mean by the size in MB? Which display? Can you describe a reproducible set of actions to take that reveals the problem?
Also, are you sure they are identical files, or could it be that one has notes and the other doesn't?
identical in size and in byte-by-byte comparison. reproducible by just
cp in.pdf /some/other/dir/out.pdf.edit: the attached images show a size difference of 0.6 MB though the byte count is identical. i have seen cases where the difference is around 10 MB (on a 100MB file).
Last edit: ricker 2019-04-29
Are they on the same volume, or perhaps some on a different kind of disk?
We just show the sizes that we get from the system. Though the two numbers do not represent the identical size numbers, one is the physical file size and the other the logical file size..
The files are on the same disk/volume, just different subdirectories. The size is consistenly identical when opening both files in Preview.
And they both have the same notes?
And does Finder's info window report the same sizes?
I don't know what sizes Preview reports.
But I still don't see what is necessarily a bug. If the sizes are reported differently, they probably are different. A bit surprising that this is so large, but I don't know much about how efficient the file system is.
Perhaps there are some permission issues with the directory containing file reporting the lower size. If we cannot get the full size numbers, we rely on some more inaccurate methods to get an approximate size.
files are identical bytewise (e.g.
cp in.pdf out.pdf)yes, all apple tools show 4.6 MB for both files. ,
ls -lhand Firefox pdf viewer show 4.4MB. That might be a Mebibyte vs Megabyte thing though. (Edit: this is confirmed: 4.4 * 1.049 = 4.6) Nonetheless, every tool shows the file size the same for both files.Preview reports the same size as Finder (4.6 MB)
If the files are bytewise identical and every other tool shows the identical file size...
Last edit: ricker 2019-04-29
You should realize that there does not exast an "the file size". There are many ways to measure the file size, I can get at least 4. And we show two numbers representing two different ways to measure the file size. In particular, the MB size is not the bytewise size of the content, it is the physical size the file occupies on the disk, which can be larger (i.e. the space reserved for it). So they don't need to be the same. And, again, I do not know which of these sizes Preview or Finder report. So I do not necessarily see a bug. Again, is there a difference between the configration of the two files, like permissions of the file and/or the containing folders?
speaking of filesystem, after upgrading to Mojave, my fs is now APFS. and a little googling i found this: https://forums.developer.apple.com/thread/103162
which says using FSGetCatalogInfo, which is now deprecated, might not work properly with APFS
This is about inode, we don't use an inode. I don't directly see why the file sizes would be a problem, they certainly are not too big here. And the ones we use do not have modern replacement AFAICS.
Using a different API to calculate the file sizes.