what is the most reliable command to find actual size of a file linux

Question

Recently I tried to find out the size of a file using various command and it showed huge differences.

ls -ltr showed its size around 34GB (bytes rounded off by me ) while du -sh filename showed it to be around 11GB. while stat command showed the same to be around 34GB . Any idea which is the most reliable command to find actual size of the file ?

There was some copy operation performed on it and we are unsure of if this was appropriately done as after a certain time source file from where copy was being performed was removed by a job of ours.

Answer 1

There is no inaccuracy or reliability issue here, you're just comparing two different numbers: logical size vs physical size.

Here's Wikipedia's illustration for sparse files:

ls shows the gray+green areas, the logical length of the file. du (without --apparent-size) shows only the green areas, since those are the ones that take up space.

You can create a sparse file with dd count=0 bs=1M seek=100 of=myfile.

ls shows 100MiB because that's how long the file is:

$ ls -lh myfile
-rw-r----- 1 me me 100M Jul 15 10:57 myfile

du shows 0, because that's how much data it's allocated:

$ du myfile
0 myfile