If we want to get the byte size of a block device or one of its partitions without calling any binary, and in a way that will always work, is it correct to do:
/sys/block/sda/sda1/size
or /sys/block/sda/size
Multiplied by :
/sys/block/sda/queue/physical_block_size
Or is it logical_block_size or hw_sector_size ?
Is there a better approach?
After more research I finally found the answer:
Linux always considers sectors to be 512 bytes long independently of the devices real block size.
According to the source: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/types.h?id=v4.4-rc6#n121
I was led there by this comment: Determine the size of a block device
So as silly as it may seem the [size] should simply be multiplied by 512.
I just hope it will still be a correct assumption 15 years from now, because I don't want my programs to be broken. physical_block_size seems wrong because it can sometimes be 4096 as I found with some Googling, but maybe it is still worth reading logical_block_size or hw_sector_size even if it will always be 512? Any comments on this?