What is right way to show folder usage in megabytes [closed]
You are comparing apples and oranges.
Please note that ls -s will give the size of a file based on the length of the actual data in the file.
By default the du command will give a size based disk usage. Since disk space gets allocated in blocks, and the lengths of files are hardly ever integer multiples of the block size, you end up with a block that's only partially filled with data but which can't be used by another file.
In other words, if your file-system has a blocksize of 512 bytes, a file of 1 byte length will take up 512 bytes on disk, the same as a file of 511 bytes. A file of 513 bytes will take up 2 blocks and 1024 bytes of disk space.
The total sum du file disk usages will almost always be more than the sum of ls -s file file sizes, especially when you have many (small) files and/or very large block sizes.
Using the du -b switch will NOT count blocks, but behave like ls -s:
-bequivalent to--apparent-size --block-size=1--apparent-size
print apparent sizes, rather than disk usage; although the apparent size is usually smaller, it may be larger due to holes in ('sparse') files, internal frag‐ mentation, indirect blocks, and the like-h, --human-readable
print sizes in human readable format (e.g., 1K 234M 2G)
du -sh will convert the total number of blocks to a human readable format,du -bh will print the sum of apparent sizes, in human readable format.
In my Maildir, with many small files that differs quite a bit:
$ du -bs cur/
84088436 cur/
$ du -s cur/
91800 cur/
$ du -sh cur/
90M cur/
$ du -bh cur/
81M cur/
EDIT With regards to converting to human readable output and megabytes, please don't overlook the whole "controversy' of human readable in SI decimal prefixes versus binary multiples, powers of 1000 versus powers of 1024.
See for background this page: https://www.gnu.org/software/coreutils/manual/html_node/Block-size.html on how GNU utilities such as ls and du display them.
The capital M in du -h output stands for 1,048,576 bytes.