Shell Programming and Scripting

There are several different implementations of "ls".
What Operating System and version are you running?

Whatever the version, "ls -ltr" will list items which are not files (e.g. Directories, Special Files, Pipes, Links etc. and also output a "Total" line". A general purpose tool will need to cater for non-files.
If you just want a rough total size of a directory and its subdirectories then see the "du" command (with paramters).

to Methyl's point: if you're trying to stabilize your output to ensure that you can always expect bytes, you'll want to apply a filter that only picks up files. You'll probably want to query the system, using something like the find utility and wrap your ls around it, like this:

Code:

ls -ltr $(find /opt/my/directory/to_search -type f -ctime 0 )

Again, ls can vary by your particular situation, but -l is fairly standard across all versions to provide the long file details. The -h option you'd mentioned at one point is intended as "human-readable", but this itself depends on how computer literate the human reading it is.