This is not a sort command, it is a pipeline containing three commands: ls, sort, and head
The sort command in the middle of this makes no sense: The options are interpreted as follows: -r reverses the sort order, -t the next argument (in this case -k) should be a single character which is used as the field delimiter separating fields in the input that is to be sorted. I don't believe that you have shown us what this argument is. The -k option with the option argument 4,4n says to sort the input data based on the 4th field and sort the values numerically (rather than alphabetically).

The first command in the pipeline (ls ${DEST_LOCATION}/${FILES}) will provide a list of files (one per line) that match the pattern to which ${DEST_LOCATION}/${FILES} expands. Without knowing how DEST_LOCATION and FILES were set, I have no idea what filenames are going to be sorted by the sort command. When the sort is completed, the last command in the pipeline (head -1) will print the 1st line and ignore everything else.

Please recheck this command line. For this pipeline to make any sense there has to be another argument to the ls command or the argument (-rt) to sort would have to be just -r instead, and there would need to be options given to ls to produce multi-column output with the 4th field being a numeric value. If the command was:

Code:

ls -l ${DEST_LOCATION}/${FILES} | sort -r -k 5,5n | head -1

the output would be a long format listing of the largest file matched by the pattern specified by ${DEST_LOCATION}/${FILES}.