Why is my code not doing what I want it to do? I have 3 files that I want to process
that are in format file123, file456, file789.

echo "Processing each file one at a time..."

cd $dir
ls -r1 file???.dat > input.dat

exec < input.dat
    IFS='|'
    while read INPUT_FILE ; do
          echo INPUT_FILE = $INPUT_FILE 1>/dev/null
          echo "Processing file $INPUT_FILE..."

          if [[ -s  $INPUT_FILE ]]; then
              ksh script1.ksh
          else
             echo "$INPUT_FILE was empty."
             exit 1
          fi

          echo "Renaming processed file $INPUT_FILE..."
          mv $INPUT_FILE $INPUT_FILE.done
    done