503  PS1="${PS1}\n--> "
  504  cd ../..
  505  ls -R
  506  cd 279lectures/
  507  cd 279lect10-2
  508  ls
  510  ln -s loopy.txt linky.txt
  511  mkdir stuff
  512  ls -F
  513  ls test*.txt
  514  ls -l test*.txt
  515  vi test1.txt
  516  ls -l
  517  ls -l test*.txt
  518  vi test10.txt
  519  ls -l test*.txt
  520  ls -lu test*.txt
  521  vi test7.txt
  522  ls -lu test*.txt
  523  ls -t test*.txt
  524  ls -lt test*.txt
  525  ls -lut test*.txt
  526  ls -tF | grep "\*$"
  527  more numbers.txt 
  528  head numbers.txt
  529  head -n 3 numbers.txt
  530  ls -tF | grep "\*$" | head -n 5 
  531  tail numbers.txt
  532  tail -n -5 numbers.txt
  533  tail -n 5 numbers.txt
  534  tail -n +5 numbers.txt
  535  tail -c 5 numbers.txt
  536  emacs loopy-print.sh
  537  rm loopy.txt
  538  loopy-print.sh 1 2 3 4 5 6 7 8 9 0 moo oink 10 15 20 &
  539  tail -f loopy.txt
  540  cat | tail -f
  541  ls | tail -n 15
  542  ls | tail -c 15
  543  tail -15 numbers.txt
  544  tail -5 numbers.txt
  545  ls | tail 15
  546  ls tail +15
  547  tail +15 numbers.txt
  548  emacs unix-stuff.txt 
  549  sed -e 's/UNIX/Linux/g' unix-stuff.txt
  550  sed -e 's/UNIX/Linux/' unix-stuff.txt
  551  sed -e 's/UNIX/Linux/2' unix-stuff.txt