1  cat story.txt 
    2  sed -e 's/stormy night/dreary day/g' story.txt 
    3  cat story.txt 
    4  sed 's/\(..*\).*\1/&/' story.txt 
    5  sed 's/\(..*\).*\1/\1/' story.txt 
    6  sed 's/\([a-z]*\).*\1/\1/' story.txt 
    7  cat story.txt 
    8  sed '/^$/d' story.txt 
    9  cat candidates.txt 
   10  sed 's/\(.*\), \(.*\)/\2 \1/' candidates.txt 
   11  sed 's/\(.*\), \(.*\)/\2 \1/' candidates.txt | sort
   12  sort candidates.txt | sed 's/\(.*\), \(.*\)/\2 \1/'
   13  sort candidates.txt | sed -e 's/\(.*\), \(.*\)/\2 \1/' -e '/Fey/d'
   14  ls
   15  sed 's/Hamlet/Hamlet, the great Dane/' hamlet.txt | grep Hamlet
   16  sed 's/Hamlet/Hamlet, the great Dane,/' hamlet.txt | grep Hamlet
   17  history > lec7.history