alphabet.bash: update with more bash commands
alphabet.bash: update with more bash commands

erictleung/programming-notes,erictleung/programming-notes,erictleung/programming-notes,erictleung/programming-notes,erictleung/programming-notes,erictleung/programming-notes,erictleung/programming-notes,erictleung/programming-notes,erictleung/programming-notes