ls 
 ls a "b c"
 ls
 ls woiwvmoiewvoiwv
 mail djg -s "welcome from class"
 cd lec3play
 ls
 mail djg -s "here is the file" < listhome
 cat listhome 
 history
 ls
 ls ioewfoi
 ls > foo
 ls oiewfioewf > foo
 ls oiewfioewf 2> foo
 history > bar
 less bar
 rm bar
 man less
  
 history | less
 ls
 history | grep pwd 
 history | grep pwd | grep 721
 history | grep pwd | grep 721 > bar
 cat bar
 ls
 display me.jpg &
 djpeg me.jpg | pnmscale -xysize 100 150 | cjpeg > me_small.doesnotmatter
 display me_small.doesnotmatter &
 
 ls
 ls | echo "hi"
 ls || echo "hi"
 ls wefoiuewf || echo "hi"
 ls wefoiwefmiewf
 echo $?
 ls me.jpg
 echo $?
 
 pwd     
 cd pwd
 cd `pwd`
 ls
 pwd
 echo `pwd`
 whoami
 mkdir `whoami`
 ls
 whoami | mkdir
 echo \!
 echo "!"
 echo ">"
 echo '!'
 echo '!weiwiviewj*($@'
 
 alias
 ls
 /bin/ls
 unalias ls
 ls
 
 alias lsh="ls ~"
 alias
 lsh
 lsh me.jpg
 lsh me.jpg -l
 ls    
 cat listhome 
 listhome
 
 ./listhome
 pwd
 ls -l
 chmod 600 listhome
 ./listhome
 chmod 700 listhome
 ./listhome
 
 ./make_thumbnail1 me.jpg me_small.jpg
 ls -l
 ./make_thumbnail1 me.jpg
 cat make_thumbnail2
 
 ./make_thumbnail2
 ./make_thumbnail2 me.jpg
 ./make_thumbnail2 me.jpg me_again.jpg
 ls -l
 ./make_thumbnail2 me.jpg me_again.jpg foo.jpg
 
 countdown x y z
 ./countdown x y z 
 ./countdown x "y z"