# demonstrate use of PATH variable
  528  which ls
  529  ls
  530  cd cse374_demos/03/
  631  wget http://courses.cs.washington.edu/courses/cse374/15wi/lectures/lec3scripts.tar
  632  tar xf lec3scripts.tar
  532  cat make_thumbnail1
  533  make_thumbnail1 mtn.jpg thumb.jpg
  534  ls
  535  echo $PATH
  536  clear
  537  PATH=$PATH:`pwd`
  538  echo $PATH
  539  make_thumbnail1 mtn.jpg thumb.jpg
  540  ls thumb.jpg 
  541  ls
# demonstrate variable assignment and export
  542  course=cse374
  543  echo $course
  544  bash
# in the child shell
     echo $course
     exit

  545  export course
  546  bash
# in the child shell
     echo $course
     exit

  547  clear
  548  printenv 
  549  printenv | grep course
  550  man env
  551  man printenv
  552  env
  553  clear
  554  i=10
  555  j=20
  556  k=$i + $j
  557  k=$i+$j
  558  echo $k
  559  ((k=$i+$j))
  560  echo $k
  561  ((k=i+j))
  562  echo $k
  563  ((k=i+j+h))
  564  echo $k
  565  vim makeNFiles
  566  chmod +x makeNFiles 
  567  ./makeNFiles 
  568  ./makeNFiles 2 cse
  569  vim makeNFiles
  570  ./makeNFiles 2 cse
  571  vim makeNFiles
  572  ./makeNFiles 2 cse
  573  vim makeNFiles
  574  ./makeNFiles 2 cse
  575  ./makeNFiles 2 cse
  576  ls -l cse*
  577  clear
  578  for value in 2 4 6 8; do echo Count $value; done
  579  for value in `seq 1 10`; do echo Count $value; done
  580  ls
  581  ls for filename in *; do echo $filename; done
  582  clearn
  583  clear

# strings and quoting
  584  echo m*
  585  ls *
  586  x=*
  587  ls $x
  588  echo x
  589  echo $x
  591  clear
  592  echo *
  593  echo "$x"
  594  x=*
  595  ls $x
  596  echo '$x hello'
  597  echo "$x hello"
  598  echo $x hello

# careful: if you have a typo, variable value defaults to empty
  599  ops=7
  600  ls $oops
  601  ls

# don't use set
  602  man set
  603  set foo=blah
  604  echo $foo

  607  ls
  610  ((k=i+j))
  611  echo $k
  612  ls
  613  exit
  614  history
  615  history > lec4.history