CSC152 2005S, Class 3: An Introduction to Unix

Admin
* Homework due
* Some notes on the homework (more Friday)
  * Grading policies
  * Structure of outlines
* Reading for Friday: An introduction to Java
  * Reading available later today

Overview:
* Questions on the reading?
* Lab

Reflections:
* Capitalization is important: Use CS152 not cs152
* Order is important in the chmod command (and in most commands)
* If you want to repeat (or modify) previous commands, you can use the up-arrow key to visit your previous commands
* To delete a file
  rm FILENAME
* To delete an empty directory
  rmdir DIRECTORYNAME
* chmod options
  chmod [ugoa][+-=][rwx] file
   u = user
   g = group
   o = other
   a = all
   + = add
   - = remove
   = = set
   r = read
   w = write
   x = execute
* You can only alias commands, you cannot alias names
* You cannot assign specific permissions for specific users
* USER IDs:
  bernstei, bishopbr, buckelij, dangelod, doleshai, greenbe1, hoyerrol, kellylor, khannab1, sainjusa, tsujonat, ugwimoni, wangjing
* Mac users can get to the MathLAN machines with
	ssh userid@lie.cs.grinnell.edu
  from the terminal window
  (use some machine name of your choice)

Questions:
* If you have execute permission on a directory, but no read permission, what can you do?
  You can access the files IF YOU ALREADY KNOW THEIR NAMES AND THEY PROVIDE PERMISSION FOR YOU TO ACCESS THEM
* What does read permission on a directory give you?
  You can list the files in the directory.  You can read the files themselves only if they give you read permission

* Why use a terminal rather than a graphical user interface?  
  * More fun
  * Don't have to move your hand from the keyboard to the mouse
  * Perhaps gives you a better understanding of the stuff
  * May allow you to access things you would not otherwise understand
  * Some activities can be accomplished more quickly.
  * Doesn't burden the computer as much