outline

Why UNIX?

• Defacto web server standard
• Reliable
• Inexpensive

Why FTP and Telnet?

• Most of us not directly on server
• Allows us to connect to server from client
• We can work on client -> send to server
• Can work directly on server

Operating Systems in General

• "Traffic Cop"
• Control interactions between files, hardware, software, memory
• Provides user interface
• All have similar capabilities but very different implementations

Hierarchies

• 
• Search Yahoo for…   Options

Hierarchy Searching Algorithm

• Find the root
• 
• Look at the branches
  Three outcomes:
  -target is there - activate it
  -not there, but promising subcategory - go there
  and repeat steps
  -not there, nothing close - back up
  a level and repeat steps

Recursive Algorithm

• Begins with a large set
• Algorithm repeats on increasingly smaller subsets
• Eventually a trivial set remains

Other Trees

• Menus inside applications
• Start menu (Apple menu)
• Directory structures

Text Based Operating Systems

• DOS and UNIX
• Basically, the same things are available
• Instead of graphics (icons), commands are used
• Some memorization (or cheat card) is necessary

Exploring ds9 with FTP

• Graphic FTP programs
• Two file management programs

Exploring ds9 with Telnet

• Use of commands to implement same concept
• Java Telnet Client

The Critical UNIX Commands

• ls
• ls -l
• cd
• pwd
• cp
• mv
• chmod

cd - Change Directory

• UNIX stores files in a directory tree
• The cd command changes to the directory specified
• If you have a directory called mystuff off of the current directory, you could type cd mystuff to change to that directory
• To change back to a parent directory, type cd ..
• To change to your home directory, simply type cd
• Notes:
  directories are separated by forward slashes (/), NOT backslashes like DOS
  UNIX is case sensitive
  to locate which directory you are in, use the pwd command
  pwd stands for present working directory

ls - List

• List current directory
• Lists the files and subdirectories of the current directory
• ls -l = long listing, shows details of files (including permissions)
• There are many more - available by looking in man
• Notes:
  - ls by itself works like a DOS dir/w; it shows the files in columns
  -use ls -l to see the permissions of files and other details
  -if your list of files is too long for the screen, you can use ls | more

mkdir - Make Directory

• Creates a new subdirectory that is a child of the one you are on
• DOS equivalent = md
• Notes:
  -you must give the command a name for the directory
  -the name must be one word, and is case sensitive
  - mkdir mystuff will make a new directory called mystuff from my root directory

cp - Copy

• Copies a file to another file or another directory
• Notes:
  -works just like DOS copy command
  -cp myfile newfile will make a copy of myfile and call it newfile
  -if I have a directory called mystuff, cp myfile mystuff will make a copy of myfile and put it in mystuff
  -the ORIGINAL file stays there. cp just made a new version of it.

mv - Move

• Moves a file to a new place or renames it
• DOS equivalent:
  -RN works like the renaming behavior
  -there is no equivalent to the moving behavior
• Notes:
  -This command works two ways:
  -mv filename filename works like a rename in DOS, the file's name is changed
  -the original file will be gone
  -mv filename directory actually moves the file into the directory and kills it from the original directory

man - Manual

• The on-line help
• DOS equivalent:
  -help in ver. 5.0 and later of DOS
• Notes:
  -man topic opens up the manual page for the topic
  -the man pages can be obscure, but they contain a wealth of information
  -if man topic didn't work, try man -k topic
  this tells the man engine to search for a keyword

chmod - Change mode

• Changes the ownership settings of your file or directory
• Notes:
  -These settings let you do whatever you want to your files
  -When you want to make certain things accessible to others, you must change the persmissions
  -You will want to do this for your web documents

Permission Settings

• The three types of people:
  - me
  - group
  - others
• The three settings:
  - read
  - write
  - execute (run if it's a program, go through if it's a directory)

Interpreting Permissions

• I can do anything
• My group can read and write, but not execute
• Everyone else can only read it