August 31 --- Class 1  --- Introduction, UNIX Basics

Handouts:
	Syllabus
	Student Survey
	Axis Manual
	AWK tutorial

Activities:
	Setup accounts on nations cluster
		Use web page on class syllabus.  Requires network ID, password
	Introduction to desktop
		When you log in there should be a strip of icons at the bottom
		of the screen.  If you click on any upward pointing arrows
		you will get a menu with applications you can choose.
		On the right you will find one that can launch a help brower
		or introduction to the desktop.
		Work though as much of this tutorial as required.
	Logging out
		To log out, select the exit button from the tool bar.

	Modify path variable
		Executables for class exercises will appear beneath my home 
		directory in a subdirectory ~sg/bin
		To add this directory to your path, look for the first
		line in your ~/.cshrc file that starts with
		set path
		Add ~sg/bin just before the closing parenthesis


	Setting DISPLAY and permissions

		One of the wonderful things about the X Windows system is
		that it lets you pop up a window on a machine different from
		the one on which the program creating the windoe is running.
		If you make a beautiful graph you can show it to a friend in
		Alaska by setting the DISPLAY to be the computer in Alaska
		your friend is sitting in front of.  However, before we try
		that, the first thing is to make sure that you can display a
		graph on your own computer.

		This command may display a blank graph on your screen:

		axis </dev/null |plot -T x

		If you get the complaint: axis: Command not found., then the
		directory that contains axis is not in your path.  On the 
		Nations cluster, 
		/usr/local/bin/axis </dev/null | /usr/local/bin/plot -T x
		will avoid the problem of not having axis or plot in your path.

		If you don't get a graph at this point, it is either because
		your DISPLAY environment variable is not correctly set, or you
		do not have permission to create a window on your screen.

		The variable DISPLAY tells the application where to show the
		window.  That is, the DISPLAY can be set to your own computer,
		or to your friend's computer in Alaska.

		To find out the current value of the DISPLAY variable type:

		printenv DISPLAY

		To tell xplot on which machine to make the plot issue this
		command in the window where you will issue the axis command:
		  setenv DISPLAY workstation:0.0
		For example:
		  setenv DISPLAY sioux:0.0

		The next issue is whether the computer on which you wish to
		display the window has granted permission for you to display
		a window.

		The person (probably you) who is working at the console of 
		the workstation where you want the window displayed must
		issue the xhost command to allow xplot to open a window on
		its screen.  Here is an example:
		  xhost + sioux
		This allows X processes running on sioux to open windows at
		whichever machine has been issued the above command.

		If you want to display a window on your friend's computer in
		Alaska, yuor friend in Alaska must issue the xhost command on
		the computer he or she is using.  For example, the person in
		Alaska types:

		xhost + sioux.ucs.indiana.edu

		to allow sioux.ucs.indiana.edu to display a window on the
		computer in Alaska.

		If you find that you have to issue these commands every time
		you log on to display a graph, you might want to automate
		the process as described in the next paragraph.  On many
		systems, you might find that you do not need to do this.
		Also, if you use ssh to connect to a remote system, you might
		find that things are automatically set up so the DISPLAY and
		permissions are set up.  In fact, some oranizations now have
		"firewalls" to protect their networks what will stymie your
		efforts to set the DISPLAY.  So, when you start using a new
		machine, just try to display a graph or an xterm and see if
		you succeed before you start setting the DISPLAY or running
		xhost.

		You might want to do the above operations automatically every
		time you log in.  If so, to your .login file add:
		   setenv DISPLAY `hostname`:0.0
		   xhost + `hostname`
		
		If you plan to log in from elsewhere and display graphs
		remotely, you might want to add an alias like this to your 
		.cshrc file:
		   alias dcampy    'setenv DISPLAY campy:0'
		This would only work if campy's full name is 
		campy.ucs.indiana.edu, since the nations cluster is part of
		ucs.indiana.edu.  If you want to display on a physics 
		machine, give the full name of the machine.

		This is not the most enjoyable way to start a course in
		computational physics, but once you get things set up correctly
		you will reap the benefits for the rest of the semester and
		beyond.