Frequently Asked Questions

When and where are the TA's office hours?
This will be established in the first class-day.

If this is not done feel free to make an appointment by mailing me at rus@silicon.weeg.uiowa.edu. I'm available most any time.
I need emacs! I need gnuplot! I need gr_osview! How can I run X Windows System programs remotely on silicon?
There are two steps involved:
1. Tell the machine at which you are sitting that silicon is allowed to display there. While logged into your local machine, type:
```
	xhost silicon.weeg
```
2. Tell silicon where you are. To do this, set the DISPLAY environment variable to the machine at which you are sitting. For example, say you're using ant.cs. While logged into silicon, type
```
	export DISPLAY=ant.cs:0
```
  if using ksh, or
```
	setenv DISPLAY ant.cs:0
```
  if using csh or tcsh.
Note that if you have multiple shells open to silicon simultaneously, you must do step 2 for each shell from which you want to run a graphical program.
I'm tired of typing "xhost blah blah" and "export DISPLAY blah blah". How can I automate this?
You may put
```
	xhost silicon.weeg
```
in the .login of a csh account or the .profile of a ksh account. This should work from any CS or ICAEN account. Note that doing this will allow anyone to display graphical programs on your terminal, even if you aren't logged into silicon. There is supposed to be a way to specify "csf123@silicon.weeg" but I haven't been able to get it to work.

Upon login, ksh keeps sets an environment variable which points back to the machine at which you are sitting. It's called REMOTEHOST. You may automatically set DISPLAY in your .profile on silicon by copying the value of this variable into DISPLAY.
```
	export DISPLAY=$REMOTEHOST:0
```
or
```
	setenv DISPLAY ${REMOTEHOST}:0
```
for ksh or csh, respectively.
My program exceeded it's CPU limit and dumped core!!! BLARGH???
This info is given numerous places and I'm sure you all know the answer already, but I'll include it here for the sake of completeness.
- Using ksh
```
	ulimit -S -a
```
  will show you all your limits and
```
	ulimit -S -t #
```
  will let you set your CPU time limit. For example,
```
	ulimit -S -t 120
```
  will set it to 2 minutes.
- Using csh
```
	limit
```
  will show you all your limits and
```
	limit cputime #
```
  will let you set your CPU time limit. For example,
```
	limit cputime 120
```
  will set it to 2 minutes.
I want to use the arrow keys in my shell. How do I set it up?
This solution applies to ksh only.

This is an interesting problem and I don't know an ideal solution to it. You need to set up some aliases. For example, type
```
	alias __A=Control-p
	alias __B=Control-n
	alias __C=Control-f
	alias __D=Control-b
```
to map the arrows up, down, left and right to the control keys for previous, next, forward and back. The problem is, of course, if you type Control-b on the command line, the cursor will simply jump back, as it is supposed to do.

The solution is to put these lines in your .kshrc using emacs or vi.
- Using emacs, type
```
	alias __A=Control-q Control-p
	alias __B=Control-q Control-n
	alias __C=Control-q Control-f
	alias __D=Control-q Control-b
```
  The "Q" stands for "quote" and may be used to insert any control character into any file.
- Using vi, type
```
	alias __A=Control-v Control-p
	alias __B=Control-v Control-n
	alias __C=Control-v Control-f
	alias __D=Control-v Control-b
```
  The "V" stands for "verbose" and it works the same as emacs' "Q".
A note to vi users: if you have your EDITOR environment variable set to vi, then ksh will be in vi mode. Control-p, n, f and b will have no effect and the above info is useless. The consolation is that, if you're a vi user, you're probably already used to moving the cursor around with h, j, k and l which work fine in ksh, so the above discussion is moot.
What's the difference between .kshrc and .profile and .cshrc and .login? What do I put in each?
If you're using ksh, then you need a .kshrc and a .profile. If you're using csh or tcsh, then you need a .cshrc and a .login. The .kshrc and .cshrc serve the same purpose and the .profile and .login serve the same purpose.

Your .kshrc/.cshrc is there to configure your shell. Use it to set any environment variables that you may need, create aliases, change your prompt, or turn shell options on and off.

Your .profile/.login is there to execute commands and programs at login time. Use it to automatically check your mail, enable talk messages, show you the system's status, or whatever else you might want. An important distinction is that the .profile/.login is only referenced by interactive shells, i.e. when you log in. If you execute a shell script, .profile/.login is not referenced by the shell that executes it. The .kshrc/.cshrc is referenced in either case.
Did you know that there's a big glaring omission, error, or typo in this FAQ?
No, I didn't. If you have more questions or if you've found problems with this file please alert me by sending mail to csi000@silicon.weeg.uiowa.edu.

FAQ develpoed by Bob Kooima during Fall Semester 1998 .