Chapter 10 Assignment

1.) What series of commands starts a child csh shell, determines the current port, and then examines the processes currently running on that port?
sh
tty
ps -t 'port'

2a.) What signal quits a process? 3
b.) What signal interrupts a process? 2
c.) What are the differences between the two? Signal 2 tells the process to exit using its ending process, signal 3 forces the process to end.
d.) When should you use kill -9? You should use this when all else fails. Processes need to go through the ending tasks so you should only use this if nothing else is working.

3.) What command would you use to bring the vi editor to the foreground?
fg

4.) What is the command that you would use to kill the more process?
kill -2 more 'port'

5.) What is the command you would use to get this listing?
ps

6.) Consider the following scenario: You log on to your sysetm on tty223. The system starts a csh for you that has a PID of 1056. Then you start a shell script(the script is executed by a sh with a PID of 1080) that in turn executes who(a PID of 2020).

a.) What is the PPID of the who process? 1080
b.) What is the PPID of the process executing the script? 1056
c.) With the information provided, can you determine with what tty the who process is associated? No

System Security

Computer security is something that should be important to everyone in the age of the Internet. In the days of "boards" that computers connected to there were not a whole lot of people that could do damage to your system from the outside. Mostly you just had to worry about your own ineptness accidentally messing something up. Now that there are literally hundreds of millions of people on-line there is a lot more that can cause you grief. Of course with the advancement of these problems there have also been advancements in security for your computer.

Whether it is one that comes with your operating system, or one that comes with anti-virus softerware, a firewall can go a long way towards acheiving piece of mind. Firewalls are designed to prevent unwanted intrusions into your system, and depending on how high the sensitivity on it can really help prevent your system from messed up from the outside.

Having a good anti-virus program is a must today. If you connect to the internet without one you are opening your machine up to all types of problems such as worms, viruses, trojans, and spyware. A good program can prevent these from getting onto your system, and can also help prevent you from accidently opening something you shouldn't.

Even with firewalls, and anti-virus softerware, the best security is common sense. If you open email from someone you don't know you are opening your system to attack. Another thing to avoid are websites from unknown publishers. Just because something seems like it may be safe does not mean that it is. The world is full of malicious people that are just waiting to surprise the unsuspecting Internet surfer with a damaging virus.

Shelling out instructions

To get the general idea of what a shell is, I think it is best to think of an egg. You have the outside shell that gives you access to the inside parts of the egg. When applying this to computer terms it is very similar. The shell part of the operating system gives you access to the usable parts. By this I mean that you are able to activate your programs and such using the shell.

The most common shell now is most likely Windows Explorer. It has turned what was once a bit complicated in early versions of Windows into an easy to use operating system that can be found in use around the world. Windows first shell was a program manager, that allowed you to group together programs for easy access, but it was hard to use unless you knew what you were doing.

The first shell that I can remember using is the DOSShell. In the old DOS command line interface in the later versions you could type in dosshell and enter into a file manager that gave you easier access into the programs you were trying to use.

Another shell that I had the pleasure of working with was called GEOWORKS. I don't think it was a very well, although it was one of the easiest shells I ever used. GEOWORKS allowed you to make buttons that you could click on to go directly into the programs you wanted to use. There was no such thing as double-clicking, and you were able to set it up the way you wanted.