CSCI 3291 (Current Topics -- Unix System Administration), Fall 2004:
Homework 1

Assigned:

September 27, 2004.

Due:

October 4, 2004, at 5pm.

Credit:

40 points.

Reading

Be sure you have read chapters 1, 4, and 5 in the textbook.

Problems

Answer the following questions. You may write out your answers by hand or using a word processor or other program, but please submit hard copy, either in class or in my mailbox in the department office. Answers to most questions will involve experimentation on a Unix or Linux system. You are free to use any appropriate system; if you use something other than Fedora Core Linux please tell me what.

1. (10 points) From its behavior, bash appears to maintain some sort of command history for each user, which is retained from one login to the next. Where does it keep this history? How many commands are saved? (The answer to one or both questions might be ``it depends'', in which case tell me what it depends on and whether/how you could change it.) (Hint: Read the appropriate man page.)

2. (10 points) A friend tells you that there are man pages available for all the common C library functions. But when you type man printf, you get a man page describing what seems to be a shell command rather than a function. Is there also a man page for the C function? If so, how do you read it?

3. (10 points) Suppose you have a directory foo that currently only you can access (for reading, writing, etc.). How could you make foo and all its subdirectories (and their subdirectories, etc.) read-accessible to all users, without changing more permissions than you need to (i.e., no fair just giving all the files and directories permissions of 777)? (Hint: With the GNU version of the appropriate command, this can be done with a single command. You might need to read the info page to find all the appropriate options.)

Programming Problem

Do the following programming problem. Turn in your code (shell script) by sending mail to bmassing@cs.trinity.edu, with your script as an attachment. Please use a subject line that mentions the course and the assignment (e.g., ``csci 3291 homework 1''). You can develop your script on any system that provides the needed functionality, but I will test it on one of the department's Fedora Core 2 machines, so you should probably make sure it works in that environment before turning it in.

1. (10 points) Write a shell script that takes one command-line argument, a username, and prints the number of processes owned by that username. (The script should do something reasonable if no argument is supplied -- either print an error message or print the total number of processes in the system.)