Computer Science 433
Programming Languages

Fall 2014, The College of Saint Rose

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In this assignment, you will learn (or refresh your memory about) some Unix commands, then implement a few of them in the language of your choice (I assume this will be Java for most of you). You may work alone or with a partner on this assignment.

The Unix Command Line

To get started, log into mogul.strose.edu. In your favorite editor, create a document in which you will answer the questions you find in this section. Start by putting your name at the top of this document.

GUIs are nice, but they can be slow to navigate and too restrictive for some purposes. For some of our examples and assignments, you will be working in a Unix environment and interacting with the system by typing commands at the Unix shell, or command line. When you log in, you will be presented with a prompt. This is your direct interface to issue commands to the operating system. When you type a command here, the shell will execute the command on your behalf, print out any results, then reissue the prompt.

Of course, the command line is useless if you don't know what commands it understands. You will learn about several important commands in this lab and many more throughout the semester. One of the most important is man - the Unix manual. Every Unix command has a manual page, including man. To see the manual page about man, type the command:

      man man

Navigating the Directory Structure

You have very likely used systems where files can be organized into folders. When accessing these kinds of structures from the command line, we usually refer to them as directories. Each program in a Unix system, including your shell, maintains the notion of a working directory. That is where the program will look for files unless instructed to do otherwise. You'll hear Unix users asking a question like "What directory are you in?" and the answer to this is your working directory.

When you first open a shell, your home directory is your working directory. The command pwd will instruct the shell to print your working directory.

You can also list the contents of your working directory with the command ls.

Other important operations to navigate and modify the directory structure are changing your working directory (cd), creating a new directory (mkdir), and removing a directory (rmdir).

Create a directory in your account for your work for this course (cs433 might be a good name), and a directory within that directory for this assignment (ps1 might be a good name).

In your shell window and in your home directory (note: you can always reset your working directory to be your home directory by issuing the command cd with no parameters), issue this command:

      uname -a > linux.txt

This will execute the command uname -a, which prints a variety of information about the system you are on, and "redirects" the output, which would normally be printed in your terminal window, to the file linux.txt.

Unix Commands

Identify the function of and experiment with these Unix commands (a few of which you have already used):

 
ls    cd      cp      mv     rm     mkdir   pwd
man   chmod   cat     more   grep   head    tail
ln    find    rmdir   wc     diff   tar     touch

Using appropriate commands from the above list, move the linux.txt file you created in your home directory into the directory you created for your work for this assignment.

Show that this has worked by issuing the following command from inside of your course directory:

	ls -laR > ls.out

Then move the file ls.out into your directory for this assignment.

All of these programs (except late.bas) can be run on mogul. Run each program at the command line and redirect its output to an appropriately-named file (e.g., "late.c.out" might be a good name for the C program's output). Hints: the C program can be compiled with gcc and the executable run directly, the Java program can be compiled with javac and run with java, the Perl and Python programs can be sent directly to their interpreters, which are installed as perl and python3, and the scheme program can be loaded into the MIT Scheme interpreter (scheme) by giving the command-line parameters "-load late.scm".

Create a "tar file" that includes your linux.txt, ls.out, and all of the "late" output files by issuing this command while in your directory that contains those files:

tar cvf unix.tar linux.txt ls.out ...

(Of course, you will replace the "..." with the list of files you created when you redirected the output of each of the "late" programs.)

This will create a file unix.tar in your directory. Transfer this to the computer you're working on with a secure copy program like WinSCP or FileZilla.

Implementing Some Unix Commands

Your programming tasks are to implement clones of 4 Unix commands in the language of your choice:

File Copy

 

cp filenameA filenameB - copy the contents of filenameA to a file named filenameB; see the Unix cp command.

Note: if you write this in Java, you would instead issue the command

java cp filenameA filenameB

but it should behave otherwise like the Unix cp command.

Display File Contents

 

cat [OPTION] filename - display the contents of filename, where the options can be either (or neither) of:

• -n - number all output lines
• -b - number nonempty output lines

See the Unix cat command.

Display Initial Lines of File

 

head [-n] filename - display the first n lines of filename, default is to display 10 lines if the flag is not specified. If the file has fewer than the requested number of lines, the entire file should be displayed.

See the Unix head command.

Word Count

 

wc filename - find the number of lines, words, and bytes (characters) in filename.

See the Unix command wc.

Write a separate program for each of the above (that is, do not have a single program that tries to perform all of the functionality).

Your code should be commented appropriately throughout. Please also include a longer comment at the top of your program describing your implementation. And, of course, it should include your name.

Submission

Before 11:59 PM, Wednesday, September 3, 2014, submit your work for grading. Create and submit a single archive file (a .7z or .zip file containing all required files) using Submission Box under assignment "PS1".

Grading

This assignment will be graded out of 40 points.