Lab46 Wiki

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
<WRAP centeralign round box>
<WRAP><color red><fs 200%>Corning Community College</fs></color></WRAP>
<WRAP><fs 150%>CSCS1730 UNIX/Linux Fundamentals</fs></WRAP>
</WRAP>

~~TOC~~

======Project: THE PUZZLEBOX======

=====Errata=====
Typos and bug fixes:

  * On the last step (Action 2), the following command is requested of you:
    * cat results | mail -s "[PROJECT: the puzzle box]" wedge $USER
  * This apparently doesn't work all the way (i.e. you will not receive the e-mail, but I will). Try the following fix:
    * cat results | mail -s "[PROJECT: the puzzle box]" wedge **${USER}@offbyone.lan**

=====Objective=====
To become familiar with another useful utility, and to develop some basic debugging/diagnostic abilities.
=====Background=====
The filetype of a file can be extremely important when determining what application is used to open it.

Most of the time a file is named correctly, for instance a file ending in **.c** can be assumed to be the source code of a C program, or **.gz** to be a gzipped file.

With the **dircolors**(**1**) utility colorizing specific files, it is further assuming that files which end in **.mpg** are really MPEG files and colors them accordingly, and the same for **.zip** files, etc.

In other operating systems, a file's extension determines what application is used to open the particular file. If a file that ends in **.mp3** is really a **.png** file, the default MP3 player is going to have difficulties.

Sometimes files are not always named properly, either due to a web browser mangling an extension or for whatever reason. When a file is more than meets the eye, we must rely on the various tools available to use to determine what in fact it is.

====The file utility====

In UNIX there is a nifty little utility called **file** that attempts to determine the actual type of a file by checking a series of properties. From the **file**(**1**) man page:

There are three sets of tests, performed in this order:

  - filesystem tests,
  - magic number tests,
  - and language tests.

The first test that succeeds causes the file type to be printed.

A //filesystem// test checks to see if the file is non-ordinary (such as a socket, symbolic link, or other special file).

The //magic number// test is a check of files conforming to existing fixed formats, typically by examining the file at the binary level. If using a hex editor, you will find that **.gz** files should always start with the same sequence of hexadecimal values.

Finally, if the file is determined to be a simple ASCII file, it will attempt to analyze whether or not it conforms to some language (ie C source code vs. an HTML document).

Note that **file** is not always perfect, but for most cases will get the job done. Try checking files in your home directory or elsewhere on the system and see the results.

Refer to the **file**(**1**) manual page or your textbook for more information.

=====Practice=====
For this project, files are located in the **projects/puzzlebox/** subdirectory of the UNIX Public Directory.

^    ^|Do the following, and discuss the results in your Opus:|
| ^  a.|Copy **file.txt** into your home directory.|
|:::^  b.|Using **file**(**1**), what type of file does this appear to be?|
|:::^  c.|View the contents of this file using **cat**(**1**). Is it what it appears to be?|
|:::^  d.|Using **gzip**(**1**), compress this file with default compression. What does **file**(**1**) say?|
|:::^  e.|Uncompress the file, and recompress using arguments for fastest (not highest) compression. What does **file**(**1**) report now?|

As in many puzzles, one's visual comprehension of the scenario plays a vital role. Where something doesn't necessarily meet the eye, or is not behaving as you would expect- just try reading any messages or output. Sometimes the clues are right under your nose.

=====Procedure=====

Try your hand at the following activity, where things are not necessarily as they should be:

  * Locate the file **puzzle.txt** and copy it into your home directory.

Being a file that ends in **.txt**, you might try opening it in a text editor (or simply using the **cat**(**1**) utility.

Does it appear to be a text file?

  * Use the **file**(**1**) utility to determine the actual file type.
  * Based on the output of file, react as appropriate to unravel this puzzle in order to find some plain text directions that will instruct you how to finish this project.

As is the case many investigations, just observing how things behave can lead to recognition of an object's true state, or the recognition of a pattern, which can be used to solve the task at hand.

=====Submission=====
To successfully complete this project, you must follow the directions located in a readable file at the conclusion of this project. Until you encounter it, you are not yet finished (hint).

You should get some sort of confirmation indicating successful submission (actually, two) if all went according to plan. If not, check for typos and or locational mismatches.
Lab46 Wiki

User Tools

Site Tools

Page Tools
