Updated: 2017-05-31 12:12 EDT

1 Due Date and DeliverablesIndexup to index

Do not print this assignment on paper!

WARNING: Some inattentive students upload Assignment #8 into the Assignment #7 upload area. Don’t make that mistake! Be exact.

2 Purpose of this AssignmentIndexup to index

This assignment is based on your weekly Class Notes.

  1. Practice Quoting strings as command line arguments.
  2. Practice creating Hard Links and Symbolic Links to files.
  3. Practice with Permissions in Lab Worksheet #08 ODT
  4. Practice creating structure and changing Permissions.

Remember to READ ALL THE WORDS to work effectively and not waste time.

3 Introduction and OverviewIndexup to index

This is an overview of how you are expected to complete this assignment. Read all the words before you start working.

Complete the Tasks listed below on the Course Linux Server (CLS). Check your work using the given examples. Run a Checking Program to verify your work after you have run your own tests. Submit the output of the checking script to Blackboard before the due date.

Edit a file to fix the Quoting to protect all shell meta-characters.

Create some Hard Links and Symbolic Links to files.

Create directory and file structure with the given Permissions. Record the numeric (octal) permissions of each of the directories and files you create in the given record file.

3.1 The Source DirectoryIndexup to index

All references to the “Source Directory” below are to the directory ~idallen/cst8207/13w/assignment08/ and that name starts with a tilde character “~” followed by a userid with no intervening slash. The leading tilde indicates to the shell that the pathname starts with the HOME directory of the account idallen.

4 TasksIndexup to index

4.1 Set UpIndexup to index

  1. Create the following directory structure in your CLS HOME directory and record (for study purposes) the series of Unix commands you used to create it. Spelling and capitalization must be exactly as shown:

    `-- Assignments
        `-- assignment08

    This directory is the base directory for most pathnames in this assignment. Store your scripts and answers here.

  2. There is a Checking Program named assignment08check in the Source Directory on the CLS. Follow the instructions in the first two steps at the start of Checking Program to create a working symbolic link to this program.

4.2 Part A - Quoting exerciseIndexup to index

  1. Copy the script file test.sh from the Source Directory into your own file test.sh.

  2. Fix the Permissions on the file so that you can edit it and execute it and nobody else (group or other) has any permissions at all.

  3. Execute this script file and note that the output doesn’t match what is written in the file. Fix the Quoting inside the file so that every line appears exactly as written, blanks included, with no meta-character expansion by the shell. The correct output should give eight lines and look like this when you are finished:

    Where is the question mark after the file /etc/passwd?
    Is one also missing after /etc/group?
    The shell prompt is contained in the  $PS1  variable.
    This isn't appearing on my screen properly.  It's missing some quotes.
    This is also "missing" some quotes.  It is not "right" yet.
    This is also "missing" quotes.  It's output that doesn't make sense.
    This isn't working either.  The shell gives an error message.
    ***  This is a file to practice shell quoting.  ***

    The entire line of text on each line must be made into exactly one argument to echo. You can check your success by temporarily substituting the argv program from the Class Notes for the echo command. (You have to put the argv.sh program into the current directory under the name argv.sh and make it executable. Read the test.sh file for details on using this program. Remember to return the script to using only echo after your testing.)

    You’ll know you got it mostly right when you see this wc and sum output (but you’ll need to verify one-argument-per-echo using the argv.sh program):

    $ ./test.sh | wc
    8 77 461
    $ ./test.sh | sum
    39169   1  

    If your word count is correct but the number of characters is less, you probably failed to make the entire text one argument to echo on each line. You must use Quoting to hide all the blanks and special characters from the shell on each of the lines. The argv.sh program will tell you if you got it right.

  4. Run the script and redirect the output into file testout.txt

4.3 Part B - Linking exerciseIndexup to index

  1. In your assignment08 directory, create a sub-directory and an empty file ln/abcd0001.txt (no spaces), where the text abcd0001 is replaced by your own eight-character userid in the file name. NOTE: The sub-directory name is ln (two letters), not 1n (digit letter).

  2. For every unique character in your own eight-character userid, create a sub-sub-directory under ln with that single-character name.

    For example, the userid abca0151 would result in six unique sub-sub-directory names under the ln directory – one sub-sub-directory for each of the unique characters a, b, c, 0, 1, 5.

    Do this for your own userid, which means you may have more or fewer sub-sub-directories, depending on the letters and digits in your own userid.

  3. Inside each of those new sub-sub-directories, create a single Hard Link to the empty file from the first step. Keep the same file name as the original for each hard link. Use hard links, not symbolic links.

    Continuing the above example, the abca0151 user would hard link the original empty file name abca0151.txt into each of those six new sub-sub-directories, creating six additional names for the same file. Keep the same file name as the original for each hard link.

    Check the link counts on everything to make sure that you have created links to the same file and not made copies of the file. Use hard links, not symbolic links.

  4. For every lower-case letter directory name you created, create a short, relative Symbolic Link that is its upper-case equivalent. If you created directory a, then create symlink A that points to a so that both ls ln/a and ls ln/A give identical results. (You must use symbolic links, because you cannot make hard links to directories.)

  5. In every file you have just created, enter the following information, one name per line: Enter the names of the three common file system commands that are “directory only” commands that require permission only on the directory inode to work properly, and that do not require permissions on the file inode to work. The answer is three lines, one command name per line. (See your in-class notes for the three names I wrote on the board in Week 7 and Week 8.) The right answer has this format (three lines; three words; nine characters):

    $ wc abcd0001.txt
    3 3 9 abcd0001.txt

    Again, the text abcd0001 must be your own userid, in all cases. Hint: All the file names you created in this Part should be hard links to the same file.

4.4 Part C - A file to record your permissionsIndexup to index

You need to record the Permissions you set on each of the directories and files you create in the next Part, below. You will record these permissions by copying and editing a file that you get from your instructor. You can record each of the permissions as you create things step-by-step below, or you can record all of the permissions after you have finished, before you run the checking program.

  1. Copy the file record.txt from the Source Directory into your own file abcd0001.txt (no spaces) where the text abcd0001 is replaced by your own eight-character userid in the file name. This file copy should be located directly under your assignment08 directory.

  2. Fix the Permissions on the file so that you can edit it and nobody else (group or other) has any permissions at all.

  3. As you work on the next Part below, edit your copy of the file with vim. Replace each string of three underscores in the file with the correct three-digit numeric (octal) permission value that you record in the next Part below. Do not change anything else in the file. Note the word count at the bottom of the file. Your count must match exactly, at all times. If not, re-copy the file and start over.

4.5 Part D - Creating structure with permissionsIndexup to index

Do the Permissions section of Lab Worksheet #08 ODT before continuing. Record all your answers for later quizzes.

Now you will create some directories and files, then set the correct permissions on them. The permissions to set are described below.

Because you are applying Permissions to directories as a non-root user, be careful not to lock yourself out of directories by restricting permissions on them too soon. First, create all the file and directory structure from the top of the directory tree down, and then apply restrictive permissions afterward from the bottom of the tree upward.

If you don’t apply permissions last, from the bottom up, you will deny yourself permissions that will prevent you from entering some directories lower down. Assign permissions from the bottom toward the top.

  1. Create a directory named head under assignment08
    1. Directory head has no permissions for others. The group can use ls to see the content, but cannot create files or cd into the directory. The user has full permissions. Record the permissions for head in the Record file.
  2. Underneath directory head create three three-letter directories named: usr grp oth
    1. Directory usr has no permissions for group or other. The user can cd into it, but cannot create any new content nor use ls to see any files in it. Record the permissions.
    2. Directory grp has no permissions for user or other. The group can cd into it and use ls in it, but cannot create any new content. Record the permissions.
    3. Directory oth has no permissions for user or group. Others have full permissions. Record the permissions.
  3. Underneath directory usr create three two-letter files named: rd wr xc (You did create files, right?)
    1. None of the files have any permissions for group or other.
    2. File rd has read permission (only) for the user. Record the permissions.
    3. File wr has write permission (only) for the user. Record the permissions.
    4. File xc has execute permission (only) for the user. Record the permissions.
  4. Underneath directory grp create three two-letter files named: rw wx rx
    1. None of the files have any permissions for user or other.
    2. File rw has read and write permission (only) for the group. Record the permissions.
    3. File wx has write and execute permission (only) for the group. Record the permissions.
    4. File rx has read and execute permission (only) for the group. Record the permissions.
  5. Underneath directory oth create three three-character files named: rwx ??? *** (Some characters are meta-characters that are special to the shell and will need careful handling. See the Class Notes about Quoting.)
    1. None of the files have any permissions for user or group.
    2. File rwx has full permissions for other. Record the permissions.
    3. File ??? has no permissions for other. Record the permissions.
    4. File *** has only read permission for other. Record the permissions.

Remember to read all the words above about working from top to bottom and then from bottom to top in this Part.

4.6 When you are doneIndexup to index

That is all the tasks you need to do.

Check your work a final time using the Checking Program and save the output as described below. Submit your mark following the directions below.

5 Checking, Marking, and Submitting your WorkIndexup to index

Since I also do manual marking of student assignments, your final mark may not be the same as the mark submitted using the current version of the Checking Program. Answer the questions according to the assignment, not according to the incomplete set of mistakes detected by the Checking Program.

Summary: Do some tasks, then run the checking program to verify your work as you go. You can run the checking program as often as you want. When you have the best mark, upload the marks file to Blackboard.

  1. There is a Checking Program named assignment08check in the Source Directory on the CLS. Create a Symbolic Link to this program named check under your new assignment08 directory so that you can easily run the program to check your work and assign your work a mark. Note: You can create a symbolic link to this executable program but you do not have permission to read or copy the program file.

  2. Execute the above “check” program using its new symbolic link. (Review the Search Path notes if you forget how to run a program by pathname from the command line.) This program will check your work, assign you a mark, and display the output on your screen. (You may want to paginate the long output so you can read all of it.)

    You may run the “check” program as many times as you wish, to correct mistakes and get the best mark. Some tasks sections require you to finish the whole section before running the checking program at the end; you may not always be able to run the checking program successfully after every single task step.

  3. When you are done with checking this assignment, and you like what you see on your screen, redirect the output of the Checking Program into the text file assignment08.txt under your assignment08 directory. Use the exact name assignment08.txt in your assignment08 directory. You only get one chance to get the name correct. Case (upper/lower case letters) matters. Be absolutely accurate, as if your marks depended on it. Do not edit the file.

  4. Transfer the above assignment08.txt file from the CLS to your local computer and verify its contents. Do not edit this file! No empty files, please! Edited or damaged files will not be marked. You may want to refer to your File Transfer notes.

  5. Submit the assignment08.txt file under the correct Assignment area on Blackboard (with the exact name) before the due date. Upload the file via the assignment08 “Upload Assignment” facility in Blackboard: click on the underlined assignment08 link in Blackboard. Use “Attach File” and “Submit” to upload your plain text file.

    No word-processor documents. Do not send email. Use only “Attach File”. Do not enter any text into the Submission or Comments boxes on Blackboard; I do not read them. Use only the “Attach File” section followed by the Submit button. (If you want to send me comments about your assignment, use email.)

  6. Your instructor may also mark the assignment08 directory in your CLS account after the due date. Leave everything there on the CLS. Do not delete any assignment work from the CLS until after the term is over!

Use the exact file name given above. Upload only one single file of plain text, not HTML, not MSWord. No fonts, no word-processing. Plain text only.

Did I mention that the format is plain text (suitable for VIM/Nano/Pico/Gedit or Notepad)?


No marks are awarded for submitting under the wrong assignment number or for using the wrong file name. Use the exact name given above.

WARNING: Some inattentive students don’t read all these words. Don’t make that mistake! Be exact.


| Ian! D. Allen  -  idallen@idallen.ca  -  Ottawa, Ontario, Canada
| Home Page: http://idallen.com/   Contact Improv: http://contactimprov.ca/
| College professor (Free/Libre GNU+Linux) at: http://teaching.idallen.com/
| Defend digital freedom:  http://eff.org/  and have fun:  http://fools.ca/

Plain Text - plain text version of this page in Pandoc Markdown format

Campaign for non-browser-specific HTML   Valid XHTML 1.0 Transitional   Valid CSS!   Creative Commons by nc sa 3.0   Hacker Ideals Emblem   Author Ian! D. Allen