Updated: 2015-10-18 22:57 EDT
PATH
Do not print this assignment on paper!
- On paper, you will miss updates, corrections, and hints added to the online version.
- On paper, you cannot follow any of the hyperlink URLs that lead you to hints and course notes relevant to answering a question.
- On paper, scrolling text boxes will be cut off and not print properly.
15h00 (3pm) Tuesday March 10, 2015 (start of Week 9)
WARNING: Some inattentive students upload Assignment #7 into the Assignment #6 upload area. Don’t make that mistake! Be exact.
Do not print this assignment on paper! On paper, you cannot follow any of the hyperlink URLs that lead you to hints and course notes relevant to answering a question.
This assignment is based on your weekly Class Notes.
.bash_profile
and .bashrc
$PATH
.Remember to READ ALL THE WORDS to work effectively and not waste time.
This is an overview of how you are expected to complete this assignment. Read all the words before you start working.
For full marks, follow these directions exactly.
You will create file system structure in your CLS home directory containing various directories and files. You can use the Checking Program to check your work as you do the tasks. You can check your work with the Checking Program as often as you like before you submit your final mark. Some task sections below require you to finish the whole section before running the Checking Program; you may not always be able to run the Checking Program successfully after every single task step.
When you are finished the tasks, leave the files and directories in place on the CLS as part of your deliverables. Do not delete any assignment work until after the term is over!
Assignments may be re-marked at any time on the CLS; you must have your term work available on the CLS right until term end.
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. I do not guarantee that any version of the Checking Program will find all the errors in your work. Complete your assignments according to the specifications, not according to the incomplete set of the mistakes detected by the Checking Program.
All references to the Source Directory below are to the CLS directory ~idallen/cst8207/15w/assignment07/
and that name starts with a tilde character ~
followed by a user name with no intervening slash. The leading tilde indicates to the shell that the pathname starts with the HOME directory of the account idallen
(seven letters).
You do not have permission to list the names of all the files in the Source Directory, but you can access any files whose names you already know.
You must keep a list of command names used each week and write down what each command does, as described in the List of Commands You Should Know. Without that list to remind you what command names to use, you will find assignments very difficult.
Do a Remote Login to the Course Linux Server (CLS). All work in this assignment must be done on the CLS.
Set your PS1
shell prompt.
CST8207-15W
directory in your CLS HOME directory.Assignments
directory in the CST8207-15W
directory.assignment07
directory in the Assignments
directory.Hint: You can create the entire directory tree above using one single command.
This assignment07
directory is called the Base Directory for most pathnames in this assignment. Store your files and answers in this Base Directory, not in your HOME directory or anywhere else.
Run the Checking Program to verify your work so far.
You need to understand Start-Up Files and how to use a text editor such as The VI Text Editor to do this task.
.bash_profile
.bashrc
Use a Linux text editor to create your .bash_profile
and .bashrc
files with the minimum suggested content described in Start-Up Files. These files do not exist yet; you must create them.
Do not set any options or aliases in your .bashrc
that you do not understand! If you don’t know the meaning of a setting, don’t use it. You can RTFM in the bash
man page for all BASH settings, and RTFM in command man pages to learn about options to commands.
Using the PS1
variable from Worksheet #2 HTML, set your prompt to include your user name, your computer name, and the basename of your current working directory. Put this setting (or one like it) in your .bashrc
file.
Your .bash_profile
must contain only one line. Your .bashrc
must contain at least two lines (not including comment lines).
I will be spot-checking your knowledge of your aliases and shell options. Students using aliases they don’t understand will experience much confusion trying to do future assignments. Only use aliases and shell options that you understand.
Verify that nothing prints on your screen after you enter your password when you run the non-interactive shell connection using ssh localhost true
as described in the section on Non-interactive shells and PS1:
$ ssh localhost true
*** COURSE LINUX SERVER ***
user@localhost's password:
$
For non-interactive commands to work properly, there must be no output on your screen after you enter your password using the above non-interactive command line using the true
command.
Your instructor will mark the .bashrc
and .bash_profile
files in your account after the assignment due date. Do not upload them to Blackboard. Leave them there on the CLS. Do not delete anything.
Run the Checking Program to verify your work so far.
Follow correct double-quoting procedures when expanding variables, as noted in Shell Variables.
You may find it convenient to make the Base Directory your current directory while you work on this task. (Be lazy: Choose a current directory that makes your pathnames as short as possible!)
You may use a text editor such as The VI Text Editor to create this file.
enviro.sh
Use the echo
command to display the value of the environment variable containing your userid. Put the command you use to do this into file enviro.sh
in the Base Directory. (Put in the command, not the output.) The file will contain one command line.
Use the echo
command to display the value of the environment variable containing your home directory. Append the command you use to do this to file enviro.sh
in the Base Directory. (Put in the command, not the output.) The file will contain two command lines.
Use the echo
command to display the value of the environment variable containing your assigned shell. Append the command you use to do this to file enviro.sh
in the Base Directory. (Put in the command, not the output.) The file will contain three command lines.
Use the echo
command to display the value of the environment variable containing your shell search path. Append the command you use to do this to file enviro.sh
in the Base Directory. (Put in the command, not the output.) The file will contain four command lines.
Assuming that enviro.sh
is in your current directory, use the sh
shell to run (execute) your script by typing sh -u enviro.sh
and the values of all four environment variables should display on your screen. (If enviro.sh
is in some other directory, use the appropriate pathname to it.)
To verify that you have used proper procedures for expanding variables inside your script, set the USER
variable to be a GLOB character temporarily and then run the script again like this (assuming that enviro.sh
is in your current directory):
$ USER='*' sh -u enviro.sh
Make sure that the first line of script output is the single GLOB character *
and not a list of file names. If you see a list of file names, re-read the first sentence of this task, above.
Add one or more shell comment lines to the end of the file, describing in your own words the use for or meaning of each of the four variables in your script. A shell comment line starts with a number sign (octothorpe, pound-sign, or hashtag) character #
, e.g.
echo "Hi there."
# This is a shell comment line. The shell will ignore it.
# This is another comment line. It starts with the # character.
Run the Checking Program to verify your work so far.
PATH
IndexYou must know how to use a text editor and understand how a shell uses a search PATH
to do this task.
You may find it convenient to make the Base Directory your current directory while you work on this task. (Be lazy: Choose a current directory that makes your pathnames as short as possible!)
pathcheck.sh
Use a text editor to create a file named pathcheck.sh
under the Base Directory. This file will contain these four command lines:
PATH
variable to include the Source Directory for this assignment appended at the (right) end of the path. Append to the existing PATH
variable, as shown in the course notes.echo
the new value of PATH
onto your screen. Follow correct double-quoting procedures when expanding variables, as noted in Shell Variables.assignment07check
(the basename of the Checking Program), which it will do using the modified PATH
you set at the top of the script. No slashes should appear in this command name, so that the shell uses your modified $PATH
, set on the first line, to find it and run it. (Review how the shell search PATH
works.)After you have created your four-line shell script, enable execute permissions on the script file and then run (execute) it using these two command lines:
$ chmod u+x pathcheck.sh # all lower-case letters
$ ./pathcheck.sh
Remember how to make a file executable and run it from the current directory; you will need this again.
When you run the script, each of the four command lines in the script will execute, one after the other. The first line, setting the search path, should produce no output. There will be three outputs that come from the next three lines of the script:
PATH
.assignment07check
checking program and generate lots of output.Hints:
- You need to know how the shell uses the
PATH
variable to find and run commands.- You need to know how to append to
PATH
.- Remember to quote all variable expansions.
- If you see
command not found
output coming from commands inside the executing script, you have either spelled a command name incorrectly or have not correctly set the shell search path inside the script file. This script will only work if the shell searchPATH
is set correctly at the beginning (top) of the file.
Run the Checking Program to verify your work so far.
You must know how to use a text editor and understand how shells use Quoting to do this task.
You may find it convenient to make the Base Directory your current directory while you work on this task. (Be lazy: Choose a current directory that makes your pathnames as short as possible!)
goodquotes.sh
Copy the script file badquotes.sh
from the Source Directory into the current directory using the new name goodquotes.sh
as you copy it.
Enable execute permissions on the script file and run the script (as you did in the previous task).
Note that the output of running the script generates an error message and the lines output on the screen don’t match what is written in the script file. For example: many quotes are missing, GLOB characters and variables are expanding, and the spacing of the words is different.
Use a text editor to add Quoting inside the script file so that every line is fully quoted to appear onto your screen exactly as written in the file, blanks included, with no meta-character expansion by the shell. The correct ten lines of output should look exactly like this when you are finished, including all the extra spaces between some of the words:
Where is the question mark after the file /etc/passwd?
Is one also missing after /etc/group?
Do you see any *[square]* *[brackets]* in this line ?????
The BASH shell prompt is contained in the $PS1 variable.
This isn't appearing on my screen correctly. It's missing the quotes.
This is also "missing" all the quotes. It is "not right" yet.
This is also missing "quotes". It's output that doesn't make sense.
This line isn't working either. The shell gives an error message.
*** This is a file to practice shell quoting. Do you see this line? ***
Do you see this last line with the extra spaces ?
The correct script output (above) is exactly ten lines, 106 words, 624 characters and has a checksum of 61815 1
.
Hints:
You must edit the
goodquotes.sh
file to make the entire line of text on each line one single shell argument toecho
. Review how the shell finds arguments and how to use Quoting to hide shell metacharacters.You can check whether you have successfully created one single argument on each line by temporarily substituting the
argv.sh
program from the Class Notes for theecho
command.You can easily get a copy of the
argv.sh
program from the course notes on the CLS using thenewnotes
symbolic link you created in a previous assignment.Read the
goodquotes.sh
file for details on using an alias inside the quotes file to runargv.sh
. You have to put theargv.sh
program into the same directory asgoodquotes.sh
under the nameargv.sh
and make it executable. Remember to undo the alias and return the script to using onlyecho
after you finish your testing.If your line and 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. Theargv.sh
program will tell you if you got it right.
goodquotesout.txt
When the output of your edited script is correct, run the script and redirect the script output into file goodquotesout.txt
in your Base Directory (which should still be your current directory).
The file must contain exactly ten lines, 106 words, 624 characters and have a checksum of 61815 1
.
Run the Checking Program to verify your work so far.
You need to understand Symbolic Links to do this task.
check
check
in your Base Directory that links to the Checking Program in the Source Directory.Instead of typing the huge absolute pathname when you want to run the Checking Program, all you need to type is the short name of this symlink, which now points to the long pathname.
When in your Base Directory you can use your symbolic link ./check
to run Checking Program to verify your work so far.
You already created symbolic links to
oldnotes
andnewnotes
in a previous assignment. These (shorter) symbolic links let you access the course notes using much shorter pathnames. Sysadmin often create (shorter) symbolic links to long pathnames that they use frequently.
You need to understand Hard Links and Symbolic Links and to do this task.
ln/
abcd0001.txt
In your Base 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).
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
. (You can create multiple directories with one single command line.)
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.
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 you create. 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.
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.)
In every file you have just created in this section, 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, or read the course notes about links and inodes.) 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.
Hints: All the file names you created in this section should be hard links to the same file; you have very little editing to do. The three command names are all commands that are directory operations that manipulate file names; they don’t touch the file data and don’t need any permissions on the file data.
Use your symbolic link ./check
(created in the previous task) to run Checking Program to verify your work so far.
You need to understand Hard Links and Disk Usage to do this task.
Read this task all the way through, especially the Hints, before you delete anything, or else you will have to start over again.
For the next task, you will need to look up the copy option that means archive that preserves hard links (as well as all the other attributes) when you copy a directory (RTFM).
My DiskUse
DiskUse/
abcd0001
(where abcd0001
is replaced by your own userid). Copy, using the archive option, this directory into your Base Directory using the name My DiskUse
. You will know you got it right if your personal copy of the My DiskUse
directory has the same disk use summary (du -s
) as the one in the Source Directory.In your personal My DiskUse
directory, some of the files are hard links to each other. (If there are no hard links anywhere, you didn’t use the archive option to the copy command that preserves hard links. Delete everything and re-copy.)
Your personal copy of the My DiskUse
directory contains exactly four sub-directories, each of which contains many other files and sub-sub-directories. (If you don’t see four sub-directories under your copy of My DiskUse
, read all the words in the Hints again.) A recursive list of pathnames under My DiskUse
counts 302.
There are four levels of difficulty in this task, one for each of the four sub-directories in your personal My DiskUse
directory. Do the easy level first, followed by the medium level, followed by the hard level, followed by the ug1y level.
Read this task all the way through, especially the Hints, before you delete anything, or else you will have to start over again.
Locate the sub-directory of your personal My DiskUse
directory that contains the text easy
in the name. Make this your current directory and then follow steps A through C below:
Under the current directory, there is a directory named foo
.
Reclaim all the disk space used by the files under foo
by removing all the files under foo
and any hard links to those files. Some of those hard links may be to files in other sub-directories under the current directory; you don’t have to scan the whole file system to find the hard links. Read the Hints carefully before you remove anything.
Run the Checking Program to verify your work so far. See the Hints if you need to start over.
Locate the sub-directory of your personal My DiskUse
directory that contains the text medium
in the name. Make this your current directory. Repeat the steps A through C above.
Locate the sub-directory of your personal My DiskUse
directory that contains the text hard
in the name. Make this your current directory. Repeat the steps A through C above.
Locate the sub-directory of your personal My DiskUse
directory that contains the text ug1y
in the name. (Note carefully the strange spelling, which is not the same as ugly
.) Make this your current directory. Repeat the steps A through C above.
Hints: The current directory must be set as given above for each level.
Many of the files in the
foo
subdirectory in a level have more than one name. Some of those other names may be located in other subdirectories somewhere under the current level. (You don’t have to search the whole disk partition to find them.) The disk blocks for these files infoo
will not be freed until you find and remove all their names. Do not remove any names fromfoo
until you also know how to find and remove all the other names for these files. You will need to look at inode numbers to know which files in directoryfoo
are also named in the other directories. You read about how to do this in Disk Usage.Options to
ls
to display hidden names and nongraphic (unprintable) characters will be needed for the harder sections. Many names will need to be quoted to hide shell metacharacters (see Quoting).If you don’t get the right answer for a difficulty level, you can start over by re-copying all or part of your
My DiskUse
directory from where you originally got it in the Source Directory.If you make errors in this task and need to redo one of the four sections, you can remove and re-copy from the Source Directory just the sub-directory for that section. You don’t have to remove and re-copy the whole
DiskUse/
abcd0001
directory, since that would lose the work you did on the other sections.If you do want to remove your entire personal
My DiskUse
directory to start over, you will need to redo all four levels. If you are smart and rename the directory instead of removing it, you can salvage from the saved directory the parts of the task you have already done successfully, so you won’t have to redo those parts.If you find that you don’t own any of the files under your
My DiskUse
directory, and that you have no permission to remove any files, then you didn’t copy the files correctly. Delete everything and re-read and re-do that first step.
That is all the tasks you need to do.
Check your work a final time using the Checking Program below and save the standard output of that program into a file as described below. Submit that file (and only that one file) to Blackboard following the directions below.
When you are done, log out of the CLS before you close your laptop or close the PuTTY window, by using the shell exit
command:
$ exit
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 single file that is the output of the Checking Program to Blackboard.
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. I do not guarantee that any version of the Checking Program will find all the errors in your work. Complete your assignments according to the specifications, not according to the incomplete set of the mistakes detected by the Checking Program.
There is a Checking Program named assignment07check
in the Source Directory on the CLS. You can execute this program by typing its (long) pathname into the shell as a command name:
$ ~idallen/cst8207/15w/assignment07/assignment07check
You learn one way to make this shorter in the current assignment.
Execute the above Checking Program as a command line on the CLS. This program will check your work, assign you a mark, and display the output on your screen.
You may run the Checking Program as many times as you wish, allowing you to correct mistakes and get the best mark. Some task 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.
When you are done with this assignment, and you like the mark displayed on your screen by the Checking Program, you must redirect only the standard output of the Checking Program into the text file assignment07.txt
in your Base Directory on the CLS, like this:
$ ~idallen/cst8207/15w/assignment07/assignment07check >assignment07.txt
$ cat assignment07.txt
assignment07.txt
file name.YOUR MARK for
assignment07.txt
(containing the output from the Checking Program) from the CLS to your local computer.
YOUR MARK for
assignment07.txt
file from your local computer to the correct Assignment area on Blackboard (with the exact name) before the due date:
Use only Attach File on the Upload Assignment page. Do not enter any text into the Text Submission or Comments boxes on Blackboard; I do not read them. Use only the Attach File section followed by the Submit button. If you need to comment on any assignment submission, send me EMail.
You can revise and upload the file more than once using the Start New button on the Review Submission History page to open a new Upload Assignment page. I only look at the most recent submission.
You must upload the file with the correct name from your local computer; you cannot correct the name as you upload it to Blackboard.
You will also see the Review Submission History page any time you already have an assignment attempt uploaded and you click on the underlined assignment07 link. You can use the Start New button on this page to re-upload your assignment as many times as you like.
You cannot delete an assignment attempt, but you can always upload a new version. I only mark the latest version.
Your instructor may also mark files in your 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!
I do not accept any assignment submissions by EMail. Use only the Blackboard Attach File. No word processor documents. Plain Text only.
Use the exact file name given above. Upload only one single file of Linux-format plain text, not HTML, not RTF, not MSWord. No fonts, no word-processing. Linux plain text only.
NO EMAIL, WORD PROCESSOR, PDF, RTF, or HTML DOCUMENTS ACCEPTED.
No marks are awarded for submitting under the wrong assignment number or for using the wrong file name. Use the exact 16-character, lower-case name given above.
WARNING: Some inattentive students don’t read all these words. Don’t make that mistake! Be exact.
READ ALL THE WORDS. OH PLEASE, PLEASE, PLEASE READ ALL THE WORDS!