% CST8207 Assignment 06 – quoting, search PATH, disk usage, hard and soft links % Todd Kelley, Ian! D. Allen – - [www.idallen.com] % Fall 2014 - September to December 2014 - Updated Thu Oct 30 12:02:23 EDT 2014 Due Date and Deliverables ========================= > **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. - **Due Date**: `12h00 (noon) Monday October 27, 2014 (start of Week 9)` - You have more than one week to do this assignment, but your next assignment will be available soon and will overlap this assignment. Start work on this now! Don’t delay! - Late assignments or wrong file names may not be marked. Please be accurate and punctual. - **Available online** - Version 1 – 13:45 Thursday October 16, 2014 - Version 2 – 22:50 Monday October 20, 2014 (corrected name of goodquotesout.txt file) - Version 3 – 02:10 Wednesday October 22, 2014 (re-formatted some Hints) - **Prerequisites** - All [Class Notes][hyperlink URLs] since the beginning of term. - All your previous [Assignments] and [Worksheets]. - An ability to **READ ALL THE WORDS** to work effectively. - **Deliverables** 1. One plain text file uploaded to Blackboard according to the steps in the [Checking Program] section below. 2. Directory structure created and left for marking on the [Course Linux Server] (**CLS**).\ **Do not delete any assignment work from the CLS until after the term is over!** **WARNING:** Some inattentive students upload Assignment #6 into the Assignment #5 upload area. Don’t make that mistake! Be exact. Purpose of this Assignment ========================== > **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]. 1. Study shell quoting and fix the quoting in a broken shell script. 2. Work with your search `$PATH`. 3. Examine how hard links work with disk usage. 4. Create hard links and soft (symbolic) links. Remember to **READ ALL THE WORDS** to work effectively and not waste time. Introduction and Overview ========================= 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. 1. Complete the **Tasks** listed below. 2. Verify your own work before running the **Checking Program**. 3. Run the **Checking Program** to help you find errors. 4. Submit the output of the **Checking Program** to Blackboard before the due date. 5. **READ ALL THE WORDS** to work effectively and not waste time. 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 these files and directories in place on the CLS as part of your deliverables. **Do not delete any assignment work from the CLS 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. The Source Directory -------------------- All references to the “Source Directory” below are to the CLS directory `~idallen/cst8207/14f/assignment06/` 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` (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. Tasks ===== - Do the following tasks in order, from top to bottom. - These tasks must be done in your account on the [Course Linux Server]. - **READ ALL THE WORDS!** and do not skip steps. - Run the [Checking Program] to grade your work, then upload the file to Blackboard. - Your instructor will also mark on the due date the work you do in your account on the CLS. Leave all your work on the CLS and do not modify it. - **Do not delete any assignment work from the CLS until after the course is over.** Set Up – The Base Directory on the CLS -------------------------------------- 1. Do a [Remote Login] to the [Course Linux Server] (**CLS**) from any existing computer, using the host name appropriate for whether you are on-campus or off-campus. 2. Make the CLS directory `~/CST8207-14F/Assignments/assignment06`, in which you will create the files and scripts resulting from the following tasks. > **This `assignment06` directory is the [Base Directory] for most > pathnames in this assignment. Store your files and answers in this Base > Directory.** Run the [Checking Program] to verify your work so far. Quoting Exercise – Easy Version ------------------------------- You must know how to use a text editor and understand how shells use [Quoting] to do this task. 1. Make the [Base Directory] your current directory. 2. Copy the script file `badquotes.sh` from the [Source Directory] into the current directory using the new name `goodquotes.sh` as you copy it. 3. Enable execute permissions on the script file and then run it using these two command lines: $ chmod ugo+x goodquotes.sh $ ./goodquotes.sh Remember how to make a file executable and run it from the current directory; you will need this again. 4. Note that the output of running the script generates an error message and doesn’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 `echo` 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/group? Is one also missing after /etc/passwd? Do you see *[square]* *[brackets]* ? The shell prompt is contained in the $PS1 variable. This isn't appearing on my screen properly. 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 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? 5. When the edited script output is correct, run the script and redirect the script output into file `goodquotesout.txt` in your [Base Directory] (the current directory). **Hints:** A. You must edit the `goodquotes.sh` file to make the entire line of text on each line *one* single shell argument to `echo`. Review how the shell finds [arguments] and how to use [Quoting] to hide shell metacharacters. B. 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 the `echo` command. You can easily get a copy of the `argv.sh` program from the course notes on the CLS using the `newnotes` symbolic link you created in a previous assignment. Read the `goodquotes.sh` file for details on using an alias inside the quotes file to run `argv.sh`. You have to put the `argv.sh` program into the same directory as `goodquotes.sh` under the name `argv.sh` and make it executable. Remember to undo the alias and return the script to using only `echo` after you finish your testing. C. Once you have created a non-empty `goodquotesout.txt` file, the [Checking Program] will tell you the expected word count. 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][arguments] 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. Run the [Checking Program] to verify your work so far. Working with your search `PATH` ------------------------------- You must know how to use a text editor understand how a shell uses a [search `PATH`] to do this task. 1. Use a text editor to create a file named `pathcheck.sh` under the [Base Directory]. This file will contain exactly four lines of text: 1. The first line must set the [shell search `PATH`][search `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. 2. The second line must safely `echo` the new value of `PATH` onto your screen. Follow correct double-quoting procedures when expanding variables, as noted in [Shell Variables]. 3. The third line must be the command that shows the host name (computer name) of the CLS machine (the same name as seen in the shell prompt). 4. The fourth line must have the shell find and execute a command named `assignment06check` (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`][search `PATH`] works.) 2. After you have created your four-line shell script, make the file executable, and then run it. (Use the same method as you did with the quotes script in a previous task, above.) 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: 1. The script should first display on your screen the output from the second line of the script: the modified `PATH`, 2. then the name of the machine should display, 3. and finally the `assignment06check` checking program should start running. **Hints:** A. You need to know how the shell uses the `PATH` variable to [find and run commands][search `PATH`]. B. You need to know how to [append to `PATH`][search `PATH`]. C. Remember to [quote all variable expansions][Shell Variables]. D. 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 search `PATH` is set correctly at the beginning (top) of the file. Run the [Checking Program] to verify your work so far. Four Disk Usage Exercises: easy, medium, hard, ugly --------------------------------------------------- You need to understand [Hard Links] and [Disk Usage] to do this task. 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). 1. After you have run the [Checking Program] at least once, you will find created for you in the [Source Directory] a disk usage directory named `DiskUse/`*abcd0001* (where *abcd0001* is replaced by *your own userid*). Copy, using the *archive* option, this directory into your [Base Directory] using the name `DiskUse`. You will know you got it right if your personal copy of the `DiskUse` directory has the same disk use summary (`du -s`) as the one in the [Source Directory]. Your personal copy of the `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, read all the **Hints**.) A recursive list of pathnames counts 302. There are four levels of difficulty in this task, one for each of the four sub-directories in your personal `DiskUse` directory. In your personal `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.) Read this task all the way through, especially the **Hints**, before you delete anything, or else you will have to start over again. There are four levels of difficulty. Do the **easy** one first, followed by **medium**, followed by **hard**, followed by **ugly**: 2. Locate the sub-directory of your personal `DiskUse` directory that contains the text `easy` in the name. Make this your current directory. A. Under the current directory, there is a directory named `foo`. B. 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. C. Run the [Checking Program] to verify your work so far. 3. Locate the sub-directory of your personal `DiskUse` directory that contains the text `medium` in the name. Make this your current directory. Repeat the steps **A** through **C** above. 4. Locate the sub-directory of your personal `DiskUse` directory that contains the text `hard` in the name. Make this your current directory. Repeat the steps **A** through **C** above. 5. Locate the sub-directory of your personal `DiskUse` directory that contains the text `ug1y` in the name. (Note carefully the spelling.) Make this your current directory. Repeat the steps **A** through **C** above. **Hints:** A. Many of the files in each `foo` subdirectory have more than one name. Those other names may be located somewhere else in the current directory, for each of the difficulty levels. (You don’t have to search the whole disk partition to find them.) The disk blocks for these files in `foo` will not be freed until you find and remove *all* their names. **Do not remove any names from `foo` 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 directory `foo` are also named in the other directories. You read about how to do this in [Disk Usage]. B. 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]). C. If you don’t get the right answer for a difficulty level, you can start over by re-copying all or part of the `DiskUse` directory from 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 `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. D. If you find that you don’t own any of the files under `DiskUse`, and that you have no permission to remove any files, then you didn’t **copy** the files correctly. Re-read that first step. Run the [Checking Program] to verify your work so far. Symlink to the Checking Program ------------------------------- You need to understand [Symbolic Links] to do this task. 1. Create a symbolic link named `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. Use your symbolic link `./check` to run [Checking Program] to verify your work so far. > You already created symbolic links to `oldnotes` and `newnotes` 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. Hard and Soft Linking exercise ------------------------------ You need to understand [Hard Links] and [Symbolic Links] and to do this task. 1. 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). 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`. (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. 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 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. 4. For every lower-case letter directory name you created, create a short, relative [Symbolic Link][Symbolic Links] 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 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][Hard Links] 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. When you are done ----------------- That is all the tasks you need to do. Check your work a final time using your symbolic link to the [Checking Program] and save the output as described below. Submit your mark following the directions below. Checking, Marking, and Submitting your Work =========================================== **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. > 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]. 1. There is a [Checking Program] named `assignment06check` 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/cst8207/14f/assignment06/assignment06check You learn one way to make this name shorter in one of the tasks of this assignment. 2. Execute the above `check` 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 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 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.** 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 `assignment06.txt` under your [Base Directory] on the CLS. Use that *exact* name. Case (upper/lower case letters) matters. Be absolutely accurate, as if your marks depended on it. - Do not edit the output file. Submit it exactly as given. - Make sure the file actually contains the output of the checking program! - The file should contain near the bottom a line starting with: `YOUR MARK for` - Really! **MAKE SURE THE FILE HAS YOUR MARKS IN IT!** 4. Transfer the above `assignment06.txt` file from the CLS to your local computer and verify that the file still contains all the output from the checking program. 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. - Do not edit the output file. Submit it exactly as given. - Make sure the file actually contains the output of the checking program! - The file should contain near the bottom a line starting with: `YOUR MARK for` - Really! **MAKE SURE THE FILE HAS YOUR MARKS IN IT!** 5. Upload the `assignment06.txt` file from your local computer to the correct Assignment area on Blackboard (with the exact name) before the due date: 1. On your local computer use a web browser to log in to Blackboard and go to the Blackboard page for this course. 2. Go to the Blackboard *Assignments* area for the course, in the left side-bar menu, and find the current assignment. 3. Under *Assignments*, click on the underlined **assignment06** link for this assignment. a) If this is your first upload, the *Upload Assignment* page will open directly; skip the next sentence. b) If you have already uploaded previously, the *Review Submission History* page will be open and you must use the *Start New* button at the bottom of the page to get to the *Upload Assignment* page. 4. On the *Upload Assignment* page, scroll down and beside *Attach File* use *Browse My Computer* to find and attach your assignment file from your local computer. Make sure the assignment file has the correct name on your local computer before you attach it. 5. After you have attached the file on the *Upload Assignment* page, scroll down to the bottom of the page and use the *Submit* button to actually upload your attached assignment file to Blackboard. 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. 6. **Verify that Blackboard has received your submission**: After using the *Submit* button, you will see a page titled *Review Submission History* that will show all your uploaded submissions for this assignment. Each of your submissions is called an *Attempt* on this page. A drop-down list of all your attempts is available. a) Verify that your latest *Attempt* has the correct 16-character, lower-case file name under the *SUBMISSION* heading. b) The one file name must be the *only* thing under the *SUBMISSION* heading. Only the one file name is allowed. c) No *COMMENTS* heading should be visible on the page. Do not enter any comments when you upload an assignment. d) **Save a screen capture** of the *Review Submission History* page on your local computer, showing the single uploaded file name listed under *SUBMISSION*. If you want to claim that you uploaded the file and Blackboard lost it, you will need this screen capture to prove that you actually uploaded the file. (To date, Blackboard has never lost an uploaded file.) You will also see the *Review Submission History* page any time you already have an assignment attempt uploaded and you click on the underlined **assignment06** 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. 7. 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!** -- | Todd Kelley, and | 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 [www.idallen.com]: http://www.idallen.com/ [hyperlink URLs]: indexcgi.cgi#XImportant_Notes__alphabetical_order_ [Assignments]: indexcgi.cgi#XAssignments [Worksheets]: indexcgi.cgi#XWorksheets__not_for_hand_in_ [Checking Program]: #checking-marking-and-submitting-your-work [Course Linux Server]: 070_course_linux_server.html [Remote Login]: 110_remote_login.html [Base Directory]: #set-up-the-base-directory-on-the-cls [Quoting]: 440_quotes.html [Source Directory]: #the-source-directory [arguments]: 150_arguments_and_options.html [`argv.sh`]: 440_quotes.html#using-argv.sh-to-count-command-line-arguments [search `PATH`]: 400_search_path.html [Shell Variables]: 320_shell_variables.html [Hard Links]: 455_links_and_inodes.html [Disk Usage]: 457_disk_usage.html [Symbolic Links]: 460_symbolic_links.html [Hard Link]: 450_file_system.html [File Transfer]: 015_file_transfer.html [email]: mailto:idallen@idallen.ca [Plain Text]: assignment06.txt [Pandoc Markdown]: http://johnmacfarlane.net/pandoc/