% CST8207 Week 10 Notes -- Shell Scripts: Command Substitution, integer arithmetic, exit status; Midterm Test #2 % Ian! D. Allen -- -- [www.idallen.com] % Winter 2019 - January to April 2019 - Updated 2019-03-21 01:45 EDT - [Course Home Page] - [Course Outline] - [All Weeks] - [Plain Text] Readings, Assignments, Labs, Tests, and ToDo ============================================ Read (at least) these things (All The Words) -------------------------------------------- 1. [Week 10 Notes HTML] -- this file -- **Read All The Words** 2. [Shell Scripts] -- executable lists of commands: `#!`, script header, command arguments and positional parameters: `$1`, `$2`, `$*`, `$@`, `$#` 3. [Command Substitution] -- interpolate stdout into a command line using `$(...)` or \`...\` 4. [Integer Arithmetic] -- shell script integer math: `expr`, `let`, `$((...))` 5. [Command Exit Status] -- variable `$?` 6. Next week: [Shell Script Debugging] -- using options `-v` and `-x` 7. Next week: [Shell Control Structures] -- if, then, else, test, `[...]`, for, while, case, break, continue, read, functions, &&, \|\|, errors 1>&2 8. [List of Commands] -- Command names you should know, listed by week 9. [Video Tutorials on Lynda.com] -- tagged by week number 10. [Linux and Sysadmin News in the World] Assignments, Quizzes, and Lab work this week -------------------------------------------- > **Reminder:** There are now two quizzes that you need to complete (five > times each) on Brightspace as part of your term Quiz mark. A third quiz > will be posted before the Final Exam. The Quizzes are *not* optional; see > the [Course Outline]. Check the due date for each assignment and put a reminder in your agenda, calendar, and digital assistant. Just like in the Real World, not all due dates are on the same days or at the same times. - Review last week. Did you do everything assigned last week? - Do [Worksheet #08 HTML] to prepare for [Assignment #09 HTML] -- setting permissions, mode, `umask`, personal web site - This assignment and material is *not* part of the second midterm test - [Assignment #11 HTML] -- tar, processes, syslog, crontab, at, mail, shell script - This assignment and material is *not* part of the second midterm test - OPTIONAL BUT HIGHLY RECOMMENDED: Read [The VI (VIM) Text Editor] and optionally do the bonus [Assignment #04 HTML]. Real Linux sysadmin all know how to use this text editor. - **Reminder:** You must actually use the VIM editor during the term to get full marks for this bonus assignment. Read All The Words. ### Worksheets Worksheets are preparation for your assignments. You can't do the assignments without having done the worksheets first, and you can't do the worksheets without having first read the Course Notes: 1. Read the web notes. (Please: **Read All The Words**) 2. Do the relevant Worksheet(s). 3. Do the relevant Assignment(s). Make notes from the worksheets on *how each command works*. What do the options used in the worksheets mean, for each command? (See the weekly [List of Commands].) Form a small study group to do the worksheets. Each person tries the example given, and you make sure you all get the same answers. Worksheets are not for hand-in; they are not worth marks; the assignments test your knowledge of the lectures and worksheets. > The worksheets are available in four formats: Open Office (ODT), PDF, HTML, > and Text. Only the Open Office format allows you "fill in the blanks" in > the worksheet. The PDF format looks good but doesn't allow you to type into > the blanks in the worksheet. The HTML format is crude but useful for quick > for viewing online. Do **NOT** open the Worksheet ODT files using any Microsoft products; they will mangle the format and mis-number the questions. Use the free Libre Office or Open Office programs to open these ODT documents. On campus, you can get a copy here: [Course Introduction: Install Libre Office]. Worksheet #06 is for the optional VIM Bonus Assignment (extra credit): - [Worksheet #06 HTML] -- *Optional* Bonus VIM Text Editor Practice - This is an *optional* worksheet for a BONUS assignment using `vim` - Optional command-line VIM tutorial: the `vimtutor` program on the CLS. - Bonus (optional) [Assignment #04 HTML] -- the VIM text editor - Read [The VI (VIM) Text Editor] Worksheet #08 is for [Assignment #09 HTML]. - [Worksheet #08 ODT] -- Linux file system permissions (modes) - This Worksheet is a prerequisite for [Assignment #09 HTML] - [Worksheet #08 PDF] -- PDF version - [Worksheet #08 HTML] -- HTML version - `chmod, ls -lid, umask` Worksheets prepare you for the upcoming assignments. Upcoming tests and exams ------------------------ This course has two midterm tests (10%, 15%) and one final exam (40%). > Note that your upcoming Midterm Test #2 is worth more than five assignments > put together. Don't spend all your time doing an assignment at the expense > of studying the [Practice Tests and Answers] for the Midterm Test. ![Bring your favourite marker to your test] Follow this link to see all your upcoming [Quizzes and Tests]. The dates are also posted on the [Course Home Page] and on [Brightspace CST8207]. For full marks, read the [Test Instructions] (all the words) **before** your midterm tests. 1. First Midterm test: Done. 2. Second Midterm test is THIS WEEK: 45 minutes; 8am Friday March 22 in your 50-minute lecture class in Week 10 -- THIS WEEK. 3. Final Exam: The date is now posted on ACSIS: Tuesday April 23 from 1pm to 4pm in T119. Midterm tests take place in your one-hour lecture class, not in your lab period. Notes from the Classroom ======================== - **Take notes in class!** Keep a pad open on your desk. - Don't forget to finish your five Brightspace quiz attempts for each of the Midterm 1 and Midterm 2 quizzes. There is a third quiz available to prepare for the Final Exam. Do at least five attempts in all three quizzes. - Regarding [Assignment #09][Assignment #09 HTML], [Assignment #11][Assignment #11 HTML], and [Assignment #12]: - Material in these assignments is **NOT** on the upcoming second midterm test. - Do not spend time doing these later assignments (3% each) at the expense of studying for your upcoming second midterm test (15%)! - Regarding world-writable files in your account: - Outside of the one directory in [Assignment #09][Assignment #09 HTML], you must not have any world-writable (writable by "other") files or directories in your account. - The checking program will deduct marks if it finds world-writable files. - See below. : *Research Matters / The Magic of Writing Stuff Down* -- Note taking is an effective memory and learning aid because it prompts students to think about their learning; it's more effective when done by hand; and young writers, even those with learning disabilities, aren't well served by moving too quickly to keyboarding. Commands Used ------------- > Keep a notebook with a [List of Commands] in it. > > - You need to write down yourself what each command *does*. > - Check the updated list of commands each week. > - I will check for this list in your lab periods. > - Bring your notes to class! Stop wasting time looking up commands. - Are you making notes from the worksheets on how each command works? - What do the options used in the worksheets mean, for each command? - Don't copy and use options that you don't understand! Finding world-writable files in your account -------------------------------------------- The assignment **Checking Programs** may issue this message: Number of world-writable pathnames in abcd0001 account: 1 ERROR: Sysadmin do not create files that anyone can overwrite. ERROR: See "Examples of uses of find" to find these files. ERROR(-1): Fix the permissions on these files Don't create files or directories that anyone ("other") can write, except the few required ones in the one [Assignment #09 HTML] `head` directory! You must look at all the files in your account to try to find these files or directories that you have created with "other" write permissions. You can find the files the hard way, using `cd` and `ls`, or you can do it the easy way using a recursive command to look for them: - To search the course notes for a text string, re-read section 4.5.1 of [Assignment #05 HTML], especially item #11 about searching for the text string `world-writable` in all the course notes. - You will be able to identify which course notes web page you should read to find the example showing how to find world-writable files. - Fix the permissions on your files. Remove write permission for "other". Your own personal web page on the CLS ===================================== This is part of [Assignment #09 HTML]. You can do it now, if you Read All The Words. - [Create your own web page!] - You will need to use `chmod 755` on your `public_html` directory. - Your web page will be visible on the Internet using a web browser to access URL `http://cst8207.idallen.ca/~``abcd0001` where *abcd0001* is replaced with your CLS userid. (There is a tilde character in that URL.) - Example: - View [all the Winter 17W class images] - View [all the Fall 17F class images] - View [all the Winter 18W class images] - View [all the Fall 18F class images] - View [all the Winter 19W class images] Who is using the VIM editor? ============================ This page may take a minute or two to load; be patient: [Who is using the VIM editor?] Tutoring ======== Many students find that hiring a personal tutor helps them get through the first term. Financial assistance is available. See the **Tutoring** heading in the [Course Introduction]. SSH and HTTP Attacks on the CLS =============================== You are not paranoid if they really are out to get you! See the [Week 03 Notes HTML] for command pipelines to count the ongoing attacks on the CLS. Locked out of the CLS ===================== When you are locked out, [follow the directions] in the notes to get your IP address re-enabled. ![Take Notes in Class] -- | Ian! D. Allen, BA, MMath - 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/ [Course Home Page]: .. [Course Outline]: course_outline.pdf [All Weeks]: indexcgi.cgi [Plain Text]: week10notes.txt [Week 10 Notes HTML]: week10notes.html [Shell Scripts]: 700_shell_scripts.html [Command Substitution]: 710_command_substitution.html [Integer Arithmetic]: 715_shell_arithmetic.html [Command Exit Status]: 720_exit_status.html [Shell Script Debugging]: 725_debugging_shell_scripts.html [Shell Control Structures]: 730_control_statements.html [List of Commands]: 900_unix_command_list.html [Video Tutorials on Lynda.com]: 910_lynda_index.html [Linux and Sysadmin News in the World]: 950_linux_world.html [Worksheet #08 HTML]: worksheet08.html [Assignment #09 HTML]: assignment09.html [Assignment #11 HTML]: assignment11.html [The VI (VIM) Text Editor]: 300_vi_text_editor.html [Assignment #04 HTML]: assignment04.html [Course Introduction: Install Libre Office]: 050_course_introduction.html#install-libreoffice-or-openoffice-into-windows [Worksheet #06 HTML]: worksheet06.html [Worksheet #08 ODT]: worksheet08.odt [Worksheet #08 PDF]: worksheet08.pdf [Practice Tests and Answers]: 000_practice_tests.html [Bring your favourite marker to your test]: data/sniff_markers.jpg "Bring your favourite marker to your test" [Quizzes and Tests]: 000_quizzes_and_tests.html [Brightspace CST8207]: https://brightspace.algonquincollege.com/d2l/home/117776 [Test Instructions]: 000_test_instructions.html [Assignment #12]: assignment12.html [Assignment #05 HTML]: assignment05.html [Create your own web page!]: 000_student_web_site.html [all the Winter 17W class images]: http://cst8207.idallen.ca/montage17w.cgi [all the Fall 17F class images]: http://cst8207.idallen.ca/montage17f.cgi [all the Winter 18W class images]: http://cst8207.idallen.ca/montage18w.cgi [all the Fall 18F class images]: http://cst8207.idallen.ca/montage18f.cgi [all the Winter 19W class images]: http://cst8207.idallen.ca/montage19w.cgi [Who is using the VIM editor?]: http://cst8207.idallen.ca/vim19w.cgi [Course Introduction]: 050_course_introduction.html [Week 03 Notes HTML]: week03notes.html [follow the directions]: 070_course_linux_server.html#getting-locked-out-of-the-server [Take Notes in Class]: data/remember.jpg "Take Notes in Class" [Pandoc Markdown]: http://johnmacfarlane.net/pandoc/