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Tutorial5: Redirection

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{{Admon/caution|DO NOT USE THIS VERSION OF THE LAB. This page will no longer be updated.|'''New version here:''' https://seneca-ictoer.github.io/ULI101/A-Tutorials/tutorial5 '''Andrew's students please go here:''' http://wiki.littlesvr.ca/wiki/OPS145_Lab_5}}

=REDIRECTION: STANDARD INPUT / STANDARD OUTPUT / STANDARD ERROR=

===Main Objectives of this Practice Tutorial===

:* xUnderstand and use the '''cut''', '''tr''', and '''wc''' Linux commands

:* xDefine the terms '''Standard Input''' (''stdin''), '''Standard Output''' (''stdout''), and '''Standard Error''' (''stderr'')

:* xUnderstand and use the '''>''', '''>>''', '''2>''', '''2>>''' symbols with Linux commands

:* xUnderstand the purpose of the the '''/dev/null''' file and the '''Here Document'''

:* xDefine the term '''pipeline command''' and explain how a pipeline command functions

:* xDefine the term '''filter''' and how it relates to pipeline commands

:* xUse the '''semicolon''' ";" and '''grouping''' "( )" symbols to issue multiple Unix / Linux commands on a single line :* Use the '''backslash''' "\" symbol to spread-out long Unix/Linux commands over multiple lines

===Tutorial Reference Material===

|colspan="2" style="font-size:16px;font-weight:bold;border-bottom: thin solid black;border-spacing:0px;"|Course Notes

|colspan="2" style="font-size:16px;font-weight:bold;border-bottom: thin solid black;border-spacing:0px;padding-left:15px;"|Linux Command/Shortcut Reference

|colspan="1" style="font-size:16px;font-weight:bold;border-bottom: thin solid black;border-spacing:0px;padding-left:15px;"|YouTube Videos

|- valign="top" style="padding-left:15px;"

|colspan="2" |~~Course Notes~~'''Slides:'''<ul><li>Week 5 Lecture 1 Notes: [https://~~ict~~wiki.cdot.senecacollege.ca/~~~murray~~uli101/slides/ULI101-5.~~saul~~1.pdf PDF] | https://wiki.cdot.senecacollege.ca/uli101/slides/ULI101-~~Week5~~5.1.pptx PPTX]</li><li>Week 5 Lecture 2 Notes: [https://wiki.cdot.senecacollege.ca/uli101/slides/ULI101-5.2.pdf PDF] | [https://~~ict~~wiki.cdot.senecacollege.ca/~~~murray.saul~~uli101/~~uli101~~slides/ULI101-~~Week5~~5.2.pptx PPTX] </li></ul> | style="padding-left:15px;" |'''Redirection:'''* [http://www.linfo.org/standard_input.html Standard Input (stdin)]* [http://www.linfo.org/standard_output.html Standard Output (stdout)]* [http://www.linfo.org/standard_error.html Standard Error (stderr)]* [http://www.linfo.org/pipe.html Pipeline Commands] '''Multiple Commands:'''* [https://www.javatpoint.com/linux-semicolon Semicolon] * [https://www.gnu.org/software/bash/manual/html_node/Command-Grouping.html Grouping ( )] | style="padding-left:15px;"|'''Redirection Filters:'''* [http://man7.org/linux/man-pages/man1/more.1.html more] , [http://man7.org/linux/man-pages/man1/less.1.html less] * [http://man7.org/linux/man-pages/man1/head.1.html head] , [http://man7.org/linux/man-pages/man1/tail.1.html tail]* [http://man7.org/linux/man-pages/man1/sort.1.html sort] * [http://man7.org/linux/man-pages/man1/uniq.1.html uniq] * [http://linuxcommand.org/lc3_man_pages/grep1.html grep] * [http://man7.org/linux/man-pages/man1/cut.1.html cut] * [http://linuxcommand.org/lc3_man_pages/tr1.html tr] * [http://man7.org/linux/man-pages/man1/wc.1.html wc] * [http://man7.org/linux/man-pages/man1/tee.1.html tee] |colspan="1" style="padding-left:15px;" width="30%"|'''Brauer Instructional Videos:'''<ul><li>[https://www.youtube.com/watch?v=ocU34PcYn2U&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=4 Reading/Writing to Files (echo, stdin, stdout, stderr, >, >>, 2>, cat, more, less, man, date, diff, diff -y, find, wc]) </li></ul>|} = KEY CONCEPTS = ===Additional File Manipulation Commands=== Before proceeding, let's look at some additional commands used to manipulate content of text files. Refer to the table below regarding these text file manipulation commands: [[Image:manipulation-commands.png|left|700px|]] ===Redirection (Standard Input, Standard Output, Standard Error)=== '''Redirection''' can be defined as changing the way from where commands read input to where commands sends output. You can redirect input and output of a command. Reference: https://www.javatpoint.com/linux-input-output-redirection [[Image:stdin-symbol.png|thumb|right|250px|The '''standard input''' ('''stdin''') symbol that describes where a Unix/Linux command receives '''input''']]'''Standard input''' ('''stdin''') is a term which describes from where a command receives '''input'''. This would apply only to Unix/Linux commands that accept stdin input (like ''cat'', ''more'', ''less'', ''sort'', ''grep'', ''head'', ''tail'', ''tr'', ''cut'', ''wc'', etc.). ''Examples:'' tr 'a-z' 'A-Z' < words.txt cat < abc.txt sort < xyz.txt <table align="right"><tr><td>[[Image:stdout-symbol-1.png|thumb|right|250px|The '''standard out''' ('''stdout''') symbol with one greater than sign '''overwrites''' existing file content with command output]]</td><td>[[Image:stdout-symbol-2.png|thumb|right|250px|The '''standard output''' ('''stdout''') symbol with two greater than signs '''add''' command's output to '''bottom''' of existing file's contents.]]</td></tr></table>'''Standard output''' ('''stdout''') describes where a command sends its '''output'''. In the examples below, output from a command is sent to the '''monitor''', unless it is sent to a '''text file'''. ''Examples:'' ls -l ls -l > detailed-listing.txt ls /bin >> output.txt <table align="right"><tr><td>[[Image:stderr-symbol-1.png|thumb|right|250px|The '''standard error''' ('''sterr''') symbol with one greater than sign '''overwrites''' existing file content with command's '''error message'''.]]</td><td>[[Image:stderr-symbol-2.png|thumb|right|250px|The '''standard error''' ('''stderr''') symbol with two greater than signs '''add''' command's error message to '''bottom''' of existing file's contents.]]</td></tr></table>'''Standard Error''' ('''stderr''') describes where a command sends it's error messages. In the examples below we issue the pwd in capitals on purpose to generate an error message, which can be redirected to a '''text file'''. ''Examples:'' PWD PWD 2> error-message.txt PWD 2 >> error-messages.txt PWD 2> /dev/null ====The /dev/null File==== The '''/dev/null''' file (sometimes called the '''bit bucket''' or '''black hole''') is a special system file that '''discard''' all data written into it. This is useful to discard unwanted command output. ''Examples:'' LS 2> /dev/null ls > /dev/null find / -name "tempfile" 2> /dev/null ====The Here Document==== [[Image:Here Document.png|thumb|right|175px|The '''Here Document''' allows a user to redirect stdin from within the command itself.]]In Linux, the '''Here Document''' allows a user to redirect stdin from within the command itself.

''Example:''

| cat <<+ Line 1 Line 2 Line 3 + ~~Multiple Commands~~* Semicolon * Grouping ( )

===Pipeline Commands===

[[Image:pipe-diagram-1.png| ~~style="padding-left:15px;"~~thumb|right|450px|~~Redirection Filters~~A '''pipeline command''' sends a command's '''standard output''' directly to '''standard input''' of other command(s) without having to create temporary files.]]* head* tail* sort* grep* cut* tr* wc'''Pipeline Command:''' Having commands send their '''standard output''' <bru>directly<br/u>to '''standard input''' of other commands WITHOUT having to use '''temporary''' files.

Pipes that are used in a '''pipeline command''' are represented by the '''pipe''' "|" symbol.

A few simple commands can be '''combined''' to form a more powerful command line.

|colspan="1" style="padding-left:15px;" width="30%"|Brauer Instructional Videos:<ul><li>[https://www.youtube.com/watch?v=ocU34PcYn2U&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=4 Reading/Writing to Files (echo, stdin, stdout, stderr, >, >>, 2>, cat, more, less, man, date, diff, diff -y, find, wc]) </li></ul>

|}Commands to the '''right''' of the pipe symbol are referred to as '''filters'''. They are referred to as ''filters'' since those commands are used to '''modify''' the stdout of the previous command. Many commands can be "piped" together, but these commands (filters) must be chained in a specific order, depending on what you wish to accomplish

~~= KEY CONCEPTS =~~

''Examples:''

===~~Redirection~~=The tee Command====

x

[[Image:tee-diagram-1.png|thumb|right|250px|The '''tee''' utility can be used to '''split''' the flow of information. For example to save in a file as well as display on a screen. (Image licensed under [https://creativecommons.org/licenses/by-sa/3.0/ cc])]]

The '''tee''' utility can be used to split the flow of '''standard output''' between a '''text file''' and the '''terminal screen'''.

The '''tee''' option '''-a''' can be used to add content to the '''bottom''' of an existing file as opposed to ''overwriting'' the file's previous contents.

~~===Piping (Using Pipes)===~~The reason for the name "'''tee'''" is that the splitting of the flow of information resembles a capital T.

x

''Examples:''

===Multiple Commands Using Semicolon ~~; /~~ , Grouping ~~Commands ( )~~, and Backquotes===

xBesides piping, there are other ways that multiple commands may be placed in one line: commands may be separated by '''semi-colons'''. ''Example:'' sleep 5; ls Multiple commands can also be '''grouped''' by using parentheses. ''Example:'' (echo "Who is on:"; w) > whoson ('''''Note:''' all command output is sent to a file'') Commands may also be '''spread-out over multiple lines''', making it easier (for humans) to interpret a long command. The '''\''' symbol “''quotes-out''” the meaning of the '''ENTER''' key as text (i.e. ''new-line'' as instead of ''running'' the command).

~~In the next investigation... ~~''Example:''

echo "This will be split over multiple \ lines. Note that the shell will realize \ that a pipe requires another command, so \ it will automatically go to the next line" |tr '[a-z]' '[A-Z]'

~~ In this section, you will learn how to ...~~=INVESTIGATION 1: BASICS OF REDIRECTION=

'''ATTENTION''': This online tutorial will be required to be completed by '''Friday in week 6 by midnight''' to obtain a grade of '''2%''' towards this course

In this investigation, you will learn how to redirect '''standard input''', '''standard output''' and '''standard error''' when issuing Unix / Linux commands.

'''Perform the Following Steps:'''

# x'''Login''' to your matrix account and issue a command to '''confirm''' you are located in your '''home''' directory. # Issue the following Linux command to create the following directory: mkdir ~/redirect # Change to the '''~/redirect''' directory and confirm that you changed to that directory. # Use a text editor to create a file in your current directory called '''data.txt''' and enter the following text displayed below: This is line 1 This is line 2 This is line 3 # '''Save''' editing changes and '''exit''' the text editor. # Issue the following Linux command: tr 'a-z' 'A-Z' < data.txt What does this command do? # Issue the following Linux command: tr 'a-z' 'A-Z' < data.txt > output.txt What does this command do? What are the contents of the file ''output.txt''? # Issue the following Linux command: tr 'a-z' 'A-Z' > output.txt < data.txt What does this command do? Is there any difference in terms of this command and the previous command issued? # Issue the following Linux command: tr 'a-z' 'A-Z' >> output.txt < data.txt What happens to the content of the '''output.txt''' file? Why? # Issue the following Linux command: tail -2 < data.txt > output.txt What does this command do? Check the contents of the '''output.txt''' file to confirm. # Issue the following Linux command: tail -2 > output2.txt < data.txt Why does this command render the same results as the previous command? Try explaining how the command works in terms of '''stdin''' and then '''stdout'''. # Issue the following Linux command to create a file: cat > output3.txt # Enter the follow text displayed below: This is the file output3.txt # Press ctrl-d to exit the command. # Issue the '''cat''' command to view the contents of the file: '''output3.txt''' # Issue the following Linux command: cp ~jason.carman/uli101/cars . # Issue the '''cat''' command to view the contents of the '''cars''' file. # Issue the following Linux command: cut -c1-10 cars What did this command do? # Issue the following Linux command: cut -f5 cars > field5.txt What did this command do? Check the contents in the file '''field5.txt''' to see what happened. # Issue the following Linux command: cut -f1-3 cars > field123.txt What did this command do? (check file contents) # Issue the following Linux command: cut -f1,5 cars > field15.txt What did this command do? (check file contents) # Issue the following Linux command: wc cars > count.txt What information does the '''count.txt''' file contain? # Issue the following Linux command: wc -l cars > count1.txt What information does the '''count1.txt''' file contain? # Issue the following Linux command: wc -w cars > count2.txt What information does the '''count2.txt''' file contain? # Issue the following Linux command: ls -l > listing.txt What information does the '''listing.txt''' file contain? # Issue the following Linux command: pwd > listing.txt What happenned to the original contents of the file called '''listing.txt'''? Why? # Issue the following Linux command (use 2 greater-than signs): date >> listing.txt What information does the '''listing.txt''' file contain? Why? # Issue the following Linux command: cat listing.txt cars > combined.txt What information does the '''combined.txt''' file contain? Why? '''NOTE''': The '''cat''' command stands for "'''concatenate'''" which means to '''combine''' contents of multiple files into a single file. This is why the command is called "''cat''". # Issue the following Linux command: cat listing.txt cars murray 2> result.txt What is displayed on the monitor? What information does the '''result.txt''' file contain? Why? # Issue the following Linux command: cat listing.txt cars murray > myoutput.txt 2> /dev/null What is displayed on the monitor? What happened to the error message? # Issue the following Linux command: cat listing.txt cars murray > myoutput.txt 2> result.txt What is displayed on the monitor? what do those files contain? Why? The '''Here Document''' allows you to redirect stdin from with the Linux command itself. Let's get some practice using the Here Document. # Issue the following Linux command: cat <<+ line 1 line 2 line 3 + What do you notice? # Issue the following Linux command: grep 2 <<+ line 1 line 2 line 3 + What do you notice? How does this differ from the previous command? Why? # Issue the following Linux command: grep 2 > line2.txt <<+ line 1 line 2 line 3 + What do you notice? What is contained in the file '''line2.txt'''? Why? '''NOTE:''' You will now run a shell script to confirm that you properly issued Linux commands using redirection. # Issue the following Linux command to run a checking script: ~uli101/week5-check-1 # If you encounter errors, make corrections and '''re-run''' the checking script until you receive a congratulations message, then you can proceed. # Issue the '''ls''' command to see all of the '''temporary files''' that were created as a result of redirection. The problem with using these redirection symbols is that you create '''temporary text files''' that take up '''space''' on your file system. # Issue a Linux command (using '''Filename Expansion''') to '''remove''' those temporary text files in the current directory. # Issue the following Linux command to check that you removed ALL of those temporary text files: ~uli101/week5-check-2 # If you encounter errors, make corrections and '''re-run''' the checking script until you receive a congratulations message, then you can proceed.

:In the next investigation, you will ..be learning how to issue '''pipeline Linux commands''' which can accomplish tasks without creating temporary files.

=INVESTIGATION 2: REDIRECTION USING ~~PIPES~~ PIPELINE COMMANDS =

~~ ~~In this ~~section~~investigation, you will learn ~~how~~ to ..issue '''pipeline commands''' to to accomplish tasks without having to generate temporary files.

'''Perform the Following Steps:'''

# xConfirm that you are still located in the '''~/redirect''' directory. The '''problem''' with creating temporary files, is that they take up space on your server, and should be removed. You actually did that in the previous investigation. You will be issuing a '''pipeline command''' which will use the pipe symbol "|" that will send the stdout from a command as stdin into another command without having to create temporary files. # Issue the follow Linux '''pipeline command''': ls /bin | more What happened? Press '''q''' to exit display. # Issue the following Linux '''pipeline command''': ls /bin | who What happened? Although this pipeline command provides output, it '''does not work''' properly as a pipeline command since the '''who''' command is '''NOT''' designed to accept standard input.[[Image:pipe-diagram-1.png|thumb|right|350px|]] '''NOTE:''' When issuing pipeline commands, commands to the right of the pipe symbol must be designed to accept '''standard input'''. Since the ''who'' command does not, you did NOT see the contents of the '''/bin''' directory but only information relating to the ''who'' command. Therefore, the '''order''' of which you build your pipeline command and the '''type of command''' that is used as a ''filter'' is extremely important! # Issue the following Linux command: ls /bin/?? > listing.txt # Issue the following Linux command: sort listing.txt # Issue the following Linux command to remove the listing file: rm listing.txt # Issue the following Linux '''pipeline command''': ls /bin/?? | sort You should notice that the output from this pipeline command is the same output from the command you issued in '''step #5'''. # Issue the following Linux '''pipeline command''': ls /bin/?? | sort | more What is difference with this pipeline command as opposed to the previous pipeline command? Press '''q''' to exit display. # Issue the '''ls''' command. You should notice that '''no files have been created'''. Let's get practice issuing more pipeline commands using commands (previously learned or new) to be used as '''filters'''. # Issue the following Linux '''pipeline command''': ls /bin/?? | sort | head -5 What did you notice? # Issue the following Linux '''pipeline command''': ls /bin/???? | sort | grep r | tail -2 What did you notice? Could you predict the output prior to issuing this pipeline command? # Issue the following Linux '''pipeline command''': ls /bin/???? | sort | grep r | cut -c1-6 Try to explain step-by-step each process in the pipeline command (including ''filters'') to explain the final output from this pipeine command. # Confirm that you are still located in the '''~/redirect''' directory. # Issue the following Linux '''pipeline command''': ls /bin/???? | tee unsort.txt | sort | tee sort.txt | grep r | tee match.txt | head # Issue the '''ls''' command to view the contents of this redirectory. What did you notice? # View the contents of the '''text files''' that were created to see how the '''tee''' command was used in the previous pipeline command. What was the purpose of using the '''tee''' command for this pipeline command? You will now run a shell script to confirm that you properly issued that Linux pipeline command using the '''tee''' command and redirection. # Issue the following Linux command to run a checking script: ~uli101/week5-check-3 If you encounter errors, make corrections and '''re-run''' the checking script until you receive a congratulations message, then you can proceed. # Change to your '''home''' directory. # Remove the '''~/redirect''' directory and its contents. :In the next investigation, you will learn various techniques to issue '''multiple Linux commands''' on the same line, or issue a '''single Linux command over multiple lines'''.

=INVESTIGATION 3: ISSUING MULTIPLE UNIX/LINUX COMMANDS=

~~===Part 2: Performing Online Assignments ===~~In this investigation, you will learn how to issue multiple Unix / Linux commands in a single line or over multiple lines.

You are required to perform '''3 online assignments''' during this course. This online assignment is used to teach and reinforce Linux commands are techniques as well as using Linux commands to perform tasks and tests students on their knowledge of issuing Linux commands.

~~In this section, you will learn to~~ '''~~select~~ Perform the ~~correct section~~Following Steps:''' for your online assignments, how to perform the '''first two sections''' of assignment #1, how to '''verify''' that you successfully completed both sections, and how to '''exit''' your online assignment #1.

# Confirm you are located in your '''home''' directory in your Matrix account. # Issue the following Linux commands (using the ''semicolon'~~Perform the following steps:~~' character "''';'''~~[[Image:assign-initial-window.png|thumb|right|250px|Initial Assignment Window~~ " to ~~Allow Student to Select Correct Course Section. ]]# In your Matrix account, issue the following~~ separate each Linux command): ~~~uli101/assign1~~cal;pwd;date ~~# A screen similar to~~ Note the ~~one displayed on~~ output as well as the ~~right will appear.~~<bru>order<br/u>~~'''WARNING''': You need to select the CORRECT section for the course which you belong to~~of what each Linux command results.~~ If you do NOT select your correct section, your assignment may not be recorded for marks!~~ # ~~Select the '''letter(s)''' corresponding to~~ Issue the ~~correct '''ULI101 section''' and '''professor''' and press~~ following Linux commands: ~~ENTER~~(cal;pwd;date) ~~# After you have selected your course section, There will be a screen that provides several important notes before proceeding~~Was there any difference in the output of this command as opposed to the previous command? Let's see how grouping affects working with redirection. ~~Please take a few moments to read those notes and press~~ # Issue the following Linux commands: ~~ENTER~~cal;pwd;date > output.txt ~~to proceed. [[Image:assn-section-completion.png|thumb|right|250px|Main Assignment Window to View Which Sections Need to be Completed. ]]# The assignment main menu will then be displayed.~~ What happened? Where is the output for the '''~~NOTES:~~date'''command?<ulbr>~~<li>Near~~ Why isn't the ~~bottom of~~ output for the ~~window, you will see~~ '''~~"You are currently registered to"''' followed by the '''section letter~~cal''' and '''~~instructor name~~pwd'''~~. Double-check your course timetable to confirm~~ commands are NOT contained in that this the correct section letter. If you have selected the WRONG section, type C in the menu selection area and press ENTER. You will return back to the original window to select your correct course section.file? ~~</li><li>Near~~ # Issue a Linux command to view the ~~top~~ contents of the window displays the sections to complete in the assignment. You are NOT required to complete all sections at the same time. You can check the assignment #1 link on the ULI101 main WIKI page to note the due date for assignment #1. Sections that are NOT completed will be displayed in file called '''~~reverse text with a blue background~~output.txt'''~~. On the other hand, when you compete a section, then the section will appear as regular text~~ ~~(i.e not in reverse text).~~ What do you notice? ~~[[Image:assn-completed-window.png|thumb|right|250px|Main Assignment Window to Confirm Which Sections Have or Have Not Been Completed. ]]~~<~~/li~~br>~~<li>If you want to verify that you have completed sections for the assignment, look for the text~~ Let's use '''~~"Marks earned so far for ULI101 Assignment:"~~grouping''' and it will show how many sections have been completed. When it shows all sections completed, then your assignment is finished and you should receive full marks provided that you have selected your correct course section.to make modification to the previous command <br~~></li></ul~~># At Issue the ~~menu assignment #1 window, enter~~ following Linux commands: 1(cal;pwd;date) > output.txt in What did you notice? # Issue a Linux command to view the ~~menu selection area to begin~~ contents of the ~~first section~~ file called '''~~"Introduction to Unix Commands"~~output.txt'''. ~~# When you have completed this section, you will be returned to the main window.~~What does ''grouping'' do when issuing multiple Linux commands (separated by a semi-colon ";") that uses redirection? ~~View the contents of this window to confirm that you completed this section.~~ # Issue the following Linux pipeline command (using \ at the end of most lines): ~~# When you have time this week, enter~~ 2echo "This will be split over multiple \<~~/span~~br> in lines. Note that the ~~menu selection area to begin the first section called '''"Basic Unix Commands"'''.~~shell will realize \ that a pipe requires another command, so \ ~~# When you have completed this section, you~~ it will ~~be returned~~ automatically go to the ~~main window.~~next line" |tr '[a-z]' '[A-Z]'<br/span>~~View the contents of this window to confirm that you completed this section.~~ ~~'''NOTE:''' Although you are NOT allowed to use reference sheets for course evaluations, it~~ Did the command work? What is ~~recommended to create one for your personal use, and write down~~ the purpose of issuing a Linux ~~commands, their arguments and options, so your can successfully perform quizzes, midterm exam, and final exam.~~command in this way? # ~~Proceed to~~ Complete the ~~next section~~ Review Questions sections to ~~perform~~ get additional practice. Linux is about "doing"! The more practice questions you perform, the better mark you will achieve for this course and have a better foundation of issuing Linux commands to be more productive in your future courses.

= LINUX PRACTICE QUESTIONS =

simulate a quiz:

https://~~ict~~wiki.cdot.senecacollege.ca/~~~murray.saul~~uli101/~~uli101~~files/uli101_week5_practice.docx

Your instructor may take-up these questions during class. It is up to the student to attend classes in order to obtain the answers to the following questions. Your instructor will NOT provide these answers in any other form (eg. e-mail, etc).

When answering Linux command questions, refer to the following Inverted Tree Diagram. The linux directory is contained in your home directory. Assume that you just logged into your Matrix account. Directories are underlined.

[[Image:week5-dir.png|thumb|left|300px|]]

'''Review Questions:'''

# xWrite a single Linux command to provide a detailed listing of all files in the '''/etc''' directory, sending the output to a file called listing.txt in the “'''projects'''” directory (append output to existing file and use a relative pathname)# x Write a single Linux command to redirect the stderr from the command: '''cat a.txt b.txt c.txt''' to a file called '''error.txt''' contained in the “'''assignments'''” directory. (overwrite previous file’s contents and use only relative pathnames) # xWrite a single Linux command: '''cat ~/a.txt ~/b.txt ~/c.txt''' and redirect stdout to a file called “good.txt” to the “tests” directory and stderr to a file called “'''bad.txt'''” to the “'''tests'''” directory. (overwrite previous contents for both files and use only relative-to-home pathnames).# x~~# x# x# x# x~~Write a single Linux command to redirect the stdout from the command: '''cat a.txt b.txt c.txt''' to a file called wrong.txt contained in the “'''projects'''” directory and throw-out any standard error messages so they don’t appear on the screen (append output to existing file and use only relative pathnames). # ~~Create~~ Write a single Linux '''~~table~~pipeline command''' to display a detailed listing ~~each~~ of the '''projects''' directory but pause one screen at a time to view and navigate through all of the directory contents. Use a relative-to-home pathname.# Write a single Linux '''pipeline command~~, useful options that were mentioned~~ ''' to display the sorted contents (in reverse alphabetical order) of the ~~online assignment~~ “'''linux'''” directory. Use a relative pathname.#~~1 and~~ Assume that the text file called “'''.answers.txt'''” contains 10 lines. Write a single Linux pipeline command ~~purpose~~ to only displays lines 5 through 8 for this file. Use only relative pathnames.# Write a single Linux '''pipeline command''' to only display the contents of the “'''assignments'''” directory whose filenames match the ~~following~~ pattern “'''murray'''” (both upper or lowercase). Use an absolute pathname.# Write a single Linux ~~commands:~~ '''xpipeline command''' , to display the number of characters contained in the file called “'''x.answers.txt''' , ”. Use a relative-to-home pathname.# Write a single Linux '''xpipeline command''' , to display the number of lines contained in the file called “'''xquestions.txt''' , ”. Use a relative pathname.# Write a single Linux '''xpipeline command''' to display only the first 10 characters of each filename contained in your current directory. Also, there is will be a lot of output, so also pause at each screenful so you can navigate throughout the display contents. Use a relative pathname.# Create a '''xtable''' listing each Linux command, useful options that were mentioned in this tutorial for the following Linux commands: '''xcut''' , '''xtr''' , '''xwc''' , and '''xtee'''. _________________________________________________________________________________ Author: Murray Saul License: LGPL version 3Link: https://www.gnu.org/licenses/lgpl.html _________________________________________________________________________________

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