Changes

:* Define Understand and use the terms '''Standard Input''' (''cut'stdin'''), '''Standard Outputtr''' ('''stdout'''), and '''Standard Error''' ('''stderrwc''')Linux commands

:* Understand Define the purposes of redirection symbols terms '''>Standard Input''', (''stdin'>>'), '', 'Standard Output''2>'('', stdout''), and '2>>''Standard Error', ''('|'stderr'' and define their purpose in terms of redirection)

:* Understand and use the purpose of the additional file manipulation commands: '''cut>''', '''>>''', '''tr2>''', and '''wc2>>'''symbols with Linux commands

:* Define Understand the purpose of the the term '''pipeline command/dev/null''' file and explain how a pipeline command works in terms of redirectionthe '''Here Document'''

:* Define the term '''filterpipeline command''' and explain how it relates to redirection using a pipeline commandscommand functions

:* Understand how to use Define the term '''semicolonfilter''' symbol "''';'''" and how it relates to issue multiple Unix / Linux pipeline commands

:* Understand how to use Use the '''groupingsemicolon''' using the symbols ";" and '''grouping''' "( )" symbols to issue multiple Unix / Linux commands on a single line :* Use the '''backslash''' "\" and how it is used symbol to issue multiple spread-out long Unix / Linux commandsover multiple lines

|colspan="2" |Course Notes'''Slides:'''<ul><li>Week 5 Lecture 1 Notes:<br>[https://ictwiki.cdot.senecacollege.ca/~murrayuli101/slides/ULI101-5.1.pdf PDF] | https://wiki.cdot.senecacollege.ca/uli101/slides/ULI101-5.1.pptx PPTX]</li><li>Week 5 Lecture 2 Notes:<br> [https://wiki.cdot.senecacollege.saulca/uli101/slides/ULI101-Week55.2.pdf PDF] | [https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101slides/ULI101-Week55.2.pptx PPTX]<br></li></ul>

| style="padding-left:15px;" |'''Redirection:'''

* [http://www.linfo.org/pipe.html Piping (pipes)Pipeline Commands]<br><br>'''Multiple Commands:'''

| style="padding-left:15px;"|'''Redirection Filters:'''

|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<br>(echo, stdin, stdout, stderr, >, >>, 2>, cat, more, less, man, date, diff, diff -y, find, wc])<br></li></ul>

<i>''... 'Redirection''standard streams''' are preconnected can be defined as changing the way from where commands read input and to where commands sends output communication channels between a computer program and its environment when it begins execution. The three <br>You can redirect input/output (I/O) connections are called '''standard input''' ('''stdin'''), '''standard output''' ('''stdout''') and '''standard error''' ('''stderr'''). Originally I/O happened via a physically connected system console (input via keyboard, output via monitor), but standard streams '''abstract''' this. When of a command is executed via an interactive shell, the streams are typically connected to the text terminal on which the shell is running, but can be changed with '''redirection''' or a '''pipeline'''. ''</i>

Reference: https://enwww.wikipediajavatpoint.orgcom/wiki/Standard_streamslinux-input-output-redirection

'''Standard input''' ('''stdin''') is a term which describes from where a command receives '''input'''.<br>This would apply only to Unix/Linux commands that accept stdin input <br>(like ''cat'', ''more'', ''less'', ''sort'', ''grep'', ''head'', ''tail'', ''tr'', ''cut'', ''wc'', etc.).<br>With the examples below, standard input is being sent into the command from the text file.

<table align="right"><tr><td>[[Image:stdout-symbol-1.png|thumb|right|250px|The '''standard inputout''' ('''stdinstdout''') 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 inputoutput''' ('''stdinstdout''') 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 itits '''s output'''.<br>In the examples below, output from a command is sent to the '''monitor''', unless it is sent to a '''regular text file'''.<br>We will discuss another redirection technique called '''pipelines''' later. 

<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'''Examples (remember, Unix'''stderr''') symbol with two greater than signs '''add''' command's error message to '''bottom''' of existing file's contents.]]</td></tr></Linux is case sensitive and issuing PWD table>'''Standard Error''' ('''stderr''') describes where a command sends it's error messages. In the examples below we issue the pwd in caps will capitals on purpose to generate an error message), which can be redirected to a '''text file'''.  ''Examples:''

These commands are displayed in the table below<span style="font-family:courier;font-weight:bold;">LS 2> /dev/null<br>ls > /dev/null<br>find / -name "tempfile" 2> /dev/null</span><br><br>

<table cellpadding="5"><tr><th style="border-bottom: 1px solid black;text-align:left;">Linux Command</th><th style="border-bottom: 1px solid black;text-align:left;">Purpose</th></tr><tr valign="top"><td>'''cut'''</td><td>'''Used to extract fields and characters from records. The option '''-c''' option is used to cut by a character or a range of characters. The '''-f''' option indicates the field number or field range to display (this may require using the '''-d''' option to indicate the field separator (delimiter).'''<br><br>''Examples:''<br><span style="font-family:courier;font-weight:bold;">cut -f2 filename</span> - extract 2nd field from all records in file, using tab as delimiter (default)<br><span style="font-family:courier;font-weight:bold;">cut -d' ' -f2,5 filename</span> - extract 2nd and 5th field, using space as delimiter<br><span style="font-family:courier;font-weight:bold;">cut -d' ' -f1-3,5 filename</span> - extract 1st through 3rd and 5th fields, using space as delimiter<br><span style="font-family:courier;font-weight:bold;">cut -c3-5 filename</span> - extract 3rd to 5th characters</td></tr><tr valign="top"><td>'''tr'''</td><td>'''Used to translate characters to different characters.'''<br><br>''Examples:''<br><span style="font-family:courier;font-weight:bold;">tr a A < filename</span> - translate all characters "a" to "A"<br><span style="font-family:courier;font-weight:bold;">tr "[a-z]" "[A-Z]" < filename</span> - translate lowercase "a" through "z" to uppercase<br><span style="font-family:courier;font-weight:bold;">tr "a-z" "A-Z" < filename</span> - translate lowercase "a" through "z" to uppercase, different syntax (non-System V)<br><span style="font-family:courier;font-weight:bold;">tr ':' ' ' < filename</span> - translate all colons to spaces<br><span style="font-family:courier;font-weight:bold;">tr ' ' '\n' < filename</span> - translate all spaces to newline characters<br><span style="font-family:courier;font-weight:bold;">tr 'abc' 'A' < filename</span> - translate 'a', 'b', and 'c' to 'A', the last character in the "to" string repeats<br></td></tr><tr valign="top"><td><span styleHere Document="font-family:courier;font-weight:bold;">wc</span></td><td>'''Displays various counts of the contents of a file.'''<br><br>''Examples:''<br><span style="font-family:courier;font-weight:bold;">wc -l filename</span> - displays number of lines in file<br><span style="font-family:courier;font-weight:bold;">wc -c filename</span> - displays number of characters in file<br><span style="font-family:courier;font-weight:bold;">wc -w filename</span> - displays number of words in fil<br></td></tr></table>

[[Image:Here Document.png|thumb|right|175px|The '''/dev/nullHere Document''' file (sometimes called allows a user to redirect stdin from <u>within</u> the command itself.]]In Linux, the '''bit bucket''' or Here Document'''black hole''') is allows a special system file<br>that discards all data written into it. This is useful user to discard unwanted redirect stdin from within the command outputitself.

<span style="font-family:courier;font-weight:bold;">find / -name "tempfile" cat <<+<br>Line 1<br>Line 2<br> /dev/nullLine 3</spanbr>+<br><br>

===Piping (Using Pipes)Pipeline Commands===

'''Pipeline Command:''' Having commands send their s'''tandard standard output''' <u>directly</u> to '''standard input''' of other commands without WITHOUT having to use '''temporary ''' files. Pipes that are used in a '''pipeline command''' are represented by the '''pipe''' "|" symbol.<br>

A few simple commands can be '''combined ''' to form a more <u>powerful </u> command line.<br>

Pipes that 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 <u>previous command</u>. Many commands can be "piped" together, but these commands (filters) must be chained in a pipeline command are represented by the | symbol.specific order, depending on what you wish to accomplish

[[Image:tee-diagram-1.png|thumb|right|250px|The reason for the name "'''tee''' utility can be used to split " is that the flow splitting of information. For example to save in a file as well as display on a screen. <br>(Image licensed under [https://creativecommons.org/licenses/by-sa/3.0/ cc])]]The '''tee''' utility can be used to split the flow of information. The tee option '''-resembles a''' can be used to add content to the bottom of an existing file as opposed to overwriting the file's previous contentscapital T.

<span style="font-family:courier;font-weight:bold">sleep 5; ls</span> (''Note: each command will be executed when the previous command has terminated'')

<span style="font-family:courier;font-weight:bold">(echo "Who is on:"; w) > whoson</span><br>('''''Note:''' <u>all</u> command output is sent to a file'')

Commands may also be '''split spread-out over multiple lines''', making it easier (for humans) to interpret a long command.<br><br>You can add a The '''\'quote''symbol “' or 'quotes-out''"escape" ” the meaning of the newline character''' at the end of a line, to get rid of the special meaningENTER''' key as <u>text</u><br>(i.e. ''new-line'' as instead of newline (to end a ''running'' the command line).

<brspan style="color:red;">In this section, you '''ATTENTION''': This online tutorial will learn how be required to ...be completed by '''Friday in week 6 by midnight''' to obtain a grade of '''2%''' towards this course</span><br><br>

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

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

=INVESTIGATION 2: REDIRECTION USING PIPES PIPELINE COMMANDS =

In this sectioninvestigation, you will learn how to ..issue '''pipeline commands''' to to accomplish tasks <u>without</u> having to generate temporary files.

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

:In the next investigation, you will ..learn various techniques to issue '''multiple Linux commands'''<br>on the same line, or issue a '''single Linux command over multiple lines'''. =INVESTIGATION 3: MULTIPLE COMMANDS / COMMAND GROUPING =<br><br>

# xConfirm you are located in your '''home''' directory in your Matrix account.<br><br># Issue the following Linux commands (using the ''semicolon'' character "''';'''" to separate <u>each</u> Linux command):<br><span style="color:blue;font-weight:bold;font-family:courier;">cal;pwd;date</span><br><br>Note the output as well as the <u>order</u> of what each Linux command results.<br><br># Issue the following Linux commands: <span style="color:blue;font-weight:bold;font-family:courier;">(cal;pwd;date)</span><br><br>Was there any difference in the output of this command as opposed to the previous command?<br><br>Let's see how grouping affects working with redirection.<br><br># Issue the following Linux commands: <span style="color:blue;font-weight:bold;font-family:courier;">cal;pwd;date > output.txt</span><br><br>What happened? Where is the output for the '''date''' command?<br>Why isn't the output for the '''cal''' and '''pwd''' commands are NOT contained in that file?<br><br># Issue a Linux command to view the contents of the file called '''output.txt'''<br><br>What do you notice?<br><br>Let's use '''grouping''' to make modification to the previous command<br><br># Issue the following Linux commands: <span style="color:blue;font-weight:bold;font-family:courier;">(cal;pwd;date) > output.txt</span><br><br>What did you notice?<br><br># Issue a Linux command to view the contents of the file called '''output.txt'''<br><br>What does ''grouping'' do when issuing multiple Linux commands (separated by a semi-colon ";") that uses redirection?<br><br># Issue the following Linux pipeline command (using \ at the end of most lines):<br><span style="color:blue;font-family:courier;font-weight:bold">echo "This will be split over multiple \<br>lines. Note that the shell will realize \<br>that a pipe requires another command, so \<br>it will automatically go to the next line" |tr '[a-z]' '[A-Z]'</span><br><br>Did the command work? What is the purpose of issuing a Linux command in this way?<br><br># Complete the Review Questions sections to get additional practice.<br><br>

https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101files/uli101_week5_practice.docx

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

# Write a single Linux command to provide a detailed listing of all files in the '''/bin etc''' directory, sending the output to a file called listing.txt in the “projects” “'''projects'''” directory (append output to existing file and use a relative pathname)# Write a single Linux command to redirect the stderr from the command:<br>'''cat a.txt b.txt c.txt ''' to a file called '''error.txt ''' contained in the “assignments” “'''assignments'''” directory. (overwrite previous file’s contents and use only relative pathnames) # Write 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“'''bad.txt” txt'''” to the “tests” “'''tests'''” directory. (overwrite previous contents for both files and use only relative-to-home pathnames).# Write a single Linux command to redirect the stdout from the command:<br>'''cat a.txt b.txt c.txt ''' to a file called wrong.txt contained in the “projects” “'''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).<br><br># Write a single Linux '''pipeline command ''' to display a detailed listing of the “projects “directory '''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 ''' to display the sorted contents (in reverse alphabetical order) of the “linux” “'''linux'''” directory. Use a relative pathname.# Assume that the text file called “'''.answers.txt” txt'''” contains 10 lines. Write a single Linux pipeline command 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” “'''assignments'''” directory whose filenames match the pattern “murray” “'''murray'''” (both upper or lowercase). Use an absolute pathname.# Write a single Linux '''pipeline command ''' to display the number of characters contained in the file called “'''.answers.txt”txt'''”. Use a relative-to-home pathname.# Write a single Linux '''pipeline command ''' to display the number of lines contained in the file called “questions“'''questions.txt”txt'''”. Use a relative pathname.# Write a single Linux '''pipeline 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.