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Tutorial10: Shell Scripting - Part 1

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=INTRODUCTION TO SHELL SCRIPTINGUSING SED & AWK UTILTIES=
<br>
===Main Objectives of this Practice Tutorial===
:* Understand Use the process for planning prior '''sed''' command to writing '''manipulate text''' contained in a shell scriptfile.
:* Understand List and explain several '''addresses''' and '''instructions''' associated with the purpose of a she-bang line contained at the top of a shell script'''sed''' command.
:* Setting permissions for Use the '''sed''' command as a shell script and properly execute a shell script'''filter''' with Linux pipeline commands.
:* Understand and use environment and user-defined variables within Use the '''awk''' command to '''manipulate text''' contained in a shell scriptfile.
:* Understand List and explain '''comparison operators''', '''variables''' and '''actions''' associated with the purpose of control flow statements used with shell scripts'''awk''' command.
:* Use the test '''awk''' command to test various conditionsas a '''filter''' with Linux pipeline commands:* Use the if logic statement and the for loop statement within shell scripts.<br><br>
===Tutorial Reference Material===
|- valign="top" style="padding-left:15px;"
|colspan="2" |Course Notes'''Slides''':<ul><li>Week 11 Lecture 1 Notes:<br> [[Media:ULI101-Week11.1.pdf | PDF]] | [https://ictmatrix.senecacollege.ca/~murraychris.sauljohnson/uli101ULI101/ULI101-Week11.1.pptx PPTX]</li><li>Week 11 Lecture 2 Notes:<br> [[Media:ULI101-Week10Week11.2.pdf | PDF]] | [https://ictmatrix.senecacollege.ca/~murrayjason.saulcarman/uli101slides/ULI101-Week10Week11.2.pptx PPTX]<br></li></ul>
| style="padding-left:15px;" |Shell Scripting'''Text Manipulation:'''* [https://searchdatacenterwww.techtargetdigitalocean.com/definitioncommunity/tutorials/shellthe-basics-of-using-the-sed-stream-editor-script to-manipulate-text-in-linux Purposeof using the sed utility]* [https://www.youtubedigitalocean.com/watch?v=cQepf9fY6cE Creating and Running a Shell Script]<br>Variables* [https:community/tutorials/opensource.com/article/19/8/whathow-to-use-arethe-environmentawk-variables Environment]* [https://www.linuxtechi.com/variableslanguage-into-shellmanipulate-scripting/#:~:text=User%20Defined%20Variables%3A,like%20a%20real%20computer%20program. User Defined-in-linux Purpose of using the awk utility]
| style="padding-left:15px;"|Control Flow Statements'''Commands:'''* [https://en.wikipediaman7.org/wikilinux/Control_flow Purpose]* [https:man-pages/man1/www.computerhopesed.com/unix/test1p.htm test commandhtml sed]* [https://ryanstutorialsman7.netorg/bash-scripting-tutoriallinux/bash-ifman-statements.php#:~:text=If%20statements%20(and%2C%20closely%20related,conditions%20that%20we%20may%20set. if statement]* [https:pages/man1/wwwawk.cyberciti.biz/faq/bash-for-loop/#:~:text=A%20'for%20loop'%20is%20a,files%20using%20a%20for%20loop1p. for loophtml awk]
 |colspan="1" style="padding-left:15px;" width="30%"|'''Brauer Instructional Videos:'''<ul><li>[https://www.youtube.com/watch?v=kxEP-KUhOSgnpU6S61AIko&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=5 Introduction to Shell Scripting14 Using the sed Utility]</li><li>[https://www.youtube.com/watch?v=XVTwbINXnk4OV3XzjDYgJo&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=6 13 Using Variables and Control Flow Statements in Shell Scriptingthe awk Utility]</ul>
|}
= KEY CONCEPTS =
A shell script is a computer program designed to be run by the Unix shell, a command-line interpreter.<br> The various dialects of shell scripts are considered to be scripting languages.
Reference: https://en.wikipedia.org/wiki/Shell_script===Using the sed Utility===
===Creating & Executing Shell Scripts===
[[Image:ipso.png|thumb|right|500px|An IPSO Diagram (INPUT, PROCESSING, STORAGE, OUTPUT) can be used to map-out and then list the sequence of steps to assist when coding your shell script.]]It is recommended to '''plan''' out on a piece of paper the purpose of the shell script.<br>You can do this by creating a simple '''IPSO''' diagram (stands for '''INPUT''', '''PROCESSING''', '''STORAGE''', '''OUTPUTUsage:''').
First, list the INPUTS into the script (eg. prompting user for data, reading data from file, etc), then listing the expected OUTPUTS from the script. You can then list the steps to process the INPUT to provide the OUTPUT (including file storage).'''<span style="color:blue;font-weight:bold;font-family:courier;">Syntax: sed [-n] 'address instruction' filename</span>'''
Once you have planned your shell script by listing the sequence of steps in your script, you need to create a file (using a '''text editor''') that will contain your Linux commands.<br>'''NOTE:''' Avoid using filenames of already existing Linux Commands to avoid confusion. Using shell script filenames that include the file extension of the shell that the script will run within is recommended.
'''Using a Shebang LineHow it Works:'''
[[Image:shebang.png|thumb|right|200px|* The '''shebang line''' sed command reads all lines in the input file and will be exposed to the expression<ubr>must</u> appear on the '''first (i.e. area contained within quotes) one line''' at a time.* The expression can be within single quotes or double quotes.* The expression contains an address (match condition) and at the '''beginning''' of the shell scriptan instruction (operation).]]* If you are learning Bash scripting by reading other people’s code you might have noticed<br>that the first line in the scripts starts with the #! characters and the path to the Bash interpretermatches the address, then it will perform the instruction.This sequence of characters (#!) is called * Lines will display be default unless the '''shebang–n''' and option is used to tell the operating systemsuppress default display<br>which interpreter to use to parse the rest of the file. Reference'''Address: https://linuxize.com/post/bash-shebang/'''
The * Can use a line number, to select a specific line (for example: '''shebang line5''' <u>must</u> appear on the )* Can specify a range of line numbers (for example: '''first line5,7''' and at the )* Regular expressions are contained within forward slashes (e.g. /regular-expression/)* Can specify a regular expression to select all lines that match a pattern (e.g '''beginning/^[0-9].*[0-9]$/''' of ) * If NO address is present, the shell script,<br>otherwise, it instruction will be treated as a regular comment and ignored.apply to ALL lines
'''Setting Permissions &amp; Running a Shell Script'''
To run your shell script by name, you need [[Image:sed.png|right|500px|]]'''Instruction:'''*'''Action''' to take for matched line(s)*Refer to assign execute permissions table on right-side for the user.list of some<br>'''common instructions''' and their purpose<br><br>To run the shell script, you can execute it using a relative, absolute, or relative-to-home pathname
'''Example:<br><br><span style="font-family:courier;">chmod u+x myscript.bash<br>./myscript.bash<br>/home/username/myscript.bash<br>~/myscript.bash</span>==Using the awk Utility==='''
===Using Variables in Shell Scripts==='''Usage:'''
<span style="color:blue;font-weight:bold;font-family:courier;">awk [-F] '''Definition'''selection-criteria {action}’ file-name</span>
'''Variables''' are used to '''store information''' to be referenced and manipulated in a computer program.<br>They also provide a way of labeling data with a descriptive name, so our programs can be understood<br>more clearly by the reader and ourselves.<br>'''Reference:''' https://launchschool.com/books/ruby/read/variables
'''How It Works:'''
* The '''Environment Variablesawk''' command reads all lines in the input file and will be exposed to the expression (contained within quotes) for processing.*The '''expression''' (contained in quotes) represents '''selection criteria''', and '''action''' to execute contained within braces '''{}'''* if selection criteria is matched, then action (between braces) is executed.* The '''–F''' option can be used to specify the default '''field delimiter''' (separator) character<br>eg. '''awk –F”;”''' (would indicate a semi-colon delimited input file).<br>'''Selection Criteria'''
* You can use a regular expression, enclosed within slashes, as a pattern. For example: '''/pattern/'''* The ~ operator tests whether a field or variable matches a regular expression. For example: '''$1 ~ /^[[Image0-9]/'''* The '''!~''' operator tests for no match. For example:environment'''$2 !~ /line/'''* You can perform both numeric and string comparisons using relational operators ( '''>''' , '''>=''' , '''<''' , '''<=''' , '''==''' , '''!=''' ).png|thumb|right|500px|Examples * You can combine any of the patterns using the Boolean operators '''Environment||''' (OR) and '''User Defined&&''' variables(AND).]]Shell environment variables shape the working environment whenever you are logged * You can use built-in Common shell. Some of these variables are displayed via Linux commands in the diagram displayed on the right-sidevariables (like NR or "record number" representing line number) with comparison operators.<br>(you can issue the pipeline command For example: '''NR >=1 && NR <= 5'''set | more<br>''' to view all variablesAction (execution):'''
Placing a dollar sign * Action to be executed is contained within braces '''{}'''* The '''print''' command can be used to display text (fields).* You can use parameters which represent fields within records (lines) within the expression of the awk utility.* The parameter '''$0'''represents all of the fields contained in the record (line) prior .* The parameters '''$1''', '''$2''', '''$3''' … '''$9''' represent the first, second and third to the variable name will cause 9th fields contained within the variable to expand to record. * Parameters greater than nine requires the value contained of the parameter to be placed within braces (for example: '''${10}''','''${11}''','''${12}''', etc.)* You can use built-in the variable'''variables''' (such as '''NR''' or "record number" representing line number)<br>eg. '''{print NR,$0}''' (will print record number, then entire record).
=INVESTIGATION 1: USING THE SED UTILITY=
<span style="color:red;">'''User Defined VariablesATTENTION''': Effective '''May 9, 2022''' - this online tutorial will be required to be completed by '''Friday in week 11 by midnight'''<br>to obtain a grade of '''2%''' towards this course</span><br><br>
'''User-defined variables''' are variables which can be '''created by the user''' and exist in the session. This means that no one can access user-defined variables that have been set by another userIn this investigation,<br>and when you will learn how to manipulate text using the session is closed these variables expire.<br>'''Reference:sed''' https://mariadbutility.com/kb/en/user-defined-variables/
Data can be stored and removed within a variable using an equal sign.<br>The '''read''' command can be used to prompt the user to enter data into a variable.<br>Refer to the diagram on the right-side to see how user-defined variables are assigned data.
'''Positional Parameters and Special ParametersPerform the Following Steps:'''
# '''Login''' to your matrix account and confirm you are located in your '''home''' directory.<br><br># Issue a Linux command to create a directory called '''sed'''<br><br># Issue a Linux command to <u>change</u> to the '''sed''' directory and confirm that you are located in the '''sed''' directory.<br><br># Issue the following Linux command to download the data.txt file<br>('''copy and paste''' to save time):<br><span style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/data.txt</nowiki></span><br><br># Issue the '''more''' command to quickly view the contents of the '''data.txt''' file.<br>When finished, exit the more command by pressing the letter <span style="color:blue;font-weight:bold;font-family:courier;">q</span>[[Image:positionalsed-1.png|thumb|right|220px300px|Examples of using Issuing the '''positionalp''' and instruction without using the '''special-n''' parametersoption (to suppress original output) will display lines twice.]]A <br><br>The '''p''' instruction with the '''positional parametersed''' command is used to<br>'''print''' (i.e. ''display'') the contents of a variable within a shell programtext file.<br><br># Issue the following Linux command:<br><span style="color:blue;font-weight:bold;font-family:courier; its value ">sed 'p' data.txt</span><br><br>'''NOTE: You should notice that each line appears twice'''.<br><br>The reason why standard output appears twice is set from an argument specified on that the sed command line that invokes <br>(without the program'''-n option''') displays all lines regardless of an address used.Positional parameters are numbered <br><br>We will use '''pipeline commands''' to both display stdout to the screen and are referred save to with files<br>for <u>confirmation</u> of running these pipeline commands when run a preceding "'''$checking-script'''later in this investigation.<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family: courier;">sed -n 'p' data.txt | tee sed-1.txt</span><br><br>What do you notice? You should see only one line.<br><br>You can specify an '''address'''to display lines using the sed utility<br>(eg. '$1'line #'', '''$line #s''' or range of '''line #s''').<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '1 p' data.txt | tee sed-2.txt</span><br><br>You should see the first line of the text file displayed.<br>What other command is used to only display the first line in a file?<br><br>[[Image:sed-2.png|thumb|right|500px|Using the sed command to display a '''range'''of lines.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '2, 5 p' data.txt | tee sed-3.txt</span><br><br>What is displayed? How would you modify the sed command to display the line range 10 to 50?<br><br>The '''s''' instruction is used to '''$3substitute'''text<br>(a similar to method was demonstrated in the vi editor in tutorial 9).<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed '2, and so on5 s/TUTORIAL/LESSON/g' data.txt | tee sed-4. The positional parameter $0 refers txt | more</span><br><br>What do you notice? View the original contents of lines 2 to either 5 in the name of '''data.txt''' file<br>in another shell where to confirm that the substitution occurred.<br><br>[[Image:sed-3.png|thumb|right|500px|Using the sed command was issuedwith the '''-q''' option to display up to a line number, then quit.]]The '''q''' instruction terminates or name '''quits''' the execution of shell script being executedthe sed utility as soon as it is read in a particular line or matching pattern.<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed '11 q' data.txt | tee sed-5. If using txt</span><br><br>What did you notice? How many lines were displayed<br>before the sed command exited?<br><br>You can use '''positional parametersregular expressions''' greater than to select lines that match a pattern. In fact,<br>the sed command was one of the <u>first</u> Linux commands that used regular expression.<br><br>The rules remain the same for using regular expressions as demonstrated in '''tutorial 9''', then you need to include number <br>except the regular expression must be contained within braces'''forward slashes'''<br>(eg. <span style="font-family:courier;font-weight:bold;">/regexp/</span> ).<br>Examples<br>[[Image: sed-4.png|thumb|right|400px|Using the sed command using regular expressions with '''anchors''echo '.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/^The/ p' data.txt | tee sed-6.txt</span><br><br>What do you notice?<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/d${10}/ p' data.txt | tee sed-7.txt</span><br><br>What do you notice?<br><br>The '''sed''' utility can also be used as a '''filter''' to manipulate text that<br>was generated from Linux commands.<br><br>[[Image:sed-5.png|thumb|right|400px|Using the sed command with ''', pipeline'''commands.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">who | sed -n '/^[a-m]/ p' | tee sed-8.txt | more</span><br><br>What did you notice?<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | sed -n '/txt${23}/ p' | tee sed-9.txt</span><br><br>What did you notice?<br><br># Issue the following to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week11-check-1</span><br><br>If you encounter errors, make corrections and '''re-run'''the checking script<br>until you receive a congratulations message, then you can proceed.<br><br>
The :In the next investigation, you will learn how to manipulate text using the '''shiftawk''' command can be used with positional parameters to shift positional parametersutility.<br><br>to the left by one or more positions.
There are a few ways to assign values as positional parameters=INVESTIGATION 2::*Use the '''set''' command with the values as argument after the set command:*Run a shell script containing arguments USING THE AWK UTILITY =
In this investigation, you will learn how to use the awk utility to manipulate text and generate reports.
There are a group of '''special parameters''' that can be used for shell scripting.<br>A few of these special parameters and their purpose are displayed belowPerform the Following Steps:<br>'''$*''' , '''“$*”''' , '''"$@"''' , '''$#''' , '''$?'''
Refer # Change to your '''home''' directory and issue a command to '''confirm'''<br>you are located in your ''home'' directory.<br><br># Issue a Linux command to create a directory called '''awk'''<br><br># Issue a Linux command to <u>change</u> to the '''awk''' directory and confirm you are located in the '''awk''' directory.<br><br>Let's download a database file that contains information regarding classic cars.<br><br># Issue the following linux command ('''copy and paste''' to save time):<br><span style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/cars.txt</nowiki></span><br><br># Issue the '''cat''' command to quickly view the contents of the '''cars.txt''' file.<br><br>The "'''print'''" action (command) is the <u>default</u> action of awk to print<br>all selected lines that match a '''pattern'''.<br><br>This '''action''' (contained in braces) can provide more options<br>such as printing '''specific fields''' of selected lines (or records) from a database.<br><br>[[Image:awk-1.png|thumb|right|400px|Using the awk command to display matches of the pattern '''ford'''.]]# Issue the following linux command all to display all lines (i.e. records) in the '''cars.txt''' database that matches the pattern (or "make") called '''ford''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '/ford/ {print}' cars.txt</span><br><br>We will use '''pipeline commands''' to both display stdout to the screen and save to files for <u>confirmation</u> of running these pipeline commands when run a '''checking-script''' later in this investigation.<br><br># Issue the diagram following linux pipeline command all to display records<br>in the '''cars.txt''' database that contain the pattern (i.e. make) '''ford''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '/ford/' cars.txt | tee awk-1.txt</span><br><br>What do you notice? You should notice ALL lines displayed <u>without</u> using '''search criteria'''.<br><br>You can use ''builtin'' '''variables''' with the '''print''' command for further processing.<br>We will discuss the following variables in this tutorial:<br><br>[[Image:awk-2.png|thumb|right |400px|Using the awk command to print search results by '''field number'''.]]'''$0''' - Current record (entire line)<br>'''$1''' - First field in record<br>'''$n''' - nth field in record<br>'''NR''' - Record Number (order in database)<br> '''NF''' - Number of fields in current record<br><br>For a listing of more variables, please consult your course notes.<br><br># Issue the following linux pipeline command to display the '''model''', '''year''', '''quantity''' and price<br>in the '''cars.txt''' database for makes of '''chevy''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '/chevy/ {print $2,$3,$4,$5}' cars.txt | tee awk-2.txt</span><br><br>Notice that a '''space''' is the delimiter for the fields that appear as standard output.<br><br>The '''tilde character''' '''~''' is used to search for a pattern or display standard output for a particular field.<br><br># Issue the following linux pipeline command to display all '''plymouths''' ('''plym''')<br>by '''model name''', '''price''' and '''quantity''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$1 ~ /plym/ {print $2,$3,$4,$5}' cars.txt | tee awk-3.txt</span><br><br>You can also use '''comparison operators''' to specify conditions for examples processing with matched patterns<br>when using positional the awk command. Since they are used WITHIN the awk expression,<br>they are not confused with redirection symbols<br><br>[[Image:awk-3.png|thumb|right|400px|Using the awk command to display results based on '''comparison operators'''.]]'''<''' &nbsp;&nbsp;&nbsp;&nbsp;Less than<br>'''<=''' &nbsp;&nbsp;Less than or equal<br>'''>''' &nbsp;&nbsp;&nbsp;&nbsp;Greater than<br>'''>=''' &nbsp;&nbsp;Greater than or equal<br>'''==''' &nbsp;&nbsp;Equal<br>'''!=''' &nbsp;&nbsp;&nbsp;Not equal<br><br># Issue the following linux pipeline command to display display the '''car make''', '''model''', '''quantity''' and '''price''' of all vehicles whose '''prices are less than $5,000''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$5 < 5000 {print $1,$2,$4,$5}' cars.txt | tee awk-4.txt</span><br><br>What do you notice?<br><br># Issue the following linux pipeline command to display display '''price''',<br>'''quantity''', '''model''' and '''car make''' of vehicles whose '''prices are less than $5,000''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$5 < 5000 {print $5,$4,$2,$1}' cars.txt | tee awk-5.txt</span><br><br># Issue the following linux pipeline command to display the '''car make''',<br>'''year''' and '''quantity''' of cars that '''begin''' with the '''letter 'f'''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$1 ~ /^f/ {print $1,$2,$4}' cars.txt | tee awk-6.txt</span><br><br>[[Image:awk-4.png|thumb|right|400px|Using the awk command to display combined search results based on '''compound operators'''.]]Combined pattern searches can be made<br>by using '''compound operator''' symbols:<br><br>'''&&''' &nbsp;&nbsp;&nbsp;&nbsp;(and)<br>'''||''' &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(or)<br><br># Issue the following linux pipeline command to list all '''fords'''<br>whose '''price is greater than $10,000''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$1 ~ /ford/ && $5 > 10000 {print $0}' cars.txt | tee awk-7.txt</span><br><br># Issue the following linux command ('''copy and paste''' to save time):<br><span style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/cars2.txt</nowiki></span><br><br># Issue the '''cat''' command to quickly view the contents of the '''cars2.txt''' file.<br><br># Issue the following linux pipeline command to display the '''year'''<br>and special parameters'''quantity''' of cars that '''begin''' with the '''letter 'f'''' for the '''cars2.txt''' database:<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$1 ~ /^f/ {print $2,$4}' cars2.txt | tee awk-8.txt</span><br><br>What did you notice?<br><br>The problem is that the '''cars2.txt''' database separates each field by a semi-colon (''';''') <u>instead</u> of '''TAB'''.<br>Therefore, it does not recognize the second and fourth fields.<br><br>You need to issue awk with the -F option to indicate that this file's fields are separated (delimited) by a semi-colorn.<br><br># Issue the following linux pipeline command to display the '''year'''<br>and '''quantity''' of cars that '''begin''' with the '''letter 'f'''' for the '''cars2.txt''' database:<br><span style="color:blue;font-weight:bold;font-family:courier;">awk -F";" '$1 ~ /^f/ {print $2,$4}' cars2.txt | tee awk-9.txt</span><br><br>What did you notice this time?<br><br># Issue the following to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week11-check-2</span><br><br>If you encounter errors, make corrections and '''re-run''' the checking script until you<br>receive a congratulations message, then you can proceed.<br><br>
=LINUX PRACTICE QUESTIONS ==Using Control Flow Statements in Shell Scripts=== <table align="right"><tr valign="top"><td>[[Image:test-1.png|thumb|right|140px|Examples of simple comparisons using the test command.]]</td><td>[[Image:test-2.png|thumb|right|140px|Examples of using additional comparisons using the test command.]]</td></table>Control Flow Statement are used to make your shell scripts more flexible and can adapt to changing situations.
The special parameter purpose of this section is to obtain '''$?extra practice''' Is used to determine the exit status of the previously issued Linux command.The exit status will either display a zero (representing TRUE) or a non-zero number (representing FALSE). This can be used to determined if a Linux command was correctly or incorrectly executedhelp with '''quizzes''', your '''midterm''', and your '''final exam'''.
The '''test''' Linux command Here is used a link to test conditions to see if they are '''TRUE''' (i.e. value '''zero''') or '''FALSE''' (i.e. value '''non-zero''') so they can be used the MS Word Document of ALL of the questions displayed below but with control flow statements extra room to control answer on the sequence of document tosimulate a shell script.quiz:
You CANNOT use the '''>''' or '''<''' symbols when using the test command since these are redirection symbolshttps://ict. Instead, you need to use options when performing numerical comparisonssenecacollege.Refer to the table below for test options and their purposesca/~murray.saul/uli101/uli101_week11_practice.docx
There are <u>other</u> comparison options that can be used with Your instructor may take-up these questions during class. It is up to the student to attend classes in order to obtain the test command such as testing answers to see if a regular file or directory pathname exists, or if the regular file pathname is –nonfollowing questions. Your instructor will NOT provide these answers in any other form (eg. e-emptymail, etc).
Refer to diagrams to the right involving the test command.
'''Logic StatementsReview Questions:'''
A '''logic statementPart A: Display Results from Using the sed Utility''' is used to determine which Linux commands to be executed based<br>on the result of a condition (i.e. TRUE (zero value) or FALSE (non-zero value)).
<table align="right"><tr valign="top"><td>[[Image:logicNote the contents from the following tab-1.png|thumb|right|250px|Example of using the delimited file called '''if''' logic control-flow statement~murray.]]<saul/td><td>[[Image:loop-1uli101/stuff.png|thumb|right|250px|Example of using the txt''':(this file pathname exists for''' looping control-flow statement.]]</td></table>checking your work)
There are several logic statements, but we will just concentrate on <pre>Line one.This is the second line.This is the if statementthird.<pre style="width:20%">This is line four.Five.Line six followsif test conditionFollowed by 7 thenNow line 8 command(s) and line ninefiFinally, line 10
</pre>
Refer to the diagram relating to logic statements on the right side for an example.
'''Loop Statements'''Write the results of each of the following Linux commands for the above-mentioned file:
A '''loop statement''' is a series of steps or sequence of statements executed repeatedly zero or more times satisfying the given condition is satisfied.<br>Reference: https://www.chegg.com/homework-help/definitions/loop-statement-3
There are several loops# <span style="font-family:courier;font-weight:bold">sed -n '3, but we will look at 6 p' ~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed '4 q' ~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed '/the for loop using a list/ d' ~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed 's/line/NUMBER/g' ~murray.saul/uli101/stuff.txt</span>
<pre style="width:20%">
for item in list
do
command(s)
done
</pre>
Refer to '''Part B: Writing Linux Commands Using the diagram relating to looping statements on the right side for an example.sed Utility'''
=INVESTIGATION 1: CREATING A SHELL SCRIPT=Write a single Linux command to perform the specified tasks for each of the following questions.
<br>
In this section, you will learn how to ...
# Write a Linux sed command to display only lines 5 to 9 for the file: '''~murray.saul/uli101/stuff.txt'''<br><br>
# Write a Linux sed command to display only lines the begin the pattern “and” for the file: '''~murray.saul/uli101/stuff.txt'''<br><br>
# Write a Linux sed command to display only lines that end with a digit for the file: '''~murray.saul/uli101/stuff.txt'''<br><br>
# Write a Linux sed command to save lines that match the pattern “line” (upper or lowercase) for the file: '''~murray.saul/uli101/stuff.txt''' and save results (overwriting previous contents) to: '''~/results.txt'''<br><br>
'''Part C: Writing Linux Commands Using the awk Utility'''
Note the contents from the following tab-delimited file called '''Perform the Following Steps:~murray.saul/uli101/stuff.txt''':(this file pathname exists for checking your work)
# x<brpre>Line one.This is the second line.This is the third.This is line four.Five.Line six followsFollowed by 7Now line 8and line nineFinally, line 10<br/pre>
In the next investigation, you will ...<br><br>
=INVESTIGATION 2'''Write the results of each of the following Linux commands for the above-mentioned file: USING VARIABLES IN SHELL SCRIPTS ='''
In this section, you will learn how to ...
# <span style="font-family:courier;font-weight:bold">awk ‘NR == 3 {print}’ ~murray.saul/uli101/stuff.txt</span><br><br>
# <span style="font-family:courier;font-weight:bold">awk ‘NR >= 2 && NR <= 5 {print}’ ~murray.saul/uli101/stuff.txt</span><br><br>
# <span style="font-family:courier;font-weight:bold">awk ‘$1 ~ /This/ {print $2}’ ~murray.saul/uli101/stuff.txt</span><br><br>
# <span style="font-family:courier;font-weight:bold">awk ‘$1 ~ /This/ {print $3,$2}’ ~murray.saul/uli101/stuff.txt</span><br><br>
'''Perform the Following Steps:''' # x<br><br> In the next investigation, you will ... =INVESTIGATION 3Part D: USING CONTROL FLOW STATEMENTS IN SHELL SCRIPTS = In this section, you will learn how to ...   '''Perform Writing Linux Commands Using the Following Steps:awk Utility'''
# x<br>
= LINUX PRACTICE QUESTIONS =Write a single Linux command to perform the specified tasks for each of the following questions.
The purpose of this section is to obtain '''extra practice''' to help with '''quizzes''', your '''midterm''', and your '''final exam'''.
Here # Write a Linux awk command to display all records for the file: '''~/cars''' whose fifth field is greater than 10000.<br><br># Write a link Linux awk command to display the MS Word Document of ALL of first and fourth fields for the questions displayed below but file: '''~/cars''' whose fifth field begins with extra room a number.<br><br># Write a Linux awk command to answer on display the document tosecond and third fields for the file: '''~/cars''' for records that match the pattern “chevy”.<br><br>simulate # Write a quizLinux awk command to display the first and second fields for all the records contained in the file:'''~/cars'''<br><br>
https://ict.senecacollege.ca/~murray.saul/uli101/uli101_week10_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).
 
 
'''Review Questions:'''
# Write a Bash shell script that clears the screen and displays the text Hello World on the screen.<br><br><br><br><br>What permissions are required to run this Bash shell script?<br><br><br>What are the different ways that you can run this Bash shell script from the command line?<br><br><br>
# Write a Bash shell script that clears the screen, prompts the user for their '''full name''' and then prompts the user for their '''age''', then clears the screen again and welcomes the user by their name and tells them their age.<br> <br><br><br><br><br><br><br>What comments would you add to the above script’s contents to properly document this Bash shell script to be understood for those users that would read / edit this Bash shell script’s contents?<br> <br><br>
# x
# x
# x
# x
# x
# x
[[Category:ULI101]]
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