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=INTRODUCTION TO SHELL SCRIPTINGUSING SED & AWK UTILTIES=
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===Main Objectives of this Practice Tutorial===
:* Plan and create Use the '''sed''' command to '''manipulate text''' contained in a Shell Scriptfile.
:* Explain the purpose of List and explain several '''addresses''' and '''instructions''' associated with the '''she-bang linesed''' contained at the top of a shell scriptcommand.
:* Set Use the '''permissionssed''' and command as a '''executefilter''' a shell scriptwith Linux pipeline commands.
:* Use the '''environmentawk''' and command to '''user-definedmanipulate text''' variables contained in shell scriptsa file.
:* Use List and explain '''comparison operators''Command Substitution', '''variables''' and '''Math Operationsactions''' associated with the '''awk''' in shell scriptscommand.
:* Explain the purpose of the '''$?''' exit status and Use the '''testawk''' command. :* Use '''if''' and '''if-else''' logic statements in shell scripts. :* Use as a '''forfilter''' loop statement with a list in shell scriptsLinux pipeline commands.
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|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/shelltutorials/the-basics-of-using-the-sed-stream-editor-to-manipulate-text-in-linux Purpose of using the sed utility]* [https://www.digitalocean.com/community/tutorials/how-to-use-the-awk-language-to-manipulate-text-in-script linux Purposeof using the awk utility]
|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 Bash Shell Scripting - Part 114 Using the sed Utility]</li><li>[https://www.youtube.com/watch?v=cQepf9fY6cE Creating and Running a Shell ScriptOV3XzjDYgJo&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=13 Using the awk Utility]</li></ul>
|}
= KEY CONCEPTS =
''Examples:''<br><span style="color:blue;font-weight:bold;font-family:courier;">Syntax: sed [-n] 'address instruction''chmod u+x myscript.bash<br>./myscript.bash<br>/home/username/myscript.bash<br>~/myscript.bashfilename</span>'''<br><br>===Variables / Parameters===
'''Environment Variables''' [[Image:environment.png|thumb|right|500px|Examples of using '''Environment''' and '''User Defined''' variables.]]Shell '''environment variables''' shape the working environment whenever you are logged in Common shell. Some of these variables are displayed via Linux commands in the diagram displayed on the right-side.<br><br>You can issue the pipeline command <span style="font-family:courier;font-weight:bold">set | more</span><br>to view all variables.<br><br>Placing a dollar sign "<span style="font-family:courier;font-weight:bold">$</span>" prior to the variable name will cause the variable to expand to the value contained in the variable. '''User Defined Variables''' <b>User-defined variables</b> are variables that can be used in the shell script for '''customized''' purposes.<br><br>Data can be stored and removed within a variable using an '''equal sign'''.<br><br>The '''read''' command can be used to prompt the user to enter data into a variable.<br><br> '''Positional Parameters and Special Parameters''' [[Image:positional.png|thumb|right|220px|Examples of using '''positional''' and '''special''' parameters.]]A '''positional parameter''' is a variable within a shell program; its value is set from an argument specified on the command line that invokes the program.Positional parameters are numbered and their values are accessed by using<br>a preceding "'''$'''" (eg. '''$1''', '''$2''', '''$3''', etc.). The positional parameter '''$0''' refers to<br>either the '''name of shell''' where command was issued, or '''filename of shell script''' being executed.<br>If using '''positional parameters''' greater than '''9''', then you need to include number within braces.<br><br>ExamplesHow it Works: '''echo ${10}''', '''ls ${23}'''<br><br> The '''shift''' command can be used with positional parameters to shift positional parameters<br>to the left by one or more positions. There are a couple of ways to assign values as positional parameters::*Use the '''set''' command with the values as argument after the set command:*Run a shell script containing arguments There are a group of '''special parameters''' that can be used for shell scripting.<br>A few of these special parameters and their purpose are displayed below:<br>'''$*''' , '''“$*”''' , '''"$@"''' , '''$#''' , '''$?'''<br><br>
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'''Command SubstitutionAddress:''' [[Image:for-command-substitution.png|thumb|right|300px|Example of how a '''for loop with command substitution''' works.]]<i>'''Command substitution''' is a facility that allows a command<br>to be run and its output to be pasted back on the command line as arguments to another command.</i><br>Reference: https://en.wikipedia.org/wiki/Command_substitution<br><br>
* Can use a line number, to select a specific line (for example: '''5'''Usage)* Can specify a range of line numbers (for example:'''5,7''')* 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 '''/^[0-9].*[0-9]$/''') * If NO address is present, the instruction will apply to ALL lines
[[Image:sed.png|right|500px|]]''Examples'Instruction:''' <span style="font-family:courier;font-weight:bold">file $*'''Action''' to take for matched line(lss)<br>mail -s "message" $(cat email*Refer to table on right-side for list.txt) < message.txtof some<br>echo "The current directory is $(pwd)"<br>echo "The current hostname is $(hostname)"<br>echo "The date is: $(date +'%A %B %d, %Y')"<br>'common instructions''' and their purpose
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<pre span style="widthcolor:20%red;">if test condition then command(s) else command(s) fi'''ATTENTION''': 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</prespan><br><br>
'''Perform the Following Steps:'''
# '''Login''' to your matrix accountand confirm you are located in your '''home''' directory.<br><br># Issue a Linux command to create a directory called '''confirmsed''' you are located in your '''home''' directory.<br><br>We want # Issue a Linux command to create a Bash Shell script <u>change</u> to welcome the user by their ''username'sed''.<br>Let's first provide some useful tips directory and confirm that you are located in terms of selecting an appropriate name for the shell script'''sed''' directory.<br><br># Issue the following linux Linux command to check if your intended shell script namedownload the data.txt file<br>is already exists ('''copy and paste''' to be run automatically from the Bash shellsave time):<br><span style="color:blue;font-weight:bold;font-family:courier;">which hellowget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/data.txt</nowiki></span><br><br>You should notice that there is no output and therefore, this shell script name CAN be used# 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<br/span>[[Image:hello0sed-1.png|thumb|right|200px300px|Using a Issuing the '''text editorp''' to add Linux commands in to instruction without using the '''hello-n''' shell scriptoption (to suppress original output) will display lines twice.]]# Use a <br><br>The '''text editorp''' like instruction with the '''vised''' or command is used to<br>'''nanoprint''' to create the text file called (i.e. '''hello'display'') the contents of a text file.<br><br># Enter Issue the following two lines in your shell script, replacing "your-username" with your actual nameLinux command:<br><span style="color:blue;font-familyweight:courierbold;font-weightfamily:boldcourier;">echo<br>echo "Hello $USER"<br>echosed 'p' data.txt</span><br><br>'''NOTE:You should notice that each line appears twice''' .<br><br>The variable called reason why standard output appears twice is that the sed command<br>(without the '''USER-n option''' is ) displays all lines regardless of an address used.<br><br>We will use '''environment variablepipeline commands''' that contains to both display stdout to the screen and save to files<br>for <u>currentconfirmation</u> userof running these pipeline commands when run a '''checking-script'''s login namelater in this investigation. If you wanted to share your shell script with other users, when they run <br><br># Issue the shell script, they will greeted by following Linux pipeline command:<br><uspan style="color:blue;font-weight:bold;font-family:courier;">theirsed -n 'p' data.txt | tee sed-1.txt</uspan><br><br> usernameWhat do you notice? You should see only one line. <br><br>You can specify an ''Environment variables'address' make your shell script adaptable by ALL users.'' to display lines using the sed utility<br><br>(eg. ''line # '', '''Saveline #s''' your editing session and or range of '''exitline #s''' the text editor).<br><br>Instead of issuing # Issue the '''bash''' following Linux pipeline command followed by your shell script pathname as an ''argument'',:<br>let<span style="color:blue;font-weight:bold;font-family:courier;">sed -n 's simply run it by its filename1 p' data. This is the most common method of running shell scriptstxt | tee sed-2.txt</span><br><br>You should see the first line of the text file displayed.<table align="right"br>What other command is used to only display the first line in a file?<tr valign="top"br><tdbr>[[Image:nosed-execute2.png|thumb|right|230px500px|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 |An 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 '''error messages''' will appear when trying instruction is used to run '''substitute''' text<br>(a shell script by name that does NOT have 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 '2,5 s/TUTORIAL/LESSON/g' data.txt | tee sed-4.txt | more</span><br><br>What do you notice? View the original contents of lines 2 to 5 in the '''executedata.txt''' permissionsfile<br>in another shell to confirm that the substitution occurred.]]</tdbr><tdbr>[[Image:hello1sed-3.png|thumb|right|150px500px|Output from running your Using the sed command with the '''hello-q''' shell script (YourUserID representing <u>your</u> username)option to display up to a line number, then quit.]]The '''q''' instruction terminates or '''quits''' the execution of the sed utility as soon as it is read in a particular line or matching pattern.</tdbr></tablebr># Issue the following linux Linux pipeline command to run your shell script in your current directory:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed '11 q' data.txt | tee sed-5./hellotxt</span><br><br>What did you notice? How many lines were displayed<br>before the sed command exited?<br><br>You can use '''regular expressions''You should notice an error indicating you don't have permissions to run 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 filesame for using regular expressions as demonstrated in '''tutorial 9'''. You need to add <br>except the regular expression must be contained within '''execute permissionsforward slashes''' prior to running the shell script<br>(eg. <span style="font-family:courier;font-weight:bold;">/regexp/</span> ).<br><br># Issue [[Image:sed-4.png|thumb|right|400px|Using the following linux sed command to using regular expressions with '''addanchors''' execute permissions for your shell script.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x hellosed -n '/^The/ p' data.txt | tee sed-6.txt</span><br><br>What do you notice?<br><br># Re-run your shell scriptIssue the following Linux pipeline command: <br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/d$/ p' data./hellotxt | tee sed-7.txt</span><br><br>Did your shell script runWhat do you notice?<br><br><span style="color:red;">The '''ATTENTION:sed''' Students might get FRUSTRATED when performing their utility can also be used as a '''assignment 3filter''' when their Bash shell scripts have errorsto manipulate text that<br>was generated from Linux commands.<br><br>[[Image:sed-5. One major cause is png|thumb|right|400px|Using the the OUTPUT of their Bash shell script when run does not sed command with '''EXACTLY matchpipeline''' commands.]]# Issue the required output for the correct Bash shell scriptfollowing Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">who | sed -n '/^[a-m]/ p' | tee sed-8. This requires that txt | more</span><br><br>What did you CAREFULLY notice?<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | sed -n '/txt$/ p''read''' the requirements of your Bash shell script and create it to the EXACT specifications| tee sed-9.txt</span><br><br>What did you notice?<br><br># Issue the following Linux command to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">bash /home/murray.saul~uli101/myscripts/week10week11-check-1</span><br><br># If you encounter errors, make corrections and '''re-run''' the checking script until you<br>until you receive a congratulations message, then you can proceed.<br><br>::In the next investigation, you will learn to create and run shell scripts that<br >use '''variables''', '''positional''' and '''special parameters'''. You will also learn how to<br><u>add</u> a '''she-bang line''' at the top of a shell script to force it to run in a specified shell.<br><br>Proceed to the next investigation.<br><br>
=INVESTIGATION 2: USING THE AWK UTILITY =
In this investigation, you will learn how to use the awk utility to manipulate text and generate reports.
'''Perform the Following Steps:'''
# Confirm that Change to your '''home''' directory and issue a command to '''confirm'''<br>you are located in your '''home''' directory in your Matrix account.<br><br>Let's run shell scripts # Issue a Linux command to create a directory called '''awk'''<ubr>with</ubr> and # Issue a Linux command to <u>withoutchange</u> a to the '''she-bangawk''' line at directory and confirm you are located in the top of your shell script<br>to understand why a ''she-bang'awk''' line should be useddirectory.<br><br># Use Let's download a text editor to '''edit''' the '''hello''' shell script database file that you created in the <u>previous</u> investigationcontains information regarding classic cars.<br><br># Add Issue the following line to the <u>bottom</u> of the file (''linux command ('''copy''' and '''paste''' to prevent ''errors''save time):<br><span style="font-familycolor:courierblue;font-weight:bold;">echo "The current shell you are using isfont-family: $(ps -o cmd= -p $$|cut -d' ' -f1)courier;"</span><br>wget <brnowiki>'''FYIhttps:''' This command displays //ict.senecacollege.ca/~murray.saul/uli101/cars.txt</nowiki></span><br><br># Issue the '''namecat''' command to quickly view the contents of the ''shell'cars.txt' that the shell script is running in'' file.<br><br>The "'''print'''" action (command within ) is the <u>default<span style="font-family:courier;font-weight:bold;"/u>$( )action of awk to print</spanbr> uses all selected lines that match a technique known as '''command substitutionpattern'''.<br><br># Issue the following Linux command to change to the This '''action''' (contained in braces) can provide more options<br>such as printing '''Bourne Shellspecific fields''':of selected lines (or records) from a database.<br><span style="colorbr>[[Image:blue;fontawk-weight:bold;font-family:courier;">sh</span><br><br>You should notice your shell prompt changed that indicates that you are in a different shell1.png|thumb|right|400px|Using the awk command to display matches of the pattern '''ford'''.<br><br>[[Image:hello2]]# Issue the following linux command all to display all lines (i.e.png|thumb|right|275px|Changing records) in the Bourne shell and running shell script '''withoutcars.txt''' a '''She-bang'database that matches the pattern (or "make") called '' line.]]# Issue the following Linux command to run your shell script in the 'ford'Bourne Shell'':<br><span style="color:blue;font-weight:bold;font-family:courier;">.awk '/helloford/ {print}' cars.txt</span><br><br>You should see that you are currently running the shell script "We will use '''shpipeline commands'''"<br>which represents to both display stdout to the '''Bourne shell'''.screen and save to files for <bru>confirmation<br/u>of running these pipeline commands when run a '''NOTE:checking-script''' Due to the fact that shells (and their features) have '''evolved''' over a period of time,later in this investigation.<br>an error may occur if you include a <br># Issue the following linux pipeline command all to display records<br>in the '''NEWER shell featurecars.txt''' database that contain the pattern (i.e.g. ''Bash Shell''make) but run it in an '''OLDER shellford''' (For example: the ''Bourne Shell'').<<br><br>[[Imagespan style="color:sheblue;font-bangweight:bold;font-1.png|thumb|right|275px|Adding a family:courier;">awk '/ford/''shecars.txt | tee awk-bang line''' at the BEGINNING of the first line in you shell script forces the shell script to be run in that specific shell (in this case, the Bash shell).]]1.txt</span><br><br>What do you notice? You can add a '''special commentshould notice ALL lines displayed <u>without</u> using ''' called a search criteria'''she-bang line''' at the BEGINNING of the .<ubr>FIRST line</ubr> of your shell script to You can use ''builtin''force''' it to run in variables''' with the shell you want (for example: the Bash shell).<br><br> # Edit your '''helloprint''' shell script using a text editorcommand for further processing.<br><brWe 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 '''Insertfield number''' the following line at the .]]'''beginning$0''' of the - Current record (entire line)<br>'''first$1''' line of your hello file:- First field in record<br>'''$n''' - nth field in record<span style="fontbr>'''NR''' -family:courier;font-weight:bold;">#!/bin/bashRecord Number (order in database)</spanbr><br><br>This is referred to as a '''she-bang lineNF'''. It forces this script to be run - Number of fields in the '''Bash Shell'''.current record<br>When your Bash Shell script finishes execution<br>For a listing of more variables, you are returned to please consult your current shell that you are using (which in our case in Matrix, is still the Bash shell)course notes.<br><br>[[Image:hello3.png|thumb|right|275px|Changing # Issue the following linux pipeline command to display the Bourne shell and running shell script '''withmodel''' a , '''She-bangyear''' line (forcing script to run in the , '''Bashquantity''' shell).]]# and price<br>in the '''Savecars.txt''' your editing changes and database for makes of '''exitchevy''' your text editor.<br><br># While in the Bourne shell, issue the following Linux command:<br><span style="color:blue;font-weight:bold;font-family:courier;">.awk '/hello<chevy/span><br{print $2,$3,$4,$5}' cars.txt | tee awk-2.txt</span><br><br>You should notice Notice that the shell name is running in the a '''Bash shellspace'''.<is the delimiter for the fields that appear as standard output.<br><br> # It is a good idea to rename your shell script to include an The '''extensiontilde character''' to<br>explain that this is '''Bash Shell script~''' file (referred is used to as search for a "''portable Bash shell script''")pattern or display standard output for a particular field. <br><br># Issue the following Linux linux pipeline command to rename your shell script file:display all '''plymouths''' ('''plym''')<br>by '''model name''', '''price''' and '''quantity''':<br><span style="color:blue;font-weight:bold;font-family:courier;">mv hello hello.bash<awk '$1 ~ /plym/span>{print $2,$3,$4,$5}' cars.txt | tee awk-3.txt<br/span><br># Confirm that the modification work by running your Bash shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;"You can also use '''comparison operators''' to specify conditions for processing with matched patterns<br>when using the awk command./hello.bashSince they are used WITHIN the awk expression,</spanbr>they are not confused with redirection symbols<br><br># Enter [[Image:awk-3.png|thumb|right|400px|Using the following Linux awk command to display results based on '''exitcomparison operators''' the .]]''Bourne shell'<' and return to your ''Bash shell'': Less than<br>'''<span style="color:blue''' font-weight:bold font-family:courier;">exit</span><br><Less than or equal<br>Let's use some '''ENVIRONMENT variables>''' in our Bash Shell script. Greater than<br><br'''>=''' Greater than or equal<br>'''==''' Equal<br># Use a text editor to edit the shell script called '''hello.bash!=''' Not equal<br><br># Add Issue the following lines linux pipeline command to display display the <u>bottom</u> of the ''hello.bash'car make''', '''model''', '''quantity''' and '''price''' of all vehicles whose '''prices are less than $5,000''' file:<br><span style="font-family:courier<br><span style="color:blue;font-weight:bold;font-family:courier;">echo<br>echo "The current directory location is: awk '$PWD"5 <br>echo "The current user home directory is: 5000 {print $HOME"<br>echo1,$2,$4,$5}' cars.txt | tee awk-4.txt</span><br><br># Save your editing changes and exit your text editor.What do you notice?<br><br>[[Image:hello4-0.png|thumb|right|330px|Running # Issue the following linux pipeline command to display display '''price''',<u>modified</ubr> ''hello.bash'quantity''', '''model''' and '''car make''' of vehicles whose '''prices are less than $5,000''' Bash shell script by using relative pathname: <br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$5 < 5000 {print $5,$4,$2,$1}'cars./hellotxt | tee awk-5.bash''txt</span>]]# To confirm that you properly renamed your shell script,<br>run <br># Issue the following shell script:linux pipeline command to display the '''car make''',<br><span style'''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,$4}' cars./hellotxt | tee awk-6.bashtxt</span><br><br>Take time to view the output and the values of the environment variables[[Image:awk-4.<br><br># Issue png|thumb|right|400px|Using the following Linux awk command to add your current directory to the display combined search results based on '''PATHcompound operators''' environment variable:.]]Combined pattern searches can be made<br><span style="color:blue;font-weightby using '''compound operator''' symbols:bold;font-family:courier;">PATH=$PATH:.</spanbr><br>'''&&''' (and)<br>[[Image:hello4.png'''|thumb|right|330px|Running <u>modified</u> ''hello.bash'' Bash shell script by entering (or)<ubr>just</ubr> # Issue the following linux pipeline command to list all '''filenamefords''' (i.e. <span style="font-family:courier;">br>whose '''price is greater than $10,000'hello.bash'':</spanbr> and NOT <span style="color:blue;font-weight:bold;font-family:courier;">awk ''.$1 ~ /helloford/ && $5 > 10000 {print $0}' cars.bash''txt | tee awk-7.txt</span> shown in previous diagram).]]<br><br># Issue the following Linux linux command to confirm that the current directory ('''"."copy and paste''' has been added to the '''PATH''' environment variablesave time):<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $PATHwget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/cars2.txt</nowiki></span><br><br># Issue the following '''cat''' command to run your Bash shell script just by name:quickly view the contents of the '''cars2.txt''' file.<br><span style="color:blue;font-weight:bold;font-family:courier;">hello.bash</span>br># Issue the following linux pipeline command to display the '''year'''<br><br>Did your Bash shell script run?<br><br># Exit your Matrix session, and log back into your Matrix session.<br><br># Re-run the '''hello.bashquantity''' shell script by just using the name.<br><br>What did you notice?<br><br>The setting of the of cars that '''PATHbegin''' environment variable only worked in with the current session only.<br>If you exit '''letter 'f'''' for the current Matrix session, then the recently changed settings for environment variables will be lost'''cars2.txt''' database:<br>You will in a <u>future</u> tutorial how to set environment variables in '''start-up''' files.<br><br><span style=span style="color:redblue;">'''ATTENTIONfont-weight:bold;font-family:courier;">awk '$1 ~ /^f/ {print $2,$4}'' Students will get FRUSTRATED when performing their '''assignment 3''' when their Bash shell scripts have errorscars2. One major cause is the txt | tee awk-8.txt</span><br><br>What did you notice?<br><br>The problem is that the OUTPUT of their Bash shell script when run does not '''EXACTLY matchcars2.txt''' the required output for the correct Bash shell script. This requires that you CAREFULLY database separates each field by a semi-colon ('''read;''' the requirements of your Bash shell script and create it to the EXACT specifications) </spanu>.instead<br/u>of '''TAB'''.<br># Issue Therefore, it does not recognize the following Linux command to run a checking script:second and fourth fields.<br><span style="color:blue;fontbr>You need to issue awk with the -weight:bold;fontF option to indicate that this file's fields are separated (delimited) by a semi-family:courier;"colorn.<br>bash /home/murray.saul/myscripts/week10-check-2 | more</span><<br># Issue the following linux pipeline command to display the '''year'''<br>If you encounter errors, make corrections and and '''quantity''' of cars that '''re-runbegin''' with the checking script until you<br>receive a congratulations message, then you can proceed.<br><br>Let's create a Bash shell script that contain ''letter 'f'''' for the '''user-created variablescars2.txt'''.database:<br><br># Use a text editor to create a Bash shell script called '''userspan style="color:blue;font-weight:bold;font-variables.bash'''<brfamily:courier;"><br># Add the following lines to the beginning of the awk -F";" '$1 ~ /^f/ {print $2,$4}'usercars2.txt | tee awk-variables9.bash'' file:<br>txt</span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>read -p "Enter your Full Name: " name<br>read -p "Enter your age (in years): " ageWhat did you notice this time?<br>echo "Hello $name - You are $age years old"</spanbr># Issue the following to run a checking script:<br><br># Save your editing changes and exit your text editor.<br><br>[[Imagespan style="color:blue;font-weight:userbold;font-variable1.png|thumb|right|300px|Prompting user to enter data via the '''read family:courier;">~uli101/week11-p''' command storing into '''usercheck-created variable'''.]]# Issue the 2</span><br><br>If you encounter errors, make corrections and '''chmodre-run''' command to add '''execute permissions''' for the user for the '''user-variables.bash''' file.checking script until you<br><br># Issue the following to run the user-variables.bash Bash shell script<br> (enter your Full name and age when prompted):<br><span style="color:blue;font-weight:bold;font-family:courier;">./user-variables.bash</span><br><br>What did receive a congratulations message, then you notice?<br><br># Use a text editor to '''modify''' your Bash shell script called '''user-variables.bash'''<br><br># '''Insert''' the following lines immediately <u>'''below'''</u> the '''she-bang''' line:<br><span style="font-family:courier;font-weight:bold;">age=25<br>readonly age</span><br><br># Save your editing changes and exit your text editor.<br><br>[[Image:user-variable2.png|thumb|right|330px|Trying to change the value of a '''read-only''' variable'''.]]# Issue the following to run the user-variables.bash Bash shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">./user-variables.bash</span><br><br>What do you notice when you try to change the age variable? Why?<br><br>Let's use '''positional parameters''' and '''special parameters''' in a Bash shell script.<br><br># Use a text editor to create a file called '''parameters.bash'''<br><br># Add the following lines to the beginning of this file:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>echo \$0: $0<br>echo \$2: $2<br>echo \$3: $3<br><br>echo \$#: $#<br>echo \$*: $*<br><br>shift 2<br>echo \$#: $#<br>echo \$*: $*</span><br><br># Save your editing changes and exit your text editor.<br><br>Notice how the quoting character "'''\'''" is used to display positional parameters like "'''$2'''"<br>as opposed to the value stored in the <u>second</u> positional parameter.<br><br># Issue the '''chmod''' command to add '''execute permissions''' for the user for the '''parameters.bash''' file.<br><br>[[Image:parameter1.png|thumb|right|250px|Results from running shell script (with arguments) that use '''positional parameters''' and '''special parameters'''.]]# Issue the following to run the '''user-variables.bash''' Bash shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">./parameters.bash</span><br><br>What happened?<br><br>The values for some of the ''positional parameters'' and ''special parameters'' may NOT be<br>displayed properly since you did NOT provide any '''arguments''' when <u>running</u> your Bash shell script.<br><br># Issue the following to run the user-variables.bash Bash shell script with arguments:<br><span style="color:blue;font-weight:bold;font-family:courier;">can proceed./parameters.bash 1 2 3 4 5 6 7 8</span><br><br>What do you notice?<br><br>Take some time to view the results and how the ''parameters'' have changed when using the '''shift''' command. <br>
= LINUX PRACTICE QUESTIONS =
https://ict.senecacollege.ca/~murray.saul/uli101/uli101_week11_practice.docx
''For example'Review Questions:'''
Note the contents from the following tab-delimited file called '''~murray.saul/uli101/stuff.txt''':
(this file pathname exists for checking your work)
'''Perform Part B: Writing Linux Commands Using the Following Steps:sed Utility'''
'''Part C: Writing Linux Commands Using the awk Utility'''
Note the contents from the following tab-delimited file called '''~murray.saul/uli101/stuff.txt''':
(this file pathname exists for checking your work)
'''Part D: Writing Linux Commands Using the awk Utility'''
# Write a Linux awk command to display all records for the file: '''~/cars''' whose fifth field is greater than 10000.<br><br># Write a Linux awk command to display the first and fourth fields for the file:'''Walkthru ~/cars''' whose fifth field begins with a number.<br><br>#1Write a Linux awk command to display the second and third fields for the file:'''~/cars''' for records that match the pattern “chevy”.<br><br># Write a Linux awk command to display the first and second fields for all the records contained in the file: '''~/cars'''<br><br>
[[Category:ULI101]]