=INTRODUCTION TO SHELL SCRIPTINGUSING SED & AWK UTILTIES=

:* 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.

|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'''Commands:'''* [https://searchdatacenterman7.org/linux/man-pages/man1/sed.techtarget1p.comhtml sed]* [https:/definition/shellman7.org/linux/man-script Purposepages/man1/awk.1p.html 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 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>

It is recommended to '''plan''' out on a piece of paper ===Using the purpose of the shell script.<br>Once you have planned your shell script by listing the sequence of steps,<br>you need to create a file (using a '''text editor''') that will contain your Linux commands.<br><br>'''NOTE:''' Avoid using filenames of already existing Linux Commands to avoid confusion.<br>It is recommended to include a file extension that describes the type of shell for the shell script.<br><br>sed Utility===

[[Image:shebang.png|thumb|right|200px|The '''shebang line''' <u>must</u> appear on the '''first line''' and at the '''beginning''' of the shell script.]]Since Linux shells have evolved over a period of time, using a she-bang line '''forces''' the shell script<br>to run in a '''specific shell''', which could prevent errors in case an older shell does not recognize newer features from more recent shells.<br><br>The she-bang line is a special comment at top of your shell script to run your shell script in that specific shell.<br><br>The '''shebang line''' <u>must</u> appear on the '''first line''' and at the '''beginningUsage:''' of the shell script,<br>otherwise, it will be treated as a regular comment and ignored.<br><br>

'''Setting Permissions &amp<span style="color:blue; Running a Shell Scriptfont-weight:bold;font-family:courier;">Syntax: sed [-n] 'address instruction' filename</span>'''

'''ExampleHow it Works:<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 Variables * The sed command reads all lines in Shell Scripts===the input file and will be exposed to the expression<br>(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 an instruction (operation).* If the line matches the address, then it will perform the instruction.* Lines will display be default unless the '''–n''' option is used to suppress default display<br>'''Address:'''

* Can use a line number, to select a specific line (for example: '''Definition5''')* 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

 '''Environment Variables''' [[Image:environmentsed.png|thumb|right|500px|Examples of using '''Environment''' and '''User Defined''' variables.]]Shell '''environment variablesInstruction:''' 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>(you can issue the pipeline command *'''set | moreAction''' to view all variablestake for matched line(s) Placing a dollar sign ('''$''') prior *Refer to the variable name will cause the variable to expand to the value contained in the variable.  '''User Defined Variables''' ''<b>Usertable on right-defined variablesside for list of some</bbr> are variables which can be '''created by the usercommon instructions''' and exist in the session. This means that no one can access user-defined variables that have been set by another user,<br>and when the session is closed these variables expire.''<br>Reference: https://mariadb.com/kb/en/user-defined-variables/their purpose

''Examples:'' <span style="font-family:courier;font-weight:bold">file $(ls)<br>mail -s "message" $(cat email-list.txt) < message.txt<br>echo "The current directory is $(pwd)"<br>echo "The current hostname is $(hostname)"<br>echo "The date is: $(date +'%A %B %d, %Y')"<br>  '''Math Operations:'''[[Image:math-op.png|thumb|right|275px|Common Math Operator Symbols.]]In order to make math operations work, we need to convert numbers<br>stored as '''text''' into '''binary numbers'''.<br><br>We can do this by using 2 pairs of round brackets '''(( ))'''.<br><br>Refer to the table on the right for common mathematical symbols.<br><br> ''Examples:'' <pre style="width:30%">num1=5;num2=10echo “$(($num1 + $num2))”15echo “$((num1-num2))”-5((product=num1*num2))echo “$product”50</pre> ===Using Control Flow Statements in Shell Scriptsthe awk Utility===

The special parameter '''$?Usage:''' 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). The test command can be used with control flow statements to control the sequence of a shell script.

You CANNOT use the '''<span style="color:blue;font-weight:bold;font-family:courier;">awk [-F] ''' or '''selection-criteria {action}’ file-name<''' symbols when using the test command since these are redirection symbols. Instead, you need to use options when performing numerical comparisons.Refer to the table below for test options and their purposes./span>

Refer to diagrams to the right involving some of the options used with the '''testHow It Works:''' command. Refer to the test man pages for a full list of options for the test command.

* The '''Logic Statementsawk'''command reads all lines in the input file and will be exposed to the expression (contained within quotes) for processing. A *The '''logic statementexpression''' is used to determine which Linux commands to be executed based<br>on the result of a condition (i.e. TRUE (zero valuecontained in quotes) or FALSE represents '''selection criteria''', and '''action''' to execute contained within braces '''{}'''* if selection criteria is matched, then action (non-zero value)between braces)is executed. <table align="right"><tr valign="top"><td>[[Image:logic-1.png|thumb|right|250px|Example of using * The '''–F''' option can be used to specify the default '''iffield delimiter''' logic control-flow statement.]](separator) character</td><tdbr>[[Image:loop-1eg.png|thumb|right|250px|Example of using the '''forawk –F”;”''' looping control-flow statement.]]</td></table> There are several logic statements, but we will just concentrate on the if statement.<pre style="width:20%">if test condition then command(swould indicate a semi-colon delimited input file) fi.</prebr> Refer to the diagram immediately to the right for using the '''if logic statement'Selection Criteria'' with the '''test''' command.

<br* 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 ~ /^[0-9]/'''* The '''!~''' operator tests for no match. For example: '''$2 !~ /line/'''* You can perform both numeric and string comparisons using relational operators ( '''><br''' , '''>=''' , '''<br>''' , '''<br>=''' , '''==''' , '''!=''' ).* You can combine any of the patterns using the Boolean operators '''||''' (OR) and '''&&''' (AND).* You can use built-in variables (like NR or "record number" representing line number) with comparison operators.<br>For example: '''if-else statement:NR >=1 && NR <= 5'''

[[Image:if-else.png|thumb|right|300px|Example of how an '''if-elseAction (execution):''' statement works.<br>(Image licensed under [https://creativecommons.org/licenses/by-sa/3.0/ cc])]]

Unlike using only an * Action to be executed is contained within braces '''{}'if'' statement, an * The '''if-elseprint''' statement take 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 '''two different sets of actions$0'''<br>based on represents all of the results of fields contained in the test conditionrecord (line).<br><br>* The parameters '''$1'How it Works:''<br>When the test condition returns a , '''TRUE$2''' value, then the Linux Commands between<br>'''then$3''' and … '''else$9''' statements are executedrepresent the first, second and third to the 9th fields contained within the record.<br>If * Parameters greater than nine requires the value of the test returns a parameter to be placed within braces (for example: '''FALSE${10}''' value, then the the Linux Commands between<br>the '''else${11}''' and ,'''fi${12}''' statements are executed, etc.)* You can use built-in '''variables''' (such as '''NR''' or "record number" representing line number)<br><br>eg. '''{print NR,$0}''' (will print record number, then entire record).

''Example=INVESTIGATION 1:''USING THE SED UTILITY=

<span style="font-family:courier;font-weightcolor:boldred;">num1=5<br>num2=10<br>if test $num1 –lt $num2<br>then<br> &nbsp;&nbsp;&nbsp;echo “Less Than”<br>else<br>echo &nbsp;&nbsp;&nbsp;“Greater Than or Equal to”'''ATTENTION''': Effective '''May 9, 2022''' - this online tutorial will be required to be completed by '''Friday in week 11 by midnight'''<br>fito obtain a grade of '''2%''' towards this course</span><br><br>

 '''Loop Statements''' ''A <b>loop statement</b> 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, but we will look at the '''for loop''' using a '''list'''. <pre style="width:20%">for item in list do command(s) done</pre> Refer to the diagram above and to the extreme right side for an example using the '''for loop''' with a '''list'''. =INVESTIGATION 1: CREATING A SHELL SCRIPT= <br>In this sectioninvestigation, you will learn how to create and run a manipulate text using the '''simple Bash Shell scriptsed'''utility.

# '''Login''' to your matrix accountand confirm you are located in your '''home''' directory.<br><br># Issue a Linux command to create a directory called '''confirm'sed'' 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/span>~murray.saul/uli101/data.txt<br/nowiki><br/span>You should notice that there is no output and therefore, this shell script name CAN be used.<br><br># Use a Issue the '''text editormore''' like command to quickly view the contents of the '''vidata.txt''' or 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:sed-1.png|thumb|right|300px|Issuing the '''nanop''' to create instruction without using the text file called '''hello-n'''option (to suppress original output) will display lines twice.]]<br><br>If you are using The '''p''' instruction with the nano text editor, refer '''sed''' command is used to notes on <br>'''print''' (i.e. ''display'') the contents of a text editing in a previous week in the course schedulefile.<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 '''environmentpipeline commands''' variable that contains to both display stdout to the current user's login name.<Br>In this way if you wanted screen and save to share your shell script with other users, when they run the shell scriptfiles<br>it will greet by for <u>theirconfirmation</u> username. Using of running these pipeline commands when run a ''environment variables'checking-script' makes your shell script to be more "usable" by others'' later in this investigation.<br><br># Save your editing session and exit Issue the text editorfollowing 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>Instead of issuing You can specify an '''address''' to display lines using the sed utility<br>(eg. ''line #''bash, ''' command followed by your shell script pathname as an line #s''' or range of '''line #s'argument'',).<br><br># Issue the following Linux pipeline command:<br>let<span style="color:blue;font-weight:bold;font-family:courier;">sed -n 's simply run it by its filename1 p' data.txt | tee sed-2. This is txt</span><br><br>You should see the most common method first line of running shell scriptsthe text file displayed.<br>What other command is used to only display the first line in a file?<br><br>[[Image:hello1sed-2.png|thumb|right|150px500px|Output of Using the sed command from running your to display a '''hellorange''' shell script (YourUserID is your username)of lines.]]# 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 -n '2,5 p' data./hellotxt | 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 '''You should s''' instruction is used to '''substitute''' 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 '2,5 s/TUTORIAL/LESSON/g' data.txt | tee sed-4.txt | more</span><br><br>What do you notice an error indicating you don't have permissions ? View the original contents of lines 2 to run 5 in the file'''data.txt''' file<br>You need in another shell to first add confirm that the substitution occurred.<br><br>[[Image:sed-3.png|thumb|right|500px|Using the sed command with the '''execute permissions-q''' prior option to running display up to a line number, then quit.]]The '''q''' instruction terminates or '''quits''' the execution of the shell scriptsed utility as soon as it is read in a particular line or matching pattern.<br><br># Issue the following linux Linux pipeline command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod sed '11 q' data.txt | tee sed-5.txt</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''' to select lines that match a pattern. In fact,<br>the sed command was one of the <u+x hello>first</u> Linux commands that used regular expression.<br><br>The rules remain the same for using regular expressions as demonstrated in '''tutorial 9'''<br>except the regular expression must be contained within '''forward slashes'''<br>(eg. <span style="font-family:courier;font-weight:bold;">/regexp/</span>).<br><br>[[Image:sed-4.png|thumb|right|400px|Using the sed command using regular expressions with '''anchors'''.]]# Re-run your shell scriptIssue the following Linux pipeline command: <br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/^The/ p' data./hellotxt | tee sed-6.txt</span><br><br>Did What do you shell script runnotice?<br><br># Issue the following Linux pipeline command:<br><span style="color:redblue;font-weight:bold;font-family:courier;">sed -n '/d$/ p' data.txt | tee sed-7.txt</span><br><br>What do you notice?<br><br>The '''ATTENTION:sed''' Students will 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/myscripts~uli101/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 VARIABLES IN SHELL SCRIPTS = In this sectionthe next investigation, you will learn how to use variables, positional and special parameters to assist you in creating adaptable shell scriptsmanipulate text using the '''awk''' utility.<br><br>

# 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># Use Issue a text editor Linux command to edit the shell script create a directory called '''helloawk'''<br><br># Add the following line Issue a Linux command to the <u>bottomchange</u> of to the file:<br><span style="font-family:courier;font-weight:bold;">echo "The current shell '''awk''' directory and confirm you are using is: $(ps -o cmd= -p $$|cut -dlocated in the '''awk'' ' -f1)"directory.</spanbr><br>Let's download a database file that contains information regarding classic cars.<br><br># Issue the following linux command ('''NOTE:copy and paste''' This command displays the '''name''' of the ''shell'' that the shell script is running in.to save time):<br>The command within <span style="color:blue;font-familyweight:courierbold;font-weightfamily:boldcourier;">$( )wget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/cars.txt</nowiki></span> uses a technique known as '''command substitution'''.<br<br><br># Issue the following linux '''cat''' command to change to quickly view the contents of the '''Bourne Shellcars.txt''':file.<br><span style=br>The "color:blue;font-weight:bold;font-family:courier;'''print'''"action (command) is the <u>shdefault</spanu>action of awk to print<br><br>You should notice your shell prompt changed all selected lines that indicates that you are in match a different shell'''pattern'''.<br><br>[[Image:hello2.png|thumb|right|275px|Changing the Bourne shell and running shell script This '''action''' (contained in braces) can provide more options<br>such as printing '''withoutspecific fields''' of selected lines (or records) from a '''She-bang''' linedatabase.<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 run your shell script display all lines (i.e. records) in the ''Bourne Shell'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./hellotxt</span><br><br>You should see that you are currently running the shell script "We will use '''shpipeline commands'''" that 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><br>an error may occur if you include a '# Issue the following linux pipeline command all to display records<br>in the '''cars.txt'NEWER'' shell feature database that contain the pattern (i.e.g. make) '''ford'Bash Shell'') in your shell script,:<br>but run it in an ''OLDER<span style="color:blue;font-weight:bold;font-family:courier;">awk '/ford/' shell (ecars.g. ''Bourne Shell'')txt | tee awk-1.txt</span><br><br>What do you notice? You can add a should notice ALL lines displayed <u>without</u> using '''special commentsearch criteria''' to the BEGINNING of the .<ubr>FIRST line</u> of your shell script to<br>You can use ''builtin'force''' it to run in 'variables''' with the shell you want (for example: the Bash shell)'''print''' command for further processing.<br>We will discuss the following variables in this tutorial:<br> # Edit your '''hello''' shell script using a text editor.<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="font-family:courier;fontbr>'''NR''' -weight:bold;">#!/bin/bash</span>Record Number (order in database)<br><br>This is referred to as a '''sheNF''' -bang line'''. It forces this script to be run Number of fields in the '''Bash Shell'''.current record<br><br>When For a listing of more variables, please consult your Bash Shell script finishes execution, you are returned to your current shell that you are using<br>(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''', '''year''' a , '''She-bangquantity''' line (forcing script to run and price<br>in the '''Bashcars.txt''' shell).]]# database for makes of '''Savechevy''' your editing changes and '''exit''' 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 '/chevy/ {print $2,$3,$4,$5}' cars./hellotxt | 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 pipeline command to rename your shell script file:<br><span style="color:blue;font-weight:bold;font-family:courier;">mv hello hello.bash</span>display all '''plymouths''' ('''plym''')<br><br># Run your renamed shell script for confirmation by issuingby '''model name''', '''price''' and '''quantity''':<br><span style="color:blue;font-weight:bold;font-family:courier;">.awk '$1 ~ /helloplym/ {print $2,$3,$4,$5}' cars.bashtxt | tee awk-3.txt</span><br><br># Enter the following linux command to You can also use '''exitcomparison operators''' the ''Bourne shell'' and return to your ''Bash shell'':to specify conditions for processing with matched patterns<br>when using the awk command. Since they are used WITHIN the awk expression,<br><span style="color:blue;font-weight:bold;font-family:courier;">exit</span>they are not confused with redirection symbols<br><br>Let's use some ''[[Image:awk-3.png|thumb|right|400px|Using the awk command to display results based on 'ENVIRONMENT variables''' in our Bash Shell script.<br><br># Use a text editor to edit the shell script called comparison operators'''hello.bash]]'''<''' &nbsp;&nbsp;&nbsp;&nbsp;Less than<br>'''<=''' &nbsp;&nbsp;Less than or equal<br># Add the following lines to the <u'''>bottom</u> of the file:''' &nbsp;&nbsp;&nbsp;&nbsp;Greater than<br><span style'''>="font-family:courier''' &nbsp;font-weight:bold&nbsp;"Greater than or equal<br>echo'''==''' &nbsp;&nbsp;Equal<br>echo "The current directory location is: $PWD"'''!=''' &nbsp;&nbsp;&nbsp;Not equal<br>echo "The current user home directory is: $HOME"<br>echo</span><br><<br># Save your editing changes and exit your text editor.<br><br># Run your renamed shell script for confirmation by issuing:<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./hello.bashtxt | tee awk-4.txt</span><br><br>Take time to view the output and the values of the environment variables.<br>What do you notice?<br><br># Issue the following linux pipeline command to add your current directory to the display display '''PATHprice''' environment variable:,<br><span style="color:blue;font-weight'''quantity''', '''model''' and '''car make''' of vehicles whose '''prices are less than $5,000''':bold;font<br><span style="color:blue;font-weight:bold;font-family:courier;">PATH=awk '$PATH:.5 </span><br5000 {print $5,$4,$2,$1}' cars.txt | tee awk-5.txt</span><br>[[Image:hello4.png|thumb|right|330px|Running <ubr>modified</u> '''hello.bash''' Bash shell script by entering by '''filename''' only.]]# # Issue the following linux pipeline command to confirm that display the current directory '''"."car make''' has been added to ,<br>'''year''' and '''quantity''' of cars that '''begin''' with the '''PATHletter 'f'''' environment variable:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo awk '$PATH<1 ~ /^f/span>{print $1,$2,$4}' cars.txt | tee awk-6.txt<br/span><br># Issue the following to run your Bash shell script just by name:<br><span style="color[[Image:blue;fontawk-weight:bold;font-family:courier;">hello4.bash</span><br>png|thumb|right|400px|Using the awk command to display combined search results based on '''compound operators'''.]]Combined pattern searches can be made<br>Did your Bash shell script run?by using '''compound operator''' symbols:<br><br># Exit your Matrix session, '''&&''' &nbsp;&nbsp;&nbsp;&nbsp;(and log back into your Matrix session.)<br><br># Re-run the '''hello.bash||''' shell script by just using the name.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(or)<br><br>What did you notice?<br><br>The setting of # Issue the following linux pipeline command to list all '''PATHfords''' environment variable only worked in the current session only.<br>If you exit the current Matrix sessionwhose '''price is greater than $10, then the recently changed settings for environment variables will be lost.000''':<br>You will in a <u>future</uspan style="color:blue;font-weight:bold;font-family:courier;"> tutorial how to set environment variables in awk '$1 ~ /ford/ && $5 > 10000 {print $0}''startcars.txt | tee awk-up''' files7.txt</span><br><br># Issue the following linux command ('''copy and paste''' to save time):<br><span style="color:redblue;"font-weight:bold;font-family:courier;">wget <nowiki>'''ATTENTIONhttps:''' Students will get FRUSTRATED when performing their '''assignment 3''' when their Bash shell scripts have errors//ict. One major cause is the senecacollege.ca/~murray.saul/uli101/cars2.txt</nowiki></span><br><br># Issue the OUTPUT of their Bash shell script when run does not '''EXACTLY matchcat''' command to quickly view the required output for contents of the correct Bash shell script. This requires that you CAREFULLY '''readcars2.txt''' the requirements of your Bash shell script and create it to the EXACT specifications</span>file.<br><br># Issue the following Linux linux pipeline command to run a checking script:display the '''year'''<br><span style="color:blue;font-weightand '''quantity''' of cars that '''begin''' with the '''letter 'f'''' for the '''cars2.txt''' database:<br><span style="color:boldblue;font-weight:bold;font-family:courier;">bash awk '$1 ~ /home^f/murray{print $2,$4}' cars2.saul/myscripts/week10txt | tee awk-check-2 | more8.txt</span><br><br>If What did you encounter errors, make corrections and notice?<br><br>The problem is that the '''cars2.txt'''redatabase separates each field by a semi-runcolon (''';' the checking script until you<br>receive a congratulations message, then you can proceed.'') <bru>instead<br/u>Let's create a Bash shell script that contain of '''user-created variablesTAB'''.<br><br># Use a text editor to create a Bash shell script called '''user-variablesTherefore, it does not recognize the second and fourth fields.bash'''<br><br># Add the following lines You need to issue awk with the beginning of -F option to indicate that this file:'s fields are separated (delimited) by a semi-colorn.<br><span style="font-family:courier;font-weight:bold;"br>#!/bin/bashIssue the following linux pipeline command to display the '''year'''<br>read -p "Enter your Full Name: " name<br>read -p "Enter your age (in years)and '''quantity''' of cars that '''begin''' with the '''letter 'f'''' for the '''cars2.txt''' database: " age<br>echo <span style="Hello $name color:blue;font-weight:bold;font- You are $age years oldfamily:courier;"</span><brawk -F";" '$1 ~ /^f/ {print $2,$4}' cars2.txt | tee awk-9.txt</span><br># Save your editing changes and exit your text editor.<br>What did you notice this time?<br>[[Image<br># Issue the following to run a checking script:<br><span style="color:userblue;font-variable1.png|thumb|right|300px|Prompting user to enter data via the '''read weight:bold;font-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.the checking script until you<br><br># 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 did 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;">receive a congratulations message, then you 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>

:In the next investigationThe purpose of this section is to obtain '''extra practice''' to help with '''quizzes''', you will learn to use your '''command substitutionmidterm''' , and your '''math operationsfinal exam''' in your shell scripts.

=INVESTIGATION 3Here is a link to the MS Word Document of ALL of the questions displayed below but with extra room to answer on the document tosimulate a quiz: COMMAND SUBSTITUTION / MATH OPERATIONS=

In this section, you will learn how to use '''command substitution''' and '''math operations''' in your shell scriptshttps://ict.senecacollege.ca/~murray.saul/uli101/uli101_week11_practice.docx

Command Substitution is a method of running a Linux command that provides '''stdoutReview Questions:'''<br>that is used as '''argument(s)''' for <u>another</u> Linux command.

''For example'Part A:Display Results from Using the sed Utility'''

<span style="fontNote the contents from the following tab-family:courier;font-weightdelimited file called '''~murray.saul/uli101/stuff.txt''':bold;">echo "The current date and time is: $(datethis file pathname exists for checking your work)"</span>

'''Perform Write the Following Stepsresults of each of the following Linux commands for the above-mentioned file:'''

# <span style="font-family:courier;font-weight:bold">sed -n '3,6 p'~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed 'Math Operations4 q'~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed '/the/ 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>

'''Perform Write a single Linux command to perform the Following Steps:'''specified tasks for each of the following questions.

# Write a Linux sed command to display only lines 5 to 9 for the file:In '''~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 next investigation, you will use file: '''control-flow statements~murray.saul/uli101/stuff.txt''' <br><br># Write a Linux sed command to allow your shell scripts 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 perform differently under different situations: '''~/results.txt'''<br><br>

: Before learning about logic and loop control-flow statements, you need to first learn about issuing test conditions using the '''test''' command.<br><br># Confirm that you are located in your '''home''' directory in your Matrix account.<br><br># Issue Write the following linux commands at the Bash shell prompt to assign values to several variables:<br><span style="color:blue;font-weight:bold;font-family:courier;">course="ULI101"<br>number1=5<br>number2=10</span><br><br># Issue the following linux command to test a condition:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $course = "ULI101"</span><br><br>The '''$?''' variable is used to store an exit status results of the previously command issued (including the test command).<br>If the exit status is '''zero''', then it indicates a TRUE value and if the status is '''non-zero''', then it indicates a FALSE value.<br><br># Issue the following linux command to view the status of the previously-issued '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $?</span><br><br>Based on its value, is the result TRUE or FALSE?<br><br># Issue the following linux command to test another condition:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $course = "uli101"</span><br><br># Issue the following linux command to view the status each of the previously-issued '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $?</span><br><br>The value is non-zero (FALSE) since UPPERCASE characters are different than lowercase characters.<br><br># Issue the following linux command to test another condition:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $course != "uli101"</span><br><br># Issue a linux command to display the value of '''$?'''. What is the result? Why?<br><br># Issue the following linux command to test a condition involving numbers:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $number1 > $number2</span><br><br># Issue a linux command to display the value of '''$?'''. '''NOTE:''' You will notice that something is '''wrong'''.<br>The exit status '''$?''' shows a zero (TRUE) value, but the number 5 is definitely NOT greater than 10.<br>The problem is that the symbols '''&lt;''' and '''&gt;''' are interpreted as REDIRECTION symbols!<br><br># To prove this, issue the following linux command :<br><span style="color:blue;font-weight:bold;font-family:courier;">ls 10</span><br><br>You should notice a file called "'''10'''". The incorrectly issued '''test''' command used redirect to create an empty file instead,<br> which indeed succeeded just giving a TRUE value!<br><br>To prevent problems when issuing the '''test''' command when comparing numbers, you can use the following options:<br>'''-lt''' (&lt;), '''-le''' (&lt;&#61;), '''-gt''' (&gt;), '''-ge''' (&gt;&#61;;), '''-eq''' (&#61;), '''-ne''' (!&#61;)<br><br># Issue the correct linux command to properly test both values:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $number1 -gt $number2</span><br><br># Issue a linux command to display the value of '''$?'''.<br>You should notice that the exit status value is now FALSE which is the correct result.<br><br># The '''test''' command can be abbreviated by the square brackets '''&#91; &#93;''' which contains the '''test''' condition<br>within the square brackets. You need to have spaces between the brackets and the test condition;<br>otherwise, you will get a test error.<br><br># To generate a '''test error''', copy and paste the following '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">&#91;$number1 -gt $number2&#93;</span><br><br>The reason Linux commands for the error was that you need '''spaces''' between the '''square brackets''' and the '''test condition'''.<br><br># Copy and paste the following (correct) '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">&#91; $number1 -gt $number2 &#93;</span><br><br># Issue a command to view the value of the '''exit status''' of the previously issued '''test''' command.<br>You should notice that is works properly.<br><br>Now that we have learned how to test conditions, let's learn about '''controlabove-flow''' statements.<br><br>'''Logic statements''' are used to create '''different paths''' or directions that the shell script will take<br>based on the <u>result</u> of the '''test condition'''. In this tutorial,<br>we will only focus on the '''if''' and '''if-else''' logic statement.<br><br># Use a text editor like vi or nano to create the text mentioned file called '''if-1.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-1.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br># Enter the following lines in your shell script:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>num1=5<br>num2=10<br>if [ $num1 -lt $num2 ]<br>then<br>&nbsp;&nbsp;&nbsp;echo "num1 is less than num2"<br>fi</span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').<br><br>[[Image:if-1.png|thumb|right|200px|Output of a shell script using the '''if''' control-flow statement.]]# Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x if-1.bash</span><br><br># Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./if-1.bash</span><br><br>Confirm that the output indicated a correct result.<br><br># Use a text editor like vi or nano to create the text file called '''if-2.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-2.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br># Enter the following lines in your shell script:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>read -p "Enter the first number: " num1<br>read -p "Enter the second number: " num2<br>if [ $num1 -gt $num2 ]<br>then<br>&nbsp;&nbsp;&nbsp;echo "The first number is greater than the second number."<br>fi</span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').<br><br>[[Image:if-2.png|thumb|right|320px|Output of a shell script using the '''read''' command '''if''' control-flow statement.]]# Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x if-2.bash</span><br><br># Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./if-2.bash</span><br><br>Confirm that the output indicated a correct result.<br><br>What happens when you enter a first number that is less than or equal to the second number? Let's use an '''if-else''' statement to provide an appropriate alternative<br>if the condition is FALSE.<br><br># Use a text editor like vi or nano to create the text file called '''if-3.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-3.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br># Enter the following lines in your shell script:<br><span style="font-family:courier;font-weight:bold">#!/bin/bash<br>read -p "Enter the first number: " num1<br>read -p "Enter the second number: " num2<br>if [ $num1 -gt $num2 ]<br>then<br>&nbsp;&nbsp;&nbsp;echo "The first number is greater than the second number."<br>else<br>&nbsp;&nbsp;&nbsp;echo "The first number is less than or equal to the second number."<br>fi</span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').<br><br>[[Image:if-3.png|thumb|right|330px|Output of a shell script using the '''if-else''' control-flow statement.]]# Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x if-3.bash</span><br><br># Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./if-3.bash</span><br><br>What do you notice? Try running the script several times with numbers different and equal to each other to confirm that the shell script works correctly.<br><br>Let's learn how to use a simple loop with shell scripting. In this tutorial, we will only focus on one simple use with the '''for''' loop.<br><br># Use a text editor like vi or nano to create the text file called '''for-1.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi for-1.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br># Enter the following lines in your shell script:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>echo<br>for x in 5 4 3 2 1<br>do<br>&nbsp;&nbsp;&nbsp;echo $x<br>done<br>echo "blast-off!"<br>echo</span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').<br><br>[[Image:for-1.png|thumb|right|125px|Output of a shell script using the '''for''' loop with a '''list'''.]]# Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x for-1.bash</span><br><br># Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./for-1.bash</span><br><br># Use a text editor like vi or nano to create the text file called '''for-2.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi for-2.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br># Enter the following lines in your shell script:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>echo<br>for x<br>do<br>&nbsp;&nbsp;&nbsp;echo $x<br>done<br>echo "blast-off!"<br>echo</span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').<br><br># Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x for-2.bash</span><br><br>[[Image:for-2.png|thumb|right|175px|Output of a shell script using the '''for''' loop <u>without</u> a '''list'''.]]# Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./for-2.bash 10 9 8 7 6 5 4 3 2 1</span><br><br>How does this differ from the previous shell script?<br><br>You will learn in a couple of weeks more examples of using loop statements.<br><br>Let's run a '''checking-script''' to confirm that both your '''for-1.bash''' and '''for-2.bash'''<br>Bash shell scripts exist, have execute permissions, and when run, produce<br>the same OUTPUT as required in this tutorial's instructions.<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/myscripts/week10-check-4 | more</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>Let's create a Bash shell script that contain '''user-created variables'''.<br><br># After you complete the Review Questions sections to get additional practice, then work on your '''online assignment 3''',<br>'''sections 2 and 3''' labelled '''Interactive Shell Environment''' and '''Introduction To Scripting (phone)'''.<br><br>

The purpose of this section is to obtain '''extra practice''' to help with '''quizzes'''# <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, your '''midterm''', and your '''final exam'''$2}’ ~murray.saul/uli101/stuff.txt</span><br><br>

:'''Walkthru #1Part D:Writing Linux Commands Using the awk Utility'''

:WRITE OUTPUT FROM ISSUING::'''Write a single Linux command to perform the specified tasks for each of the following questions./walkthru1.bash'''

# 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>#2Write 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>