=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''' shell scriptswith 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" |'''Slides:''':<ul><li>Week 10 11 Lecture 1 Notes:<br> [https[Media://matrix.senecacollege.ca/~chris.johnson/ULI101/ULI101-Week10Week11.1.pdf | PDF]] | [https://matrix.senecacollege.ca/~chris.johnson/ULI101/ULI101-Week10Week11.1.pptx PPTX]<br/li><li>Week 10 11 Lecture 2 Notes:</li><libr> [https[Media://matrix.senecacollege.ca/~chris.johnson/ULI101/ULI101-Week10Week11.2.pdf | PDF]] | [https://matrix.senecacollege.ca/~jason.carman/slides/ULI101-Week10Week11.2.pptx PPTX] <br></li></ul>

| style="padding-left:15px;" |'''Shell ScriptingText 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]

'''Variables:'''* [https://opensource.com/article/19/8/what-are-environment-variables Environment]* [https://www.linuxtechi.com/variables-in-shell-scripting/#:~:text=User%20Defined%20Variables%3A,like%20a%20real%20computer%20program. User Defined]* [http://osr600doc.xinuos.com/en/SDK_tools/_Positional_Parameters.html#:~:text=A%20positional%20parameter%20is%20a,up%20to%20nine%20positional%20parameters. Positional Parameters]C'''ommands / Techniques:'''* [http://linuxcommand.org/lc3_man_pages/readh.html read]* [https://man7.org/linux/man-pages/man1/readonly.1p.html readonly]* [https://www.gnu.org/software/bash/manual/html_node/Command-Substitution.html Command Substitution]| style="padding-left:15px;"|'''Control Flow StatementsCommands:'''* [https://en.wikipediaman7.org/wikilinux/Control_flow Purpose]* [https:man-pages/man1/wwwsed.computerhope1p.com/unix/test.htm test commandhtml sed]* [https://ryanstutorialsman7.netorg/bash-scripting-tutoriallinux/bashman-if-statements.php#:~:text=If%20statements%20(and%2C%20closely%20related,conditions%20that%20we%20may%20set. if statement]* [https:pages/man1/wwwawk.tutorialspoint1p.com/unix/if-else-statement.htm if-else statement]* [https://www.cyberciti.biz/faq/bash-for-loop/#:~:text=A%20'for%20loop'%20is%20a,files%20using%20a%20for%20loop. 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 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>

[[Image:shebang.png|thumb|right|200px|The '''shebang line''' <u>must</u> appear on ===Using 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<br>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<br>in a specific shell.<br><br>'''NOTE:''' The '''shebang line''' <u>must</u> appear on the '''first line''' and at the '''beginning''' of the shell script,<br>otherwise, it will be treated as a regular comment and ignored.<br><br>sed Utility===

To run your shell script by name, you need to assign '''execute permissionsUsage:''' for the user.<br>To run the shell script, you can '''execute''' the shell script using a ''relative'', ''absolute'', or ''relative-to-home'' pathname

''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>

'''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 * The sed command reads all lines in the diagram displayed on input file and will be exposed to the right-side.expression<br><br>You can issue the pipeline command <span style="font-family:courier;font-weight:bold">set | more</span><br>to view all variables(i.e.<br><br>Placing a dollar sign "<span style="font-family:courier;font-weight:bold">$</span>" prior to the variable name will cause the variable to expand to the value area contained in the variable.  '''User Defined Variables''' <b>User-defined variables</b> are variables that can be used in the shell script for '''customized''' purposes.<br><br>Data can be stored and removed within quotes) one line at a variable using an '''equal sign''' (no spaces on either side of equal sign)time.<br><br>* The '''read''' command expression can be used to prompt the user to enter data into a variable. The '''readonly''' command will prevent<br>the current value of the variable for the remainder of the execution of a shell script.<br><br> '''Positional Parameters and Special Parameters''' [[Image:positional.png|thumb|right|220px|Examples of using '''positional''' and '''special''' parameters.]]A '''positional parameter''' is a variable within a shell program; its value is set from arguments contained in a shell script single quotes or using the '''set''' commanddouble quotes.Positional parameters are numbered * The expression contains an address (match condition) and their values are accessed by using<br>a preceding "'''$'''" an instruction (eg. '''$1''', '''$2''', '''$3''', etc.operation). The positional parameter '''$0''' refers to<br>either * If the '''name of shell''' where command was issued, or '''filename of shell script''' being executed.<br>If using '''positional parameters''' greater than '''9'''line matches the address, then you need to include number within braces.<br><br>Examples: '''echo ${10}''', '''ls ${23}'''<br><br> The '''shift''' command can be used with positional parameters to shift positional parameters<br>to the left by one or more positionsit will perform the instruction. There are a couple of ways to assign values as positional parameters::*Use Lines will display be default unless the '''set–n''' command with the values as argument after the set command:*Run a shell script containing arguments   There are a group of '''special parameters''' that can be option is used for shell scripting.<br>A few of these special parameters and their purpose are displayed below:<br>'''$*''' , '''“$*”''' , '''"$@"''' , '''$#''' , '''$?'''<br><br> === Command Substitution / Math Operations ===to suppress default display

'''Command SubstitutionAddress:'''

[[Image* Can use a line number, to select a specific line (for example:for-command-substitution.png|thumb|right|300px|Example of how a '''for loop with command substitution5''' works.]])<i>* Can specify a range of line numbers (for example: '''Command substitution5,7''' is )* Regular expressions are contained within forward slashes (e.g. /regular-expression/)* Can specify a facility regular expression to select all lines that allows a command<br>to be run and its output to be pasted back on the command line as arguments to another commandmatch a pattern (e.<g '''/i> Reference: https://en^[0-9].wikipedia.org*[0-9]$/wiki/Command_substitution<br><br>''') * If NO address is present, the instruction will apply to ALL lines

<span style="font-family[[Image:courier"><b>command1 $(command2)</b><br>or<br><b>command1 `command2`</b></span><br><br>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

<pre style="width:30%">num1=5;num2=10echo “$(($num1 + $num2))”15echo “$((num1-num2))”-5((productUsing the awk Utility===num1*num2))echo “$product”50</pre><br>

===Control Flow Statements===<br> <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 Statements''' are used to make your shell scripts<br>more '''flexible''' and can '''adapt''' to changing situations.<br><br>In order to use control flow statements, you need to test a condition to get<br>'''TRUE''' (zero value) or '''FALSE''' (non zero value). This can be done two ways:<ul><li>Run a command to get the exit status (<span style="font-family:courier;font-weightUsage:bold;">$?</span>)</li><li>Use the '''test''' command</li></ul><br>Refer to the diagrams on the right to see how to use the test command.<br><br>

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

A '''logic statement''' is used to determine which Linux commands<br>are executed basedon the result of a conditionHow It Works:<br>'''TRUE''' (zero value) or '''FALSE''' (non-zero value).

[[Image:logic-1* The '''awk''' 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.png|thumb|right|210px|Example of using * The '''–F''' option can be used to specify the default '''field delimiter''' (separator) character<br>eg. '''ifawk –F”;”''' logic control (would indicate a semi-flow statementcolon delimited input file).]]

There are several logic statements, but we will just concentrate on the if statement.<pre style="width:20%">if test condition then command(s) fi</pre> Refer to the diagram to the right for using the '''if logic statementSelection 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:logic-2.png|thumb|right|210px|Example of how an '''if-else''' control-flow statement.]] Unlike using an ''if'' statement, an '''if-else''' statement take '''two different sets of actionsAction (execution):'''<br>based on the results of the test condition.<br><br>

* Action to be executed is contained within braces ''Example'{}'''* 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).* The parameters '''$1''', '''$2''', '''$3''' … '''$9''' represent the first, second and third to the 9th fields contained within the record. * Parameters greater than nine requires the value of the parameter to be placed within braces (for example: '''${10}''','''${11}''','''${12}''', etc.)* You can use built-in '''variables''' (such as '''NR''' or "record number" representing line number)<br>eg. '''{print NR,$0}''' (will print record number, then entire record).

<pre style="widthINVESTIGATION 1:20%">if test condition then command(s) else command(s) fi</pre>USING THE SED UTILITY=

'''Loop Statements'''[[Image:loop-1.png|thumb|right|210px|Example of using the '''for''' looping control-flow statement.]]''A <b>loop statement</b> is a series of steps or sequence of statements executed repeatedly<br>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'''.<br><br> =INVESTIGATION 1: CREATING A SHELL SCRIPT= <span style="color:red;">'''ATTENTION''': Effective '''May 9, 2022''' - this online tutorial will be required to be completed by '''Friday in week 12 by midnight'''<br>to obtain a grade of '''2%''' towards this course</span><br><br> In this investigation, you will learn how to create and run a manipulate text using the '''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 '''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''' directory and confirm that you are located in the '''sed''.<br>Let's first look at selecting an appropriate filename for your shell scriptdirectory.<br><br># Issue the following linux Linux command to check if download the filename called data.txt file<br>('''hellocopy and paste'''<br>already exists as a commandto save 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>The output from this # Issue the '''more''' command should indicate that to quickly view the contents of the shell did NOT'''data.txt''' file.<br>find any directories that contained this filename that could representWhen finished, exit the more command by pressing the letter <br>a commandspan style="color:blue;font-weight:bold;font-family:courier; therefore, this shell script name CAN be used.<br">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 scriptLinux 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 '''s login namechecking-script''' later 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:<ubr>their<span style="color:blue;font-weight:bold;font-family:courier;">sed -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 '''address'Environment variables'' make your shell script adaptable by ALL users.to display lines using the sed utility<br><br>(eg. ''line # '', '''line #s''Save'or range of '' your editing session and 'line #s''exit').<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 editorfile displayed.<br>What other command is used to only display the first line in a file?<br>Instead of issuing <br>[[Image:sed-2.png|thumb|right|500px|Using the sed command to display a '''bashrange''' of lines.]]# Issue the following Linux pipeline command followed by your shell script pathname as an :<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '2,5 p'argument'',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>letThe '''s simply run it by its filename. This ''' instruction is used to '''substitute''' text<br>(a similar to method was demonstrated in the most common method of running shell scriptsvi editor in tutorial 9).<br><br># Issue the following Linux pipeline command:<br><table alignspan style="rightcolor:blue;font-weight:bold;font-family:courier;">sed '2,5 s/TUTORIAL/LESSON/g' data.txt | tee sed-4.txt | more</span><tr valign="top"br><br>What do you notice? View the original contents of lines 2 to 5 in the '''data.txt''' file<br>in another shell to confirm that the substitution occurred.<br><tdbr>[[Image:nosed-execute3.png|thumb|right|230px500px|Using the sed command with the '''-q''' 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.<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed '11 q' data.txt |An 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 '''error messageregular expressions''' will appear when trying to run select lines that match a shell script by name pattern. In fact,<br>the sed command was one of the <u>first</u> Linux commands that does NOT have used regular expression.<br><br>The rules remain the same for using regular expressions as demonstrated in '''executetutorial 9''' permissions<br>except the regular expression must be contained within '''forward slashes'''<br>(eg.]]<span style="font-family:courier;font-weight:bold;">/regexp/</tdspan> ).<br><tdbr>[[Image:hello1sed-4.png|thumb|right|150px400px|Output from running your Using the sed command using regular expressions with '''helloanchors''' shell script (YourUserID representing .]]# Issue the following Linux pipeline command:<ubr>your<span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/u> username)^The/ p' data.txt | tee sed-6.]]txt</tdspan></tablebr><br>What do you notice?<br><br># 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 '/d$/ p' data./hellotxt | tee sed-7.txt</span><br><br>You should What do you notice an ?<br><br>The '''ERROR messagesed''' indicating you donutility can also be used as a 't have permissions to run the file. To fix this, you need to<br>''filter'add execute permissions''' prior to running the shell scriptmanipulate text that<br>was generated from Linux commands.<br><br># Issue [[Image:sed-5.png|thumb|right|400px|Using the following linux sed command to with '''addpipeline'''<br>execute permissions for your shell scriptcommands.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x hellowho | sed -n '/^[a-m]/ p' | tee sed-8.txt | more</span><br><br>What did you notice?<br><br># Issue the following to run your shell scriptLinux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | sed -n '/txt$/ p' | tee sed-9./hellotxt</span><br><br>Did your shell script runWhat 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;">~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: SHE-BANG LINE / VARIABLES / PARAMETERS=In the next investigation, you will learn how to manipulate 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>Let's demonstrate that the Unix/Linux shell stores numbers as ascii text<br>which can cause problems when performing math operations.# Issue a Linux command to create a directory called '''awk'''<br><br># Issue the following a Linux command from the shell:to <bru>change<span style="color:blue;font-family:courier;font-weight:bold">echo "1 + 2"</span>/u> to the '''awk''' directory and confirm you are located in the '''awk''' directory.<br><br>What did you notice?Let's download a database file that contains information regarding classic cars.<br><br># To demonstrate Issue the need for the '''following linux command (( ))''' construct, issue the following Linux commands (using the copy and paste''math construct''to save time):<br><span style="color:blue;font-familyweight:courierbold;font-weightfamily:boldcourier;">echo "$((1 + 2))"wget <nowiki>https:/span><br/ict.senecacollege.ca/~murray.saul/uli101/cars.txt</nowiki><br/span>What did you notice?<br>The <span style="font-family:courier;font-weight:bold"br>(( ))</span> construct converted values # Issue the '''1cat''' and '''2''' from ''text'' command to quickly view the contents of the '''binary numberscars.txt'''file.<br><br>The "'''$print''' in front " action (command) is the <u>default</u> action of the construct awk to print<br>all selected lines that match a '''expandspattern''' the result of the calculation.<br><br># Issue the following Linux commands demonstrating other types of math calculations:This '''action''' (contained in braces) can provide more options<br>such as printing '''specific fields''' of selected lines (or records) from a database.<br><span style="colorbr>[[Image:blue;fontawk-family:courier;font-weight:bold">echo "$((2 - 3)1.png|thumb|right|400px|Using the awk command to display matches of the pattern '''ford'''.]]# Issue the following linux command all to display all lines (i.e. records)in the '''cars.txt''' database that matches the pattern (or "</span>make") called '''ford''':<br><span style="color:blue;font-familyweight:courierbold;font-weightfamily:boldcourier;">echo "$((2 * 3))"awk '/ford/ {print}' cars.txt</span><br><span style="color:blue;font-family:courier;font-weight:bold"br>We will use '''pipeline commands''' to both display stdout to the screen and save to files for <u>echo "$((2 / 3))"confirmation</u> of running these pipeline commands when run a '''checking-script''' later in this investigation.</span><br><span style="color:blue;font-family:courier;font-weight:bold">echo "$((2 ** 3))"</spanbr><br># Issue the following linux pipeline command all to display records<br>in the '''NOTE:cars.txt''' You may notice database that contain the pattern (i.e. make) '''dividingford''' '''2''' by '''3''' shows a '''zero''' result. To perform decimal calculations would require:<br>the use the '<span style="color:blue;font-weight:bold;font-family:courier;">awk '/ford/'cars.txt | tee awk''' or '''bc''' Linux commands (we will '''NOT''' cover that method to work with ''decimal numbers'' in this course)-1.txt</span><br><br>What do you notice? You can use the should notice ALL lines displayed <u>without</u> using '''search criteria'math construct'' with variables as well.<br><br># Issue the following Linux commands demonstrating using the You can use ''math constructbuiltin'' with '''variables''':<br><span style="color:blue;font-family:courier;font-weight:bold">num1=34</span>with the '''print''' command for further processing.<br><span style="color:blue;font-family:courier;font-weightWe will discuss the following variables in this tutorial:bold">num2=12</spanbr><br><span style="color[[Image:blue;fontawk-family:courier;font2.png|thumb|right|400px|Using the awk command to print search results by '''field number'''.]]'''$0''' -weight:bold">echo "$((num1 * num2Current record (entire line))"</span><br>'''$1''' - First field in record<br>What did you notice?'''$n''' - nth field in record<br><'''NR''' - Record Number (order in database)<br>You can create variables and assign them values in the ''math construct'NF''' as well- 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 commands demonstrating using linux pipeline command to display the math construct with '''variablesmodel''', '''year''', '''quantity''':and price<br><span style="color:blue;font-family:courier;font-weightin the '''cars.txt''' database for makes of '''chevy''':bold">num1=5</span><br><span style="color:blue;font-familyweight:courierbold;font-weightfamily:boldcourier;">num2=awk '/chevy/ {print $2,$3,$4,$5}' cars.txt | tee awk-2.txt</span><br><span style="color:blue;font-family:courier;font-weight:bold">((result = num1 ** num2))br>Notice that a '''space''' is the delimiter for the fields that appear as standard output.</spanbr><br><span style="color:blue;font-family:courier;font-weight:bold">echo "The result The '''tilde character''' '''~''' is: $result"</span>used to search for a pattern or display standard output for a particular field.<br><br># Use a text editor Issue the following linux pipeline command to create a Bash shell script called display all '''plymouths''' ('''dog-years.bashplym''')<br><br># Add the following lines to the beginning of this fileby '''model name''', '''price''' and '''quantity''':<br><span style="color:blue;font-familyweight:courierbold;font-weightfamily:boldcourier;">#!awk '$1 ~ /binplym/bash{print $2,$3,$4,$5}' cars.txt | tee awk-3.txt</span><br>echo<br>dogFactor=7You can also use '''comparison operators''' to specify conditions for processing with matched patterns<br>read -p "Please enter your age (in years): " humanYearswhen using the awk command. Since they are used WITHIN the awk expression,<br>((dogYears = humanYears * dogFactor))they are not confused with redirection symbols<br>echo "You age in dog-years is: $dogYears"<br>echo<br></span><br># Save your editing changes and exit your text editor.<br><br>[[[[Image:mathops1awk-3.png|thumb|right|275px400px|Output of a shell script with math operations using Using the awk command to display results based on '''math constructcomparison operators'''.]]# Issue the '''chmod<'''' command to add execute permissions &nbsp;&nbsp;&nbsp;&nbsp;Less than<br>for the user for the '''dog-years.bash<=''' file.<br>&nbsp;&nbsp;Less than or equal<br># Issue the following to run the '''dog-years.bash>''' Bash shell script:&nbsp;&nbsp;&nbsp;&nbsp;Greater than<br><span style'''>="color:blue''' &nbsp;font-weight:bold&nbsp;font-family:courier;">./dog-years.bash</span>Greater than or equal<br>'''==''' &nbsp;&nbsp;Equal<br>Enter <ubr>your</u> age to see what happens.'''!=''' &nbsp;&nbsp;&nbsp;Not equal<br><br># Issue the following linux pipeline command to run a checking script:<br><span style="color:blue;fontdisplay 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;">~uli101/week10awk '$5 < 5000 {print $1,$2,$4,$5}' cars.txt | tee awk-check-3 | more4.txt</span><br><br>If What do you encounter errors, make corrections and '''re-run''' the checking script until you<br>receive a congratulations message, then you can proceed.<brnotice?<br><br> :In # Issue the next investigation, you will use following linux pipeline command to display display '''control-flow statementsprice''' to allow your shell scripts<br>to perform differently under different situations.<br>,<br> =INVESTIGATION 4: CONTROL FLOW STATEMENTS =<br>In this investigation, you will learn how to use '''control-flow statementsquantity'''<br>to make your shell script , ''behave differently'model' under ''different situations or conditionsand '''.  car make'''Perform the Following Steps:of vehicles whose '''<br><br># Confirm that you prices are located in your less than $5,000'''home''' directory in your Matrix account.<br><br># Issue 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"awk '$5 <br>number1=5000 {print $5<br>number2=10,$4,$2,$1}' cars.txt | tee awk-5.txt</span><br><br>You can test conditions by issuing # Issue the following linux pipeline command to display the '''Linux commands / pipeline commandscar make''' ,<ubr>or</u><br>by using the '''testyear''' and '''quantity''' of cars that '''begin''' command. We will demonstrate using with the '''testletter 'f'' command in this tutorial,'':<br>and then we will demonstrate how to test by issuing a <span style="color:blue;font-weight:bold;font-family:courier;">awk ''Linux command $1 ~ /^f/ pipeline command'' in a <u>later{print $1,$2,$4}' cars.txt | tee awk-6.txt</uspan> tutorial.<br><br># Issue the following Linux command to test a condition[[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><span style="color:blue;font-weight:bold;font-family:courier;">test $course = "ULI101"</span>by using '''compound operator''' symbols:<br><br>The '''$?&&''' variable is used to store an '''exit status''' of the <u>previously-issued</u> command &nbsp;&nbsp;&nbsp;&nbsp;(including the test commandand).<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.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(or)<br><br># Issue the following Linux linux pipeline command to view the list all '''exit statusfords''' of the previously-issued <br>whose '''testprice is greater than $10,000''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo awk '$?<1 ~ /ford/span><br&& $5 >10000 {print $0}' cars.txt | tee awk-7.txt<br/span>Based on the ''exit status'' value, is the result ''TRUE'' or ''FALSE''?<br><br># Issue the following Linux linux command to test another condition('''copy and paste''' to save time):<br><span style="color:blue;font-weight:bold;font-family:courier;">test $course = "wget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101"/cars2.txt</nowiki></span><br><br># Issue the following Linux command to view the ''exit status'cat'' ' command to quickly view the contents of the previously-issued '''testcars2.txt''' command:file.<br><span style="color:blue;font-weight:bold;font-family:courier;"br>echo $?</span><br><br>Based on # Issue the following linux pipeline command to display the ''exit status'year''' value, is the result TRUE or FALSE?<br>The value is non-zero (FALSE) since UPPERCASE characters<br>are different than lowercase charactersand '''quantity''' of cars that '''begin''' with the '''letter 'f'''' for the '''cars2.txt''' database:<br><br># Issue the following Linux command to test another condition:<br><span style="colorspan style="color:blue;font-weight:bold;font-family:courier;">test awk '$course != "uli101"1 ~ /^f/ {print $2,$4}' cars2.txt | tee awk-8.txt</span><br><br># Issue a linux command to display the value of '''$What did you notice?'''<br><br>What The problem is that the result? Why?<br><br># Issue the following Linux command to test '''cars2.txt''' database separates each field by a condition involving earlier assigned variables:semi-colon (''';''') <bru>instead<span style="color:blue;font-weight:bold;font-family:courier;">test $number1 > $number2/u> of '''TAB'''.</spanbr>Therefore, it does not recognize the second and fourth fields.<br><br># Issue You need to issue awk with the -F option to indicate that this file's fields are separated (delimited) by a Linux semi-colorn.<br><br># Issue the following linux pipeline command to display the value of '''$?year'''<br><br>and '''NOTE:quantity''' You will notice of cars that something is '''wrongbegin'''with the ''.<br>The exit status 'letter 'f'$?''' shows a zero (TRUE) value, but for the number 5 is definitely NOT greater than 10.<br>The problem is that the symbols '''&lt;cars2.txt''' and '''&gt;''' are interpreted as REDIRECTION symbols!<br><br># To prove this, issue the following Linux command database:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls awk -l 10<F";" '$1 ~ /^f/ {print $2,$4}' cars2.txt | tee awk-9.txt</span><br><br>You should What did you notice this time?<br><br># Issue the following to run a file called "'''10'''". The incorrectly issued '''test''' command '''used redirection'''<br>to create an '''empty''' file and assigning the exit status variable a ''TRUE'' value!<br><br>To prevent problems when issuing the '''test''' command when comparing numbers,<br>you can use the following '''test 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><br>You should notice that the exit status value is now ''FALSE'' which is the correct result.<br><br># The '''test''' command can be substituted by '''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 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 '''control-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,we will only focus on the '''if''' and '''if-else''' logic statements.<br><br># Use a text editor like vi or nano to create the text file called '''if-1.bash'''<br>(eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-1.bash</span>)<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<br>(eg. with vi: press '''ESC''', then type ''':x''' 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:<br><span style="color:blue;font-weight:bold;font-family:courier;">./if-1.bash</span><br><br>Confirm that the output indicates a correct result.<br><br># Use a text editor like vi or nano to create the text file called '''if-2.bash'''<br>(eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-2.bash</span>)<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<br>(eg. with vi: press '''ESC''', then type ''':x''' followed by '''ENTER''').<br><br>[[Image:if-2.png|thumb|right|320px|Output of a shell script using the '''read''' command and 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-2.bash</span><br><br># Run your shell script by issuing:<br><span style="color:blue;font-weight:bold;font-family:courier;">./if-2.bash</span><br><br>When prompted, make certain that the '''first number'''<br>is <u>greater than</u> the '''second number'''. What happens?<br><br># Run the <span style="font-weight:bold;font-family:courier;">./if-2.bash</span> Bash shell script again.<br><br> When prompted, make certain that the '''first number'''<br>is <u>less than or equal to</u> the '''second number'''. What happens?<br><br>Let's use an '''if-else''' statement to provide an '''alternative'''<br>if the first number is less than or equal to the second number.<br><br># Use a text editor like vi or nano to create the text file called '''if-3.bash'''<br>(eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-3.bash</span>)<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>[[Image:if-3.png|thumb|right|330px|Output of a shell script using the '''if-else''' control-flow statement.]]# Save your editing session and exit the text editor<br>(eg. with vi: press '''ESC''', then type ''':x''' 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 if-3.bash</span><br><br># Run your shell script by issuing:<br><span style="color:blue;font-weight:bold;font-family:courier;">./if-3.bash</span><br><br>Try running the script several times with numbers '''different''' and '''equal'''<br>to each other to confirm that the shell script works correctly.<br><br>'''LOOP STATEMENTS''' are a series of steps or sequence of statements executed<br>repeatedly zero or more times satisfying the given condition is satisfied.''<br>Reference: https://www.chegg.com/homework-help/definitions/loop-statement-3<br><br>There are several loops, but we will look at a '''for''' loop using a '''list'''.<br><br># Use a text editor like vi or nano to create the text file called '''for-1.bash'''<br>(eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi for-1.bash</span>)<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<br>(eg. with vi: press '''ESC''', then type ''':x''' 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:<br><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'''<br>(eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi for-2.bash</span>)<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<br>(eg. with vi: press '''ESC''', then type ''':x''' 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:<br><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>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><br># Issue the following Linux command to run a checking scriptchecking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week10week11-check-4 | more2</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>

https://ict.senecacollege.ca/~murray.saul/uli101/uli101_week10_practiceuli101_week11_practice.docx

Note the contents from the following tab-delimited file called '''PART A: WRITE BASH SHELL SCRIPT CODE~murray.saul/uli101/stuff.txt''':(this file pathname exists for checking your work)

'''Write <pre>Line one.This is the answer to each question below second line.This is the question in the space providedthird.This is line four.Five.''' Line six followsFollowed by 7Now line 8and line nineFinally, line 10</pre>

# Write a Bash shell script that clears the screen and displays the text Hello World on the screen.<br><br>What '''permissions''' are required to run this Bash shell script?<br>What are the different methods that you can run this Bash shell script from the command line?<br><br># Write a Bash shell script that clears the screen, prompts the user for their '''full name''' and then prompts results of each of the user following Linux commands for their '''age''', then clears the screen again and welcomes the user by their name and tells them their age.<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># Write a Bash shell script that will first set the value of a read-only variable called '''dogFactor''' to '''7'''. The script will then clear the screen and prompt the user to enter the age of a dog in human years (which will be stored into a variable called '''humanYears''').<br><br>The script will store in a variable called '''dogYears''' the value of ''humanYears x dogFactor''<br>The script will then clear the screen a second time and then display the age of the dog in ''“dog years”''.<br><br># Write a Bash shell script that will clear the screen and then display all '''arguments''' that were entered <u>after</u> your Bash shell script when it was run. Also have the Bash shell script display the '''number of arguments''' that were entered after your Bash shell script.<br><br><br>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 '4 q'Write ~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed '/the expected output from running each of the following Bash shell scripts You can assume that these Bash shell script files have execute permissions/ d' ~murray. Show your worksaul/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>

:'''cat walkthru1.bashPart B: Writing Linux Commands Using the sed Utility'''<pre>#!/usr/bin/bashword1=”counter”word2=”clockwise”echo “The combined word is: $word2$word1”</pre>

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

# Write a Linux sed command to display only lines 5 to 9 for the file:OUTPUT'''~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>

:Note the contents from the following tab-delimited file called '''Walkthru #2:~murray.saul/uli101/stuff.txt''':(this file pathname exists for checking your work)

'''Write the results of each of the following Linux commands for the above-mentioned file:ROUGH WORK:'''

# <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>

:'''cat walkthru2.bashPart D: Writing Linux Commands Using the awk Utility'''<pre>#!/usr/bin/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: '''~/cars''' whose fifth field begins with a number.<br><br># Write a Linux awk command to display the second and third fields for the file: '''~/precars''' 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>