Changes

=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" |Course Notes'''Slides''':<ul><li>Week 11 Lecture 1 Notes:<br> [[Media:ULI101-Week11.1.pdf | PDF]] | [https://ictmatrix.senecacollege.ca/~murraychris.sauljohnson/uli101ULI101/ULI101-Week11.1.pptx PPTX]</li><li>Week 11 Lecture 2 Notes:<br> [[Media:ULI101-Week10Week11.2.pdf | PDF]] | [https://ictmatrix.senecacollege.ca/~murrayjason.saulcarman/uli101slides/ULI101-Week10Week11.2.pptx PPTX]<br></li></ul>

| style="padding-left:15px;" |Shell Scripting'''Text Manipulation:'''* [https://searchdatacenterwww.techtargetdigitalocean.com/definitioncommunity/shelltutorials/the-basics-of-using-the-sed-stream-editor-to-manipulate-text-in-linux Purpose of using the sed utility]* [https://www.digitalocean.com/community/tutorials/how-to-use-the-awk-language-to-manipulate-text-in-script linux Purposeof using the awk utility]

Variables* [https://opensource.com/article/19/8/what| style="padding-are-environment-variables Environment]* [httpsleft://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]15px;" |'''Commands / Techniques* [http://linuxcommand.org/lc3_man_pages/readh.html read]'''* [https://man7.org/linux/man-pages/man1/readonlysed.1p.html readonlysed]* [https://www.gnuman7.org/softwarelinux/bash/manual/html_node/Commandman-Substitution.html Command Substitution]| style="padding-left:15px;"|Control Flow Statements* [https:pages/man1/enawk.wikipedia1p.org/wiki/Control_flow Purpose]* [https://www.computerhope.com/unix/test.htm test command]* [https://ryanstutorials.net/bash-scripting-tutorial/bash-if-statements.php#:~:text=If%20statements%20(and%2C%20closely%20related,conditions%20that%20we%20may%20set. if statement]* [https://www.tutorialspoint.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= <br>In this sectioninvestigation, 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 '''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''' 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 name''checking-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:<br><uspan style="color:blue;font-weight:bold;font-family:courier;">theirsed -n 'p' data.txt | tee sed-1.txt</uspan><br><br> usernameWhat do you notice? You should see only one line. <br><br>You can specify an ''Environment variables'address' make your shell script adaptable by ALL users.'' to display lines using the sed utility<br><br>(eg. ''line # '', 'Save''line #s''' your editing session and or range of '''exitline #s''' the text editor).<br><br>Instead of issuing # Issue the '''bash''' following Linux pipeline command followed by your shell script pathname as an ''argument'',:<br>let<span style="color:blue;font-weight:bold;font-family:courier;">sed -n '1 p's simply run it by its filenamedata. This is the most common method of running shell scriptstxt | tee sed-2.txt</span><br><br>You should see the first line of the text file displayed.<table align="right"br>What other command is used to only display the first line in a file?<tr valign="top"br><tdbr>[[Image:nosed-execute2.png|thumb|right|230px500px|Using the sed command to display a '''range''' of lines.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '2,5 p' data.txt |An tee sed-3.txt</span><br><br>What is displayed? How would you modify the sed command to display the line range 10 to 50?<br><br>The '''error messages''' will appear when trying instruction is used to run '''substitute''' text<br>(a shell script by name that does NOT have similar to method was demonstrated in the vi editor in tutorial 9).<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed '2,5 s/TUTORIAL/LESSON/g' data.txt | tee sed-4.txt | more</span><br><br>What do you notice? View the original contents of lines 2 to 5 in the '''executedata.txt''' permissionsfile<br>in another shell to confirm that the substitution occurred.]]</tdbr><tdbr>[[Image:hello1sed-3.png|thumb|right|150px500px|Output from running your Using the sed command with the '''hello-q''' shell script (YourUserID representing <u>your</u> username)option to display up to a line number, then quit.]]The '''q''' instruction terminates or '''quits''' the execution of the sed utility as soon as it is read in a particular line or matching pattern.</tdbr></tablebr># Issue the following linux Linux pipeline command to run your shell script in your current directory:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed '11 q' data./hellotxt | 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 should notice an can use '''ERROR message'regular expressions'' indicating you don't have permissions to run select lines that match a pattern. In fact,<br>the sed command was one of the file<u>first</u> Linux commands that used regular expression. To fix this, you need to<br><br>The rules remain the same for using regular expressions as demonstrated in '''add execute permissionstutorial 9''' prior to running <br>except the shell scriptregular expression must be contained within '''forward slashes'''<br>(eg. <span style="font-family:courier;font-weight:bold;">/regexp/</span> ).<br><br># Issue [[Image:sed-4.png|thumb|right|400px|Using the following linux sed command to using regular expressions with '''addanchors'''<br>execute permissions for your shell script.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x hellosed -n '/^The/ p' data.txt | tee sed-6.txt</span><br><br>What do you notice?<br><br># Issue the following to run your shell scriptLinux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/d$/ p' data./hellotxt | tee sed-7.txt</span><br><br>Did your shell script runWhat do you notice?<br><br><span style="color:red;">The '''ATTENTION:sed''' Students might get FRUSTRATED when performing their utility can also be used as a '''assignment 3filter''' when their Bash shell scripts have errorsto manipulate text that<br>was generated from Linux commands.<br>One major cause is <br>[[Image:sed-5.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 outputfollowing Linux pipeline command:<br>for the <span style="color:blue;font-weight:bold;font-family:courier;">who | sed -n '/^[a-m]/ p''correct''' Bash shell script| tee sed-8.txt | more</span><br><br>This requires that What did you CAREFULLY notice?<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | sed -n '/txt$/ p''read''' the requirements of your Bash shell script and create it to the EXACT specifications| tee sed-9.txt</span><br><br>What did you notice?<br><br># Issue the following Linux command to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">bash /home/murray.saul~uli101/myscripts/week10week11-check-1</span><br><br># If you encounter errors, make corrections and '''re-run''' the checking script until you<br>until you receive a congratulations message, then you can proceed.<br><br>::In the next investigation, you will learn to create and run shell scripts that<br >use '''variables''', '''positional''' and '''special parameters'''. You will also learn how to<br><u>add</u> a '''she-bang line''' at the top of a shell script to force it to run in a specified shell.<br><br>Proceed to the next investigation.<br><br>

=INVESTIGATION 2: SHE-BANG LINE / VARIABLES / PARAMETERS= In this sectionthe next investigation, you will add a learn how to manipulate text using the '''she-bangawk''' line at the top of your shell script to force the shell script to run in autility.<br>specified shell when executed. You will also learn how to use '''variables''', '''positional''' and '''special parameters'''<br>to make your shell scripts more adaptable.

# Confirm that Change to your '''home''' directory and issue a command to '''confirm'''<br>you are located in your '''home''' directory in your Matrix account.<br><br>Let's run shell scripts # Issue a Linux command to create a directory called '''awk'''<ubr>with</ubr> and # Issue a Linux command to <u>withoutchange</u> a to the '''she-bangawk''' line at directory and confirm you are located in the top of your shell script<br>to demonstrate why using a ''she-bang'awk''' line should be included in a shell script to forcedirectory.<br>the shell script to be run in <br>Let's download a ''specific'' shelldatabase file that contains information regarding classic cars.<br><br># Use a text editor to '''edit''' Issue the following linux command ('''hellocopy and paste''' shell script that you created in the to save time):<ubr>previous</uspan style="color:blue;font-weight:bold;font-family:courier;"> investigation.wget <brnowiki><https://ict.senecacollege.ca/~murray.saul/uli101/cars.txt</nowiki></span><br><br># Add Issue the following line '''cat''' command to quickly view the <u>bottom</u> of contents of the file ('''copycars.txt''' and file.<br><br>The "'''pasteprint''' to prevent ''errors''" action (command):is the <u>default</u> action of awk to print<br><span style="font-family:courier;font-weight:bold;">echo "The current shell you are using is: $(ps -o cmd= -p $$|cut -d' ' -f1)"</span>all selected lines that match a '''pattern'''.<br><br>This '''FYI:action''' This command displays the (contained in braces) can provide more options<br>such as printing '''namespecific fields''' of the ''shell'' that the shell script is running inselected lines (or records) from a database.<br>The command within <span style="font-familybr>[[Image:courier;fontawk-weight:bold;">$( )</span> uses a technique known as '''command substitution'''1.<br><br># Issue png|thumb|right|400px|Using the following Linux awk command to change to an older shell called display matches of the pattern '''Bourne Shellford''':<br><span style=.]]# Issue the following linux command all to display all lines (i.e. records) in the '''cars.txt''' database that matches the pattern (or "make"color:blue;) called '''ford''':<br><span style="color:blue;font-weight:bold;font-family:courier;">shawk '/ford/ {print}' cars.txt</span><br><br>You should notice your We will use '''shell prompt changedpipeline commands''' which indicates<brto both display stdout to the screen and save to files for <u>confirmation</u>that you are of running these pipeline commands when run a '''checking-script''' later in a different shellthis investigation.<br><br>[[Image:hello2.png|thumb|right|275px|Changing # Issue the following linux pipeline command all to display records<br>in the Bourne shell and running shell script '''withoutcars.txt''' a '''She-bangdatabase that contain the pattern (i.e. make) ''' line.]]# Issue the following Linux command to run your shell script in the ford''Bourne Shell'':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '/ford/' cars./hellotxt | tee awk-1.txt</span><br><br>You What do you notice? You should see that you are currently running the shell script "'''sh'''"notice ALL lines displayed <u>without<br/u>which represents the using '''Bourne shellsearch criteria'''.<br><br>You can use ''builtin''NOTE:''' Due to variables''' with the fact that shells (and their features) have '''evolvedprint''' over a period of time,command for further processing.<br>an error may occur if you include a '''NEWER shell feature''' (e.g. ''Bash Shell'') but run it in an '''OLDER shell''' (For example: the ''Bourne Shell'').We will discuss the following variables in this tutorial:<br><br>[[Image:sheawk-bang-12.png|thumb|right|275px400px|Adding a Using the awk command to print search results by '''she-bang linefield number''' at the BEGINNING of the first line in you shell script forces the shell script to be run in that specific shell (in this case, the Bash shell).]]You can add a '''special comment''' called a $0'''she-bang Current record (entire line)<br>''' at the BEGINNING of the $1''' - First field in record<br><u>FIRST line</u> of your shell script to '''force$n''' it to run - nth field in the shell you wantrecord<br>(for example: the Bash shell'''NR''' - Record Number (order in database).<br><br> # Edit your '''helloNF''' shell script using - Number of fields in current record<br><br>For a text editorlisting of more variables, please consult your course notes.<br><br># Issue the following linux pipeline command to display the '''Insertmodel''' the following line at the , '''beginningyear''' of the , '''firstquantity''' line of your hello file:and price<br><span style="font-familyin the '''cars.txt''' database for makes of '''chevy''':<br><span style="color:courierblue;font-weight:bold;font-family:courier;">#!awk '/binchevy/bash<{print $2,$3,$4,$5}' cars.txt | tee awk-2.txt</span><br><br>This is referred to as Notice that a '''she-bang linespace'''is the delimiter for the fields that appear as standard output. It forces this script to be run in the <br><br>The '''tilde character''' '''Bash Shell~'''is used to search for a pattern or display standard output for a particular field.<br>When your Bash Shell script finishes execution, you are returned <br># Issue the following linux pipeline command to your current shell that you are using display all '''plymouths''' (which in our case in Matrix, is still the Bash shell'''plym''').<br><br>[[Image:hello3.png|thumb|right|275px|Changing the Bourne shell and running shell script by '''model name'with'', ' a ''price'She-bang''and ' line (forcing script to run in the ''quantity'Bash''' shell).]]# '''Save''' your editing changes and '''exit''' your text editor.<br:<br><br># While in the ''Bourne shell'', issue the following Linux command:<br><span style="color:span style="color:blue;font-weight:bold;font-family:courier;">.awk '$1 ~ /hello<plym/span><br{print $2,$3,$4,$5}' cars.txt | tee awk-3.txt</span><br><br>You should notice that the shell name is running in the can also use '''Bash shellcomparison operators''' (i.e. ''/bin/bash'').to specify conditions for processing with matched patterns<br>when using the awk command. Since they are used WITHIN the awk expression,<br> It is a good idea to rename your shell script to include an '''extension''' tothey are not confused with redirection symbols<br>indicate that it is a <br>[[Image:awk-3.png|thumb|right|400px|Using the awk command to display results based on '''Bash Shellcomparison operators''' script. ]]'''<br>''' &nbsp;&nbsp;&nbsp;&nbsp;Less than<br># Issue the following Linux command to rename your shell script file:'''<=''' &nbsp;&nbsp;Less than or equal<br><span style="color:blue'''>''' &nbsp;&nbsp;font-weight:bold&nbsp;font-family:courier&nbsp;">mv hello hello.bash</span>Greater than<br><br'''># Confirm that the renamed Bash shell script works by issuing:=''' &nbsp;&nbsp;Greater than or equal<br><span style'''=="color:blue''' &nbsp;font-weight:bold&nbsp;font-family:courierEqual<br>'''!=''' &nbsp;&nbsp;&nbsp;">./hello.bash</span>Not equal<br><br># Enter Issue the following Linux linux pipeline command to display display the '''exitcar make''' the , ''Bourne shell'model' and return to your ''Bash shell, '''quantity''' and '''price''' of all vehicles whose '''prices are less than $5,000''':<br><span style="color:blue;font-weight:bold;font-family:courier;">exitawk '$5 </span><br>5000 {print $1,$2,$4,$5}' cars.txt | tee awk-4.txt</span><br>'''Environment variables''' are used to set the environment of the shell or shell scripts<br>Let's include some '''ENVIRONMENT variables''' in our Bash Shell script.What do you notice?<br><br># Use a text editor Issue the following linux pipeline command to edit the shell script called display display '''hello.bashprice''',<br><br># Add the following lines to the <u>bottom</u> of the ''hello.bash'quantity''', '''model''' and '''car make' file:<br><span style'' of vehicles whose '''prices are less than $5,000''':<br><span style="color:blue;font-familyweight:courierbold;font-weightfamily:boldcourier;">echoawk '$5 < 5000 {print $5,$4,$2,$1}' cars.txt | tee awk-5.txt</span><br>echo "The current directory location is: $PWD"<br>echo "The current user home directory is: $HOME"<br>echo</span># Issue the following linux pipeline command to display the '''car make''',<br>'''year''' and '''quantity''' of cars that '''begin''' with the '''letter 'f'''':<br># Save your editing changes and exit your text editor.<br><br>[[Imagespan style="color:blue;font-weight:hello4bold;font-0.png|thumb|right|330px|Running <ufamily:courier;">modified<awk '$1 ~ /^f/u> {print $1,$2,$4}''hellocars.txt | tee awk-6.bash'' Bash shell script by using relative pathname: txt</span style="font><br><br>[[Image:awk-family:courier;">4.png|thumb|right|400px|Using the awk command to display combined search results based on '''compound operators'./hello.bash''</span>.]]# Run your modified Bash shell script Combined pattern searches can be made<br>by issuingusing '''compound operator''' symbols:<br><span style="color:bluebr>'''&&''' &nbsp;&nbsp;&nbsp;font-weight:bold&nbsp;font-family:courier;">./hello.bash</span>(and)<br><br>Take time to view the output and the values of the environment variables.'''||''' &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(or)<br><br>You can modify # Issue the PATH variable following linux pipeline command to include the current directory (i.e. ".")list all '''fords'''<br>so you can run the command by just script filenamewhose '''price is greater than $10,000''':<br>(eg. <span style="font-familycolor:courierblue;font-weight:bold;">hello.bash</span> as opposed to <span style="fontfont-family:courier;font-weight:bold;">.awk '$1 ~ /hello.bash<ford/span&& $5 >)<10000 {print $0}' cars.txt | tee awk-7.txt</span><br><br># Issue the following Linux linux command to add your current directory to the ('''PATHcopy and paste''' environment variableto save time):<br><span style="color:blue;font-weight:bold;font-family:courier;">PATH=$PATHwget <nowiki>https://ict.senecacollege.<ca/span~murray.saul/uli101/cars2.txt</nowiki><br/span><br>[[Image:hello4.png|thumb|right|330px|Running <u>modified</ubr> # Issue the '''cat'hello.bash'' Bash shell script by entering command to quickly view the contents of the '''cars2.txt''' file.<ubr>just</ubr> # Issue the following linux pipeline command to display the '''filenameyear''' (i.e. <span style="font-family:courier;"br>and ''hello.bash'quantity'</span> and NOT <span style="font-family:courier;">''./hello.bashof cars that ''</span> shown in previous diagram).]]# Issue the following Linux command to confirm that the current directory 'begin''"."'with the ''<br>has been 'letter 'f'added''' to the <u>end</u> of for the '''PATHcars2.txt'''' environment variabledatabase:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo awk '$PATH1 ~ /^f/ {print $2,$4}' cars2.txt | tee awk-8.txt</span><br><br># Issue the following to run your Bash shell script just by name:What did you notice?<br><span style="color:blue;font-weight:bold;font-family:courier;"br>helloThe problem is that the '''cars2.bashtxt''' database separates each field by a semi-colon (''';''') </spanu>instead<br/u>of '''TAB'''.<br>Did your Bash shell script run?Therefore, it does not recognize the second and fourth fields.<br><br># Exit your Matrix session, and log back into your Matrix sessionYou need to issue awk with the -F option to indicate that this file's fields are separated (delimited) by a semi-colorn.<br><br># Re-run Issue the following linux pipeline command to display the '''hello.bashyear''' shell script by just using the name.<br><br>What did you notice?<br><br>The setting of the and '''PATHquantity''' environment variable only worked in the current session onlyof cars that '''begin''' with the '''letter 'f'''' for the '''cars2.txt''' database:<br>If you exit the current Matrix session, then the recently changed settings for environment variables will be lost.<br<span style="color:blue;font-weight:bold;font-family:courier;">You will in a <u>future<awk -F";" '$1 ~ /^f/u> tutorial how to set environment variables in {print $2,$4}'''startcars2.txt | tee awk-up''' files9.txt</span><br><br><span styleWhat did you notice this time?<br><br># Issue the following to run a checking script:<br><span style="color:redblue;">font-weight:bold;font-family:courier;">~uli101/week11-check-2</span><br><br>If you encounter errors, make corrections and '''ATTENTION:re-run''' Students might get FRUSTRATED when performing their '''assignment 3''' when their Bash shell scripts have errors.the checking script until you<br>One major cause is the the OUTPUT of their Bash shell script when run does not '''EXACTLY match''' the required output<br>for the '''correct''' Bash shell script.<br><br>This requires that receive a congratulations message, then you CAREFULLY '''read''' the requirements of your Bash shell script and create it to the EXACT specifications</span>can proceed.<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-2 | 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>Unlike '''Environment variables''' that are used to set the environment of the shell or shell scripts,<br>'''User-created''' variables are "customized" that the user can set or allow a user to set the variables' values.<br>Let's create a Bash shell script that contain '''user-created variables'''.<br><br># Use a text editor to create a Bash shell script called '''user-variables.bash'''<br><br># Add the following lines to the beginning of the ''user-variables.bash'' file:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>read -p "Enter your Full Name: " name<br>read -p "Enter your age (in years): " age<br>echo "Hello $name - You are $age years old"</span><br><br># Save your editing changes and exit your text editor.<br><br>[[Image:user-variable1.png|thumb|right|300px|Prompting user to enter data via the '''read -p''' command storing into '''user-created variable'''.]]# Issue the '''chmod''' command to add '''execute permissions'''<br>for the '''user-variables.bash''' file.<br><br># Issue the following to run the user-variables.bash Bash shell script<br> (enter '''your Full name''' and '''your age''' when prompted):<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>A '''positional parameter''' is a special variable within a shell program; its value is set from '''arguments''' contained in a shell script or using the set command.<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;">./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.<br>

=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=<br>In this section, you will learn how to use '''command substitution''' and '''math operations''' in your shell scripts.

''For example'Review Questions:'''

<span style="font-family'''Part A:courier;font-weight:bold;">echo "The current date and time is: $(date)"</span>Display Results from Using the sed Utility'''

Let's create a Bash shell script that uses command substitution that displays<brpre>'''text''' and values of '''environment variables''' in a series of <span style="font-family:courier;font-weight:bold;">echo</span> statementsLine one.<br><br> '''Perform This is the Following Steps:''' # Confirm that you are located in your '''home''' directory in your Matrix accountsecond line.<br><br># Use a text editor to create a Bash shell script called '''command-substitution.bash'''<br><br># Add the following lines to This is the beginning of this file:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>echo<br>echo "MY ACCOUNT INFORMATION:"<br>echo<br>echo "Username: $(whoami)"<br>echo<br>echo "Current Directory: $(pwd)"<br>echo<br></span><br>[[Image:commandsubstitution1third.png|thumb|right|275px|Output of a shell script using command substitution.]]# Save your editing changes and exit your text editorThis is line four.<br><br># Issue the '''chmod''' command to add execute permissions<br>for the '''command-substitution.bash''' fileFive.<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;">./command-substitution.bash</span><br><br>Confirm that your shell script displays the correct information for your Matrix account.<br><br>Line six followsFollowed by 7'''Math Operations'''Now line 8and line nineSince you do NOT have to declare the '''data-type''' of a variable (as opposed to compiled program<br>such as the C-programming language)Finally, numbers would be stored as '''text''' in variables.<br>Therefore, it is important to use the construct <span style="color:blue;font-family:courier;font-weight:bold">(( ))</span> to <u>convertline 10</upre> numbers (stored as ''text'') into '''numbers'''. We will now learn how to use this construct in order to perform math operations for shell scripts.<br><br>'''Perform the Following Steps:'''

:In Write the results of each of the following Linux commands for the next investigation, you will use '''controlabove-flow statements''' to allow your shell scripts<br>to perform differently under different situations.<br><br>mentioned file:

The purpose of this section is to obtain '''extra practice''' to help with '''quizzes''', your '''midterm''', and your '''final exam'''. Here is Write a link single Linux command to perform the MS Word Document of ALL specified tasks for each of the following questions displayed below but with extra room to answer on the document tosimulate a quiz:.

Your instructor may take-up these questions during class# Write a Linux sed command to display only lines 5 to 9 for the file: '''~murray. It is up saul/uli101/stuff.txt'''<br><br># Write a Linux sed command to display only lines the student begin the pattern “and” for the file: '''~murray.saul/uli101/stuff.txt'''<br><br># Write a Linux sed command to attend classes in order display only lines that end with a digit for the file: '''~murray.saul/uli101/stuff.txt'''<br><br># Write a Linux sed command to obtain save lines that match the answers to pattern “line” (upper or lowercase) for the following questionsfile: '''~murray.saul/uli101/stuff. Your instructor will NOT provide these answers in any other form txt''' and save results (eg. e-mail, etcoverwriting previous contents)to: '''~/results.txt'''<br><br>

'''Review QuestionsPart C:Writing Linux Commands Using the awk Utility'''

'''PART B# <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: WALKbold">awk ‘$1 ~ /This/ {print $2}’ ~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-THRUS'''family:courier;font-weight:bold">awk ‘$1 ~ /This/ {print $3,$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>