=INTRODUCTION TO SHELL SCRIPTINGUSING SED & AWK UTILTIES=
<br>
===Main Objectives of this Practice Tutorial===
:* Understand Use the process for planning prior '''sed''' command to writing '''manipulate text''' contained in a shell scriptfile.
:* Understand List and explain several '''addresses''' and '''instructions''' associated with the purpose of a she-bang line contained at the top of a shell script'''sed''' command.
:* Setting permissions for Use the '''sed''' command as a shell script and properly execute a shell script'''filter''' with Linux pipeline commands.
:* Understand and use environment and user-defined variables within Use the '''awk''' command to '''manipulate text''' contained in a shell scriptfile.
:* Understand List and explain '''comparison operators''', '''variables''' and '''actions''' associated with the purpose of control flow statements used with shell scripts'''awk''' command.
:* Use the test '''awk''' command to test various conditionsas a '''filter''' with Linux pipeline commands. :* Use the if logic statement and the for loop statement within shell scripts.<br><br>
===Tutorial Reference Material===
|- valign="top" style="padding-left:15px;"
|colspan="2" |
Course Notes'''Slides''':<ul><li>
Week 11 Lecture 1 Notes:<br> [[Media:ULI101-Week11.1.pdf | PDF]] | [https://
ictmatrix.senecacollege.ca/~
murraychris.
sauljohnson/
uli101ULI101/ULI101-Week11.1.pptx PPTX]</
li><li>Week 11 Lecture 2 Notes:<br> [[Media:ULI101-
Week10Week11.2.pdf
| PDF
]] | [https://
ictmatrix.senecacollege.ca/~
murrayjason.
saulcarman/
uli101slides/ULI101-
Week10Week11.2.pptx PPTX]
<br></li></ul>
| style="padding-left:15px;" |'''Text Manipulation:'''
* [https://www.digitalocean.com/community/tutorials/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-linux Purpose of using the awk utility]
| style="padding-left:15px;" |Shell Scripting* [https'''Commands://searchdatacenter.techtarget.com/definition/shell-script Purpose]'''* [https://wwwman7.youtube.comorg/watch?v=cQepf9fY6cE Creating and Running a Shell Script]<br>Variables* [https:linux//opensource.com/article/19/8/whatman-are-environment-variables Environment]* [https:pages/man1/wwwsed.linuxtechi.com/variables-in-shell-scripting/#:~:text=User%20Defined%20Variables%3A,like%20a%20real%20computer%20program. User Defined]Commands* [http://linuxcommand.org/lc3_man_pages/readh1p.html readsed]* [https://man7.org/linux/man-pages/man1/readonlyawk.1p.html readonlyawk]
| style="padding-left:15px;"|Control Flow Statements
* [https://en.wikipedia.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.cyberciti.biz/faq/bash-for-loop/#:~:text=A%20'for%20loop'%20is%20a,files%20using%20a%20for%20loop. for loop]
|colspan="1" style="padding-left:15px;" width="30%"|
'''Brauer Instructional Videos:
'''<ul><li>[https://www.youtube.com/watch?v=
kxEP-KUhOSgnpU6S61AIko&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=
5 Introduction to Shell Scripting14 Using the sed Utility]</li><li>[https://www.youtube.com/watch?v=
XVTwbINXnk4OV3XzjDYgJo&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=
6 13 Using
Variables and Control Flow Statements in Shell Scriptingthe awk Utility]</ul>
|}
= KEY CONCEPTS =
A shell script is a computer program designed to be run by the Unix shell, a command-line interpreter.<br> The various dialects of shell scripts are considered to be scripting languages.
Reference: https://en.wikipedia.org/wiki/Shell_script===Using the sed Utility===
===Creating & Executing Shell Scripts===
[[Image:ipso.png|thumb|right|500px|An IPSO Diagram (INPUT, PROCESSING, STORAGE, OUTPUT) can be used to map-out and then list the sequence of steps to assist when coding your shell script.]]It is recommended to '''plan''' out on a piece of paper the purpose of the shell script.<br>You can do this by creating a simple '''IPSO''' diagram (stands for '''INPUT''', '''PROCESSING''', '''STORAGE''', '''OUTPUTUsage:''').
First, list the INPUTS into the script (eg. prompting user for data, reading data from file, etc), then listing the expected OUTPUTS from the script. You can then list the steps to process the INPUT to provide the OUTPUT (including file storage).'''<span style="color:blue;font-weight:bold;font-family:courier;">Syntax: sed [-n] 'address instruction' filename</span>'''
Once you have planned your shell script by listing the sequence of steps in your script, you need to create a file (using a '''text editor''') that will contain your Linux commands.<br>'''NOTE:''' Avoid using filenames of already existing Linux Commands to avoid confusion. Using shell script filenames that include the file extension of the shell that the script will run within is recommended.
'''Using a Shebang LineHow it Works:'''
[[Image:shebang.png|thumb|right|200px|* The '''shebang line''' sed command reads all lines in the input file and will be exposed to the expression<ubr>must</u> appear on the '''first (i.e. area contained within quotes) one line''' at a time.* The expression can be within single quotes or double quotes.* The expression contains an address (match condition) and at the '''beginning''' of the shell scriptan instruction (operation).]]* If you are learning Bash scripting by reading other people’s code you might have noticed<br>that the first line in the scripts starts with the #! characters and the path to the Bash interpretermatches the address, then it will perform the instruction.This sequence of characters (#!) is called * Lines will display be default unless the '''shebang–n''' and option is used to tell the operating systemsuppress default display<br>which interpreter to use to parse the rest of the file. Reference'''Address: https://linuxize.com/post/bash-shebang/'''
The * Can use a line number, to select a specific line (for example: '''shebang line5''' <u>must</u> appear on the )* Can specify a range of line numbers (for example: '''first line5,7''' and at the )* Regular expressions are contained within forward slashes (e.g. /regular-expression/)* Can specify a regular expression to select all lines that match a pattern (e.g '''beginning/^[0-9].*[0-9]$/''' of ) * If NO address is present, the shell script,<br>otherwise, it instruction will be treated as a regular comment and ignored.apply to ALL lines
'''Setting Permissions & Running a Shell Script'''
To run your shell script by name, you need to assign execute permissions for the user.<br>To run the shell script, you can execute it using a relative, absolute, or relative-to-home pathname
'''Example:<br><br><span style="font-family:courier;">chmod u+x myscript.bash<br>./myscript.bash<br>/home/username/myscript.bash<br>~/myscript.bash</span>
'''
===Using Variables in Shell Scripts===
'''Definition'''
'''Variables''' are used to '''store information''' to be referenced and manipulated in a computer program.<br>They also provide a way of labeling data with a descriptive name, so our programs can be understood<br>more clearly by the reader and ourselves.<br>'''Reference:''' https://launchschool.com/books/ruby/read/variables
'''Environment Variables'''
[[Image:environment.png|thumb|right|500px|Examples of using '''Environment''' and '''User Defined''' variables.]]Shell environment variables shape the working environment whenever you are logged in Common shell. Some of these variables are displayed via Linux commands in the diagram displayed on the right-side.<br>(you can issue the pipeline command '''set | more''' to view all variables)
Placing a dollar sign ('''$''') prior to the variable name will cause the variable to expand to the value contained in the variable.
'''User Defined Variables'''
'''User-defined variables''' are variables which can be '''created by the user''' and exist in the session. This means that no one can access user-defined variables that have been set by another user,<br>and when the session is closed these variables expire.<br>'''Reference:''' https://mariadb.com/kb/en/user-defined-variables/
Data can be stored and removed within a variable using an equal sign.<br>The '''read''' command can be used to prompt the user to enter data into a variable.<br>Refer to the diagram on the right-side to see how user-defined variables are assigned data.
'''Positional Parameters and Special Parameters'''
[[Image:positional.png|thumb|right|220px|Examples of using '''positional''' and '''special''' parameters.]]A '''positional parameter''' is a variable within a shell program; its value is set from an argument specified on the command line that invokes the program.
Positional parameters are numbered and are referred to with a preceding "'''$'''": '''$1''', '''$2''', '''$3''', and so on. The positional parameter $0 refers to either the name of shell where command was issued, or name of shell script being executed. If using '''positional parameters''' greater than '''9''', then you need to include number within braces.<br>Examples: '''echo ${10}''', '''ls ${23}'''
The '''shift''' command can be used with positional parameters to shift positional parameters<br>to the left by one or more positions.
There are a few ways to assign values as positional parameters:
:*Use the '''set''' command with the values as argument after the set command
:*Run a shell script containing arguments
[[Image:sed.png|right|500px|]]
'''Instruction:'''
*'''Action''' to take for matched line(s)
*Refer to table on right-side for list of some<br>'''common instructions''' and their purpose
<br><br>
There are a group of '''special parameters''' that can be used for shell scripting.<br>A few of these special parameters and their purpose are displayed below:<br>'''$*''' , '''“$*”''' , '''"$@"''' , '''$#''' , '''$?''' Refer to the diagram to the right for examples using positional and special parameters. ===Using Control Flow Statements in Shell Scriptsthe awk Utility===
<table align="right"><tr valign="top"><td>[[Image:test-1.png|thumb|right|140px|Examples of simple comparisons using the test command.]]</td><td>[[Image:test-2.png|thumb|right|140px|Examples of using additional comparisons using the test command.]]</td></table>
Control Flow Statement are used to make your shell scripts more flexible and can adapt to changing situations.
The special parameter '''$?Usage:''' Is used to determine the exit status of the previously issued Linux command.The exit status will either display a zero (representing TRUE) or a non-zero number (representing FALSE). This can be used to determined if a Linux command was correctly or incorrectly executed.
The <span style="color:blue;font-weight:bold;font-family:courier;">awk [-F] '''test''' Linux command is used to test conditions to see if they are '''TRUE''' (i.e. value '''zero''') or '''FALSE''' (i.e. value '''nonselection-criteria {action}’ file-zero''') so they can be used with control flow statements to control the sequence of a shell script.name</span>
You CANNOT use the '''>''' or '''<''' symbols when using the test command since these are redirection symbols. Instead, you need to use options when performing numerical comparisons.
Refer to the table below for test options and their purposes.
There are <u>other</u> comparison options that can be used with the test command such as testing to see if a regular file or directory pathname exists, or if the regular file pathname is –non-empty.'''How It Works:'''
Refer * The '''awk''' command reads all lines in the input file and will be exposed to diagrams the expression (contained within quotes) for processing.*The '''expression''' (contained in quotes) represents '''selection criteria''', and '''action''' to execute contained within braces '''{}'''* if selection criteria is matched, then action (between braces) is executed.* The '''–F''' option can be used to specify the right involving the test commanddefault '''field delimiter''' (separator) character<br>eg. '''awk –F”;”''' (would indicate a semi-colon delimited input file).<br>'''Selection Criteria'''
* You can use a regular expression, enclosed within slashes, as a pattern. For example: '''Logic Statements/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 ( '''>''' , '''>=''' , '''<''' , '''<=''' , '''==''' , '''!=''' ).* 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: '''NR >=1 && NR <= 5''' <br>'''Action (execution):'''
A * Action to be executed is contained within braces '''{}'''logic statement* The ''' is print''' command can be used to determine display text (fields).* You can use parameters which Linux commands to be executed based<br>on represent fields within records (lines) within the expression of the result awk utility.* The parameter '''$0''' represents all of a condition the fields contained in the record (iline).e* The parameters '''$1''', '''$2''', '''$3''' … '''$9''' represent the first, second and third to the 9th fields contained within the record. TRUE * Parameters greater than nine requires the value of the parameter to be placed within braces (zero valuefor example: '''${10}''','''${11}''','''${12}''', etc.) or FALSE * You can use built-in '''variables''' (non-zero valuesuch as '''NR''' or "record number" representing line number)<br>eg. '''{print NR,$0}''' (will print record number, then entire record).
<table align="right"><tr valign="top"><td>[[Image:logic-INVESTIGATION 1.png|thumb|right|250px|Example of using the '''if''' logic control-flow statement.]]</td><td>[[Image:loop-1.png|thumb|right|250px|Example of using the '''for''' looping control-flow statement.]]</td></table>USING THE SED UTILITY=
There are several logic statements, but we will just concentrate on the if statement.<pre span style="widthcolor:20%red;">if test condition then command(s) fi'''ATTENTION''': Effective '''May 9, 2022''' - this online tutorial will be required to be completed by '''Friday in week 11 by midnight'''<br>to obtain a grade of '''2%''' towards this course</prespan><br><br>
Refer In this investigation, you will learn how to manipulate text using the diagram relating to logic statements on the right side for an example'''sed''' utility.
'''Loop Statements'''
A '''loop statementPerform the Following Steps:''' is a series of steps or sequence of statements executed repeatedly zero or more times satisfying the given condition is satisfied.<br>Reference: https://www.chegg.com/homework-help/definitions/loop-statement-3
There # '''Login''' to your matrix account and confirm you are several loopslocated in your '''home''' directory.<br><br># Issue a Linux command to create a directory called '''sed'''<br><br># Issue a Linux command to <u>change</u> to the '''sed''' directory and confirm that you are located in the '''sed''' directory.<br><br># Issue the following Linux command to download the data.txt file<br>('''copy and paste''' to save time):<br><span style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/data.txt</nowiki></span><br><br># Issue the '''more''' command to quickly view the contents of the '''data.txt''' file.<br>When finished, but we exit the more command by pressing the letter <span style="color:blue;font-weight:bold;font-family:courier;">q</span>[[Image:sed-1.png|thumb|right|300px|Issuing the '''p''' instruction without using the '''-n''' option (to suppress original output) will display lines twice.]]<br><br>The '''p''' instruction with the '''sed''' command is used to<br>'''print''' (i.e. ''display'') the contents of a text file.<br><br># Issue the following Linux command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed 'p' data.txt</span><br><br>'''NOTE: You should notice that each line appears twice'''.<br><br>The reason why standard output appears twice is that the sed command<br>(without the '''-n option''') displays all lines regardless of an address used.<br><br>We will look at use '''pipeline commands''' to both display stdout to the screen and save to files<br>for loop <u>confirmation</u> of running these pipeline commands when run a '''checking-script''' later in this investigation.<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n 'p' data.txt | tee sed-1.txt</span><br><br>What do you notice? You should see only one line.<br><br>You can specify an '''address''' to display lines using the sed utility<br>(eg. ''line #'', '''line #s''' or range of '''line #s''').<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '1 p' data.txt | tee sed-2.txt</span><br><br>You should see the first line of the text file displayed.<br>What other command is used to only display the first line in a file?<br><br>[[Image:sed-2.png|thumb|right|500px|Using the sed command to display a list'''range''' of lines.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '2,5 p' data.txt | tee sed-3.txt</span><br><br>What is displayed? How would you modify the sed command to display the line range 10 to 50?<br><br>The '''s''' instruction is used to '''substitute''' text<br>(a similar to method was demonstrated in the vi editor in tutorial 9).<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed '2,5 s/TUTORIAL/LESSON/g' data.txt | tee sed-4.txt | more</span><br><br>What do you notice? 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><br>[[Image:sed-3.png|thumb|right|500px|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 | tee sed-5.txt</span><br><br>What did you notice? How many lines were displayed<br>before the sed command exited?<br><br>You can use '''regular expressions''' to select lines that match a pattern. In fact,<br>the sed command was one of the <u>first</u> Linux commands that used regular expression.<br><br>The rules remain the same for using regular expressions as demonstrated in '''tutorial 9'''<br>except the regular expression must be contained within '''forward slashes'''<br>(eg. <span style="font-family:courier;font-weight:bold;">/regexp/</span> ).<br><br>[[Image:sed-4.png|thumb|right|400px|Using the sed command using regular expressions with '''anchors'''.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/^The/ p' data.txt | tee sed-6.txt</span><br><br>What do you notice?<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/d$/ p' data.txt | tee sed-7.txt</span><br><br>What do you notice?<br><br>The '''sed''' utility can also be used as a '''filter''' to manipulate text that<br>was generated from Linux commands.<br><br>[[Image:sed-5.png|thumb|right|400px|Using the sed command with '''pipeline''' commands.]]# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">who | sed -n '/^[a-m]/ p' | tee sed-8.txt | more</span><br><br>What did you notice?<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | sed -n '/txt$/ p' | tee sed-9.txt</span><br><br>What did you notice?<br><br># Issue the following to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week11-check-1</span><br><br>If you encounter errors, make corrections and '''re-run''' the checking script<br>until you receive a congratulations message, then you can proceed.<br><br>
:In the next investigation, you will learn how to manipulate text using the '''awk''' utility.<pre style="width:20%"br>for item in list do command(s) done</prebr>
Refer to the diagram relating to looping statements on the right side for an example. =INVESTIGATION 12: CREATING A SHELL SCRIPTUSING THE AWK UTILITY = <br>In this section, you will learn how to create and run a simple Bash Shell script.
In this investigation, you will learn how to use the awk utility to manipulate text and generate reports.
'''Perform the Following Steps:'''
# Change to your '''home''' directory and issue a command to '''Loginconfirm''' <br>you are located in your matrix account''home'' directory.<br><br># Issue a Linux command to create a directory called '''confirmawk'''<br><br># Issue a Linux command to <u>change</u> to the '''awk''' directory and confirm you are located in your home the '''awk''' directory.<br><br>We want Let's download a database file that contains information regarding classic cars.<br><br># Issue the following linux command ('''copy and paste''' to create a Bash Shell script save time):<br><span style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/cars.txt</nowiki></span><br><br># Issue the '''cat''' command to welcome quickly view the contents of the '''cars.txt''' file.<br><br>The "'''print'''" action (command) is the user by their username<u>default</u> action of awk to print<br>all selected lines that match a '''pattern'''. Let<br><br>This '''action'''s first (contained in braces) can provide some useful tips more options<br>such as printing '''specific fields''' of selected lines (or records) from a database.<br><br>[[Image:awk-1.png|thumb|right|400px|Using the awk command to display matches of the pattern '''ford'''.]]# Issue the following linux command all to display all lines (i.e. records) in termsthe '''cars.txt''' database that matches the pattern (or "make") called '''ford''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '/ford/ {print}' cars.txt</span><br><br>We will use '''pipeline commands''' to both display stdout to the screen and save to files for <u>confirmation</u>of selecting an appropriate name for the shell running these pipeline commands when run a '''checking-script''' later in this investigation.<br><br># Issue the following linux pipeline command all to check if your intended shell script namedisplay records<br>is already exists to be run automatically from in the '''cars.txt''' database that contain the Bash shellpattern (i.e. make) '''ford''':<br><span style="color:blue;font-weight:bold;font-family:courier;">which helloawk '/ford/' cars.txt | tee awk-1.txt</span><br><br>What do you notice? You should notice that there is no output and therefore, this shell script name ALL lines displayed <u>without</u> using '''search criteria'''.<br><br>You can be useduse ''builtin'' '''variables''' with the '''print''' command for further processing.<br>On We will discuss the other handfollowing variables in this tutorial:<br><br>[[Image:awk-2.png|thumb|right|400px|Using the awk command to print search results by '''field number'''.]]'''$0''' - Current record (entire line)<br>'''$1''' - First field in record<br>'''$n''' - nth field in record<br>'''NR''' - Record Number (order in database)<br> '''NF''' - Number of fields in current record<br><br>For a listing of more variables, if you wanted please consult your course notes.<br><br># Issue the following linux pipeline command to create a file called seddisplay the '''model''', '''year''', then '''quantity''' and price<br>in the '''which sedcars.txt''' database for makes of '''chevy''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '/chevy/ {print $2,$3,$4,$5}' commandcars.txt | tee awk-2.txt</span><br><br>would indicate it Notice that a '''space''' is already being used by the shell and delimiter for the fields that appear as standard output.<br><br>The '''tilde character''''sed''~' wouldn't be an appropriate shell script name ' is used to usesearch for a pattern or display standard output for a particular field.<br><br># Use a text editor like vi or nano Issue the following linux pipeline command to create the text file called hello display all '''plymouths''' (eg. '''plym''')<br>by '''model name''', '''price''' and '''quantity''':<br><span style="color:blue;font-weight:bold;font-family:courier;">vi helloawk '$1 ~ /plym/ {print $2,$3,$4,$5}' cars.txt | tee awk-3.txt</span>)<br><br>If you You can also use '''comparison operators''' to specify conditions for processing with matched patterns<br>when using the awk command. Since they are using used WITHIN the nano text editorawk expression, refer <br>they are not confused with redirection symbols<br><br>[[Image:awk-3.png|thumb|right|400px|Using the awk command to notes display results based on text editing in a previous week in the course schedule'''comparison operators'''.]]'''<''' Less than<br>'''<=''' Less than or equal<br>'''>''' Greater than<br>'''>=''' Greater than or equal<br>'''==''' Equal<br>'''!=''' Not equal<br><br># Enter Issue the following two lines in your shell scriptlinux pipeline command to display display the '''car make''', '''model''', '''quantity''' and '''price''' of all vehicles whose '''prices are less than $5, replacing "your-username" with your actual name000''':<br><span style="color:blue;font-weight:bold;font-family:courier;">clearawk '$5 <br>echo "Hello your5000 {print $1,$2,$4,$5}' cars.txt | tee awk-username"4.txt</span><br><br>What do you notice?<br><br># Save your editing session and exit Issue the text editor (eg. with vi: press following linux pipeline command to display display '''price''',<br>'''ESCquantity''', then type ''':wxmodel''' and '''car make'''of vehicles whose '' followed by 'prices are less than $5,000''ENTER':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$5 < 5000 {print $5,$4,$2,$1}')cars.txt | tee awk-5.txt</span><br><br># Issue the following linux pipeline command to run your shell script in your current directorydisplay the '''car make''',<br>'''year''' and '''quantity''' of cars that '''begin''' with the '''letter 'f'''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$1 ~ /^f/ {print $1,$2,$4}' cars.txt | tee awk-6./hellotxt</span><br><br>You should notice an error indicating you don[[Image:awk-4.png|thumb|right|400px|Using the awk command to display combined search results based on '''compound operators'''t have permissions to run the file.]]Combined pattern searches can be made<br>by using '''compound operator''' symbols:<br><br>'''&&''' (and)<br>You need to first add execute permissions prior to running the shell script.'''||''' (or)<br><br># Issue the following linux pipeline command to add execute permissions for your shell scriptlist all '''fords'''<br>whose '''price is greater than $10,000''':<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x helloawk '$1 ~ /ford/ && $5 > 10000 {print $0}' cars.txt | tee awk-7.txt</span><br><br># Re-run your shell scriptIssue the following linux command ('''copy and paste''' to save time): <br><span style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https://ict.senecacollege.ca/~murray.saul/hellouli101/cars2.txt</nowiki></span><br><br>Although your shell script should work, it is recommended # Issue the '''cat''' command to force your shell script to run in a specific shell. This helps prevent your shell script encountering errors when run in quickly view the contents of the incorrect shell (i'''cars2.e. syntax not recognized in a specific shell)txt''' file.<br><br># Edit your Issue the following linux pipeline command to display the '''helloyear''' shell script using a text editor.<br><br># Insert the following line at and '''quantity''' of cars that '''begin''' with the '''beginningletter 'f'''' of for the '''firstcars2.txt''' line of your hello filedatabase:<br><span style="color:blue;font-weight:bold;font-family:courier;">#!awk '$1 ~ /bin^f/bash{print $2,$4}' cars2.txt | tee awk-8.txt</span><br><br>This What did you notice?<br><br>The problem is referred to as that the '''cars2.txt''' database separates each field by a shesemi-bang line. It forces the script to be run in the Bash Shell. When your Bash Shell script finishes execution, you are returned to your current shell that you are using colon (which in our case in Matrix, is still the Bash shell''';''').<bru>instead</u>of '''TAB'''.<br># Save your editing changes Therefore, it does not recognize the second and exit your text editorfourth fields.<br><br># It is a good idea You need to rename your shell script to include an extension issue awk with the -F option to indicate that the this file is 's fields are separated (delimited) by a Bash Shell script filesemi-colorn. <br><br># Issue the following linux pipeline command to rename your shell script filedisplay the '''year'''<br>and '''quantity''' of cars that '''begin''' with the '''letter 'f'''' for the '''cars2.txt''' database:<br><span style="color:blue;font-weight:bold;font-family:courier;">mv hello helloawk -F";" '$1 ~ /^f/ {print $2,$4}' cars2.txt | tee awk-9.bashtxt</span><br><br>What did you notice this time?<br><br># Run your renamed shell Issue the following to run a checking script by issuing:<br><span style="color:blue;font-weight:bold;font-family:courier;">.~uli101/hello.bashweek11-check-2</span><br><br>If you encounter errors, make corrections and '''re-run''' the checking script until you<br>receive a congratulations message, then you can proceed.<br><br>
::In the next investigation, you will learn to create and run shell scripts that<br>use variables, positional and special parameters.<br><br>= LINUX PRACTICE QUESTIONS =
=INVESTIGATION 2: USING VARIABLES IN SHELL SCRIPTS =The purpose of this section is to obtain '''extra practice''' to help with '''quizzes''', your '''midterm''', and your '''final exam'''.
In this section, you will learn how Here is a link to use variables, positional and special parameters the MS Word Document of ALL of the questions displayed below but with extra room to assist you in creating adaptable shell scripts.answer on the document tosimulate a quiz:
https://ict.senecacollege.ca/~murray.saul/uli101/uli101_week11_practice.docx
Your instructor may take-up these questions during class. It is up to the student to attend classes in order to obtain the answers to the following questions. Your instructor will NOT provide these answers in any other form (eg. e-mail, etc).
'''Perform the Following Steps:'''
# Use a text editor to edit the shell script called '''hello.bash'''<br><br># Add the following line to the bottom of the file:<br><span style="font-family:courier;">echo "The current shell you are using is: $SHELL"</span><br><br># Save your editing changes and exit your text editor.<br><br># Issue the following linux command to change to the Bourne Shell (a different shell than the default Bash):<br><span style="color:blue;font-weight:bold;font-family:courier;">sh</span># Issue the following linux command to confirm you are in the Bourne Shell:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $SHELL</span><br><br>You should see the output of the command that you are located in the Bourne Shell.<br><br># Run your '''hello.bash''' shell script.<br><br>What shell does the shell script indicate is running?<br><br>This is because of the shebang line indicating to run the shell script in the Bash shell although you ran this script within the Bourne Shell.<br><br># Enter the following linux command to return to your Bash shell: <span style="color:blue;font-weight:bold;font-familyReview Questions:courier;">exit</span><br><br># Use a text editor to edit the shell script called '''hello.bash'''<br><br># Add the following lines to the bottom of the file:<br><span style="font-family:courier;">echo "The current username is: $USER"<br>echo "The current directory location is: $PWD"<br>echo "The current user's home directory is: $HOME</span><br><br># Save your editing changes and exit your text editor.<br><br># Run your '''hello.bash''' shell script.<br><br>Take time to view the output and the values of the environment variables.<br><br># Issue the following linux command to add your current directory to the PATH environment variable:<br><span style="color:blue;font-weight:bold;font-family:courier;">PATH=$PATH:.</span><br><br># Issue the following linux command to confirm that the current directory "." has been added to the PATH environment variable:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $PATH</span><br><br># Run the '''hello.bash''' by just shell script name (i.e. to not use ./ prior to shell script name).<br><br>The shell script should run just by name.<br><br># Exit your Matrix session, and log back into your Matrix session.<br><br># Re-run the '''hello.bash''' shell script by just using the name.<br><br>What did you notice?<br><br>The setting of the PATH variable only worked in the current session only. If exit the current Matrix session, then the recently changed settings for environment variables are lost. You will learned in Week 12 how to set environment variables in startup files.<br><br># Use a text editor to create a file called '''user-variables.bash'''<br><br># Add the following lines to the bottom of the file:<br><span style="font-family:courier;">#!/bin/bash<br>age=25<br>readonly age<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># Issue the '''chmod''' command to add execute permissions for the user for the '''user-variables.bash''' file.<br><br># Issue the following to run the user-variables.bash Bash shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">./user-variables.bash</span><br><br>What do you notice when you try to change the age variable? Why?<br><br># Use a text editor to create a file called '''parameters.bash'''<br><br># Add the following lines to the bottom of the file:<br><span style="font-family:courier;">#!/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># Issue the '''chmod''' command to add execute permissions for the user for the '''parameters.bash''' file.<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;">./parameters.bash</span><br><br>What happened?<br><br>The values for the parameters may not be displayed properly since you did NOT provide any arguments when running the 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>Take some time to view the results and how the parameters are changed when using the shift command. What do you notice?
'''Part A: Display Results from Using the sed Utility'''
In Note the next investigation, you will use controlcontents from the following tab-flow statements to allow delimited file called '''~murray.saul/uli101/stuff.txt''':(this file pathname exists for checking your shell scripts to perform differently under different situations.work)
=INVESTIGATION 3: USING CONTROL FLOW STATEMENTS IN SHELL SCRIPTS =<pre>Line one.This is the second line.This is the third.This is line four.Five.Line six followsFollowed by 7Now line 8and line nineFinally, line 10</pre>
In this section, you will learn how to use control-flow statements to make your shell script behave differently under different situation.
Write the results of each of the following Linux commands for the above-mentioned file:
# <span style="font-family:courier;font-weight:bold">sed -n '3,6 p'~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed '4 q'Perform ~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed '/the Following Steps/ d' ~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed 's/line/NUMBER/g''~murray.saul/uli101/stuff.txt</span>
: Before learning about logic and loop control-flow statements, you need to first learn about issuing test conditions using the '''testPart B: Writing Linux Commands Using the sed Utility''' command.
Write a single Linux command to perform the specified tasks for each of the following questions.
# Issue the following linux commands to assign values to several variables:<br><span style="color:blue;font-weight:bold;font-family:courier;">course="ULI101"<br>number1=5<br>number2=10</span><br><br>
# Issue the following linux command to test a condition:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $course = "ULI101"</span><br><br>The '''$?''' variable is used to store an exit status of the previously command issued (including the test command). If the status is zero, then it indicates a TRUE value and if the status is non-zero, then it indicates a FALSE value.<br><br>
# Issue the following linux command to view the status of the previously-issued '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $?</span><br><br>Based on its value, is the result TRUE or FALSE?<br><br>
# Issue the following linux command to test another condition:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $course = "uli101"</span><br><br>
# Issue the following linux command to view the status of the previously-issued '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $?</span><br><br>The value is non-zero (FALSE) since UPPERCASE characters are different than lowercase characters.<br><br>
# Issue the following linux command to test another condition:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $course != "uli101"</span><br><br>
# Issue a linux command to display the value of '''$?'''. What is the result? Why?<br><br>
# Issue the following linux command to test a condition involving numbers:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $number1 > $number2</span><br><br>
# Issue a linux command to display the value of '''$?'''. '''NOTE:''' You will notice that something is '''wrong'''.<br>The exit status '''$?''' shows a zero (TRUE) value, but the number 5 is definitely NOT greater than 10.<br>The problem is that the symbols '''<''' and '''>''' are interpreted as REDIRECTION symbols!<br><br>
# To prove this, issue the following linux command :<br><span style="color:blue;font-weight:bold;font-family:courier;">ls 5</span><br><br>You should notice a file called "'''5'''". The incorrectly issued '''test''' command used redirect to create an empty file instead,<br> which indeed succeeded just giving a TRUE value!<br><br>To prevent these incorrectly issued testing for number comparison, you can use the following options instead:<br>'''-lt''' (<), '''-le''' (<=), '''-gt''' (>), '''-ge''' (>=;), '''-eq''' (=), '''-ne''' (!=)<br><br>
# x
= LINUX PRACTICE QUESTIONS =# Write a Linux sed command to display only lines 5 to 9 for the file: '''~murray.saul/uli101/stuff.txt'''<br><br># Write a Linux sed command to display only lines the begin the pattern “and” for the file: '''~murray.saul/uli101/stuff.txt'''<br><br># Write a Linux sed command to display only lines that end with a digit for the file: '''~murray.saul/uli101/stuff.txt'''<br><br># Write a Linux sed command to save lines that match the pattern “line” (upper or lowercase) for the file: '''~murray.saul/uli101/stuff.txt''' and save results (overwriting previous contents) to: '''~/results.txt'''<br><br>
The purpose of this section is to obtain '''extra practice''' to help with '''quizzes''', your '''midterm''', and your '''final exam'''.
Here is a link to the MS Word Document of ALL of the questions displayed below but with extra room to answer on '''Part C: Writing Linux Commands Using the document tosimulate a quiz:awk Utility'''
https://ict.senecacollege.ca/Note the contents from the following tab-delimited file called '''~murray.saul/uli101/uli101_week10_practice.docx Your instructor may take-up these questions during class. It is up to the student to attend classes in order to obtain the answers to the following questions. Your instructor will NOT provide these answers in any other form (eg. e-mail, etc)stuff. txt'''Review Questions:'''(this file pathname exists for checking your work)
<pre>
Line one.
This is the second line.
This is the third.
This is line four.
Five.
Line six follows
Followed by 7
Now line 8
and line nine
Finally, line 10
</pre>
'''PART A: WRITE BASH SHELL SCRIPT CODE'''
'''Write the answer to results of each question below of the question in following Linux commands for the space provided.above-mentioned file:'''
# Write a Bash shell script that clears the screen and displays the text Hello World on the screen.<brspan style="font-family:courier;font-weight:bold">awk ‘NR == 3 {print}’ ~murray.saul/uli101/stuff.txt<br>What permissions are required to run this Bash shell script?<br><br/span>What are the different ways 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 the user for their '''age''',<brspan style="font-family:courier;font-weight:bold">then clears the screen again and welcomes the user by their name and tells them their age.<brawk ‘NR >= 2 && NR <br>What comments would you add to the above script’s contents to properly document this Bash shell script to be understood= 5 {print}’ ~murray.saul/uli101/stuff.txt<br/span>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 variable called '''number''' to '''23''' and make this variable '''read<span style="font-only'''family:courier;font-weight:bold">awk ‘$1 ~ /This/ {print $2}’ ~murray.<br>Then the script will clear the screen and prompt the user to enter a value for that variable called number to another valuesaul/uli101/stuff.txt<br/span>Have the script display the value of the variable called number to prove that it is a read-only variable.<br><br>When you ran this Bash shell script, did you encounter an error message?# <brspan style="font-family:courier;font-weight:bold">How would you run this Bash shell scriptawk ‘$1 ~ /This/ {print $3, so the error message was NOT displayed?<br><br># Write a Bash shell script that will clear the screen and then display all arguments that were entered after your Bash shell script when it was run$2}’ ~murray. Also have the Bash shell script display the number of arguments that were entered after your Bash shell scriptsaul/uli101/stuff.txt<br/span><br><br>
'''PART B: WALK-THRUS'''
'''Write Part D: Writing Linux Commands Using the expected output from running each of the following Bash shell scripts You can assume that these Bash shell script files have execute permissions. Show your work.awk Utility'''
:'''Walkthru #1:'''
:'''cat walkthru1Write a single Linux command to perform the specified tasks for each of the following questions.bash'''<pre>#!/usr/bin/bashword1=”counter”word2=”clockwise”echo “The combined word is: $word2$word1”</pre>
:WRITE OUTPUT FROM ISSUING:
:'''./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: '''~/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: '''~/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>
:'''Walkthru #2:'''
:'''cat walkthru2.bash'''
<pre>
#!/usr/bin/bash
echo “result1: $1”
echo “result2: $2”
echo “result3: $3”
echo “result 4:”
echo “$*”
</pre>
:WRITE OUTPUT FROM ISSUING:
:'''./walkthru2.bash apple orange banana'''
<br><br>
[[Category:ULI101]]
