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=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'''Commands:'''* [https://searchdatacenter.techtargetman7.comorg/definitionlinux/shellman-script Purpose]* [https:pages/man1/wwwsed.youtube1p.com/watch?v=cQepf9fY6cE Creating and Running a Shell Scripthtml sed]<br>Variables* [https://opensourceman7.comorg/articlelinux/19/8/what-are-environmentman-variables Environment]* [https:pages/man1/www.linuxtechiawk.com/variables-in-shell-scripting/#:~:text=User%20Defined%20Variables%3A,like%20a%20real%20computer%20program1p. User Definedhtml 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 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 =
'''Using a Shebang LineHow it Works:'''
[[Image:sed.png|right|500px|]]'''VariablesInstruction:''' are used to *'''store informationAction''' to be referenced and manipulated in a computer program.<br>They also provide a way take for matched line(s)*Refer to table on right-side for list of labeling data with a descriptive name, so our programs can be understood<br>more clearly by the reader and ourselves.some<br>'''Reference:common instructions''' https://launchschool.com/books/ruby/read/variablesand their purpose<br><br>
* 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]/'''A * The '''!~''' operator tests for no match. For example: '''$2 !~ /line/'''* You can perform both numeric and string comparisons using relational operators ( '''>''' , '''logic statement>=''' , ''' is used to determine which Linux commands to be executed based<br>on ''' , '''<=''' , '''==''' , '''!=''' ).* You can combine any of the patterns using the result of a condition Boolean operators '''||''' (OR) and '''&&''' (iAND).e. TRUE * You can use built-in variables (zero valuelike NR or "record number" representing line number) or FALSE with comparison operators.<br>For example: '''NR >=1 && NR <= 5''' <br>'''Action (non-zero valueexecution)).:'''
'''Perform the Following Steps:'''
# '''Login''' to your matrix accountand confirm you are located in your '''home''' directory.<br><br># Issue a Linux command to create a directory called '''confirmsed'''<br><br># Issue a Linux command to <u>change</u> to the '''sed''' directory and confirm that you are located in your home the '''sed''' directory.<br><br>We want # Issue the following Linux command to create a Bash Shell script to welcome download the user by their usernamedata. Lettxt file<br>('''s first provide some useful tips in termscopy and paste''' to save time):<br>of selecting an appropriate name for the shell script<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 following linux '''more''' command to quickly view the contents of the '''data.txt''' file.<br>When finished, exit the more command by pressing the letter <span style="color:blue;font-weight:bold;font-family:courier;">q</span>[[Image:sed-1.png|thumb|right|300px|Issuing the '''p''' instruction without using the '''-n''' option (to check if your intended shell script namesuppress original output) will display lines twice.]]<br><br>The '''p''' instruction with the '''sed''' command is already exists used to be run automatically from <br>'''print''' (i.e. ''display'') the contents of a text file.<br><br># Issue the Bash shellfollowing Linux command:<br><span style="color:blue;font-weight:bold;font-family:courier;">which hellosed 'p' data.txt</span><br><br>'''NOTE: You should notice that there is no output and therefore, this shell script name can be usedeach line appears twice'''.<br>On <br>The reason why standard output appears twice is that the other hand, if you wanted to create a file called sed, then command<br>(without the '''which sed-n option''' command) displays all lines regardless of an address used.<br><br>would indicate it is already being used by We will use '''pipeline commands''' to both display stdout to the shell screen and that save to files<br>for <u>confirmation</u> of running these pipeline commands when run a '''sedchecking-script''' wouldn't be an appropriate shell script name to uselater in this investigation.<br><br># Use a text editor like vi or nano 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 create display lines using the text file called hello 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;">vi hellosed -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 '''range''' of lines.]]# Enter Issue the following two lines in your shell script, replacing "your-username" with your actual nameLinux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">clearsed -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>echo 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="Hello yourcolor:blue;font-weight:bold;font-usernamefamily:courier;">sed '2,5 s/TUTORIAL/LESSON/g' data.txt | tee sed-4.txt | more</span><br><br># Save your editing session and exit 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 text editor (egsubstitution occurred.<br><br>[[Image:sed-3. png|thumb|right|500px|Using the sed command with vi: press the '''ESC-q'''option to display up to a line number, then type quit.]]The ''':wxq''' followed by instruction terminates or '''ENTERquits''')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 Linux pipeline command to run your shell script in your current directory:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed '11 q' data.txt | tee sed-5./hellotxt</span><br><br>What did you notice? How many lines were displayed<br>before the sed command exited?<br><br>You should notice an error indicating you doncan use '''regular expressions'''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.<br>You need to first add execute permissions prior to running <br>The rules remain the same for using regular expressions as demonstrated in '''tutorial 9'''<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>[[Image:sed-4.png|thumb|right|400px|Using the sed command using regular expressions with '''anchors'''.]]# Issue the following linux Linux pipeline command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x hellosed -n '/^The/ p' data.txt | tee sed-6.txt</span><br><br>What do you notice?<br><br># Re-run your shell scriptIssue the following Linux pipeline command: <br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/d$/ p' data./hellotxt | tee sed-7.txt</span><br><br>You should now see your screen clear and displays What do you notice?<br><br>The '''sed''' utility can also be used as a greeting '''filter''' to you using your usernamemanipulate text that<br>was generated from Linux commands.<br><br>[[Image:sed-5.png|thumb|right|400px|Using the sed command with '''pipeline''' commands.]]# x 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:In the next investigationcourier;">~uli101/week11-check-1</span><br><br>If you encounter errors, you will learn to create make corrections and '''re-run shell scripts that''' the checking script<br>use variablesuntil you receive a congratulations message, positional and special parametersthen you can proceed.<br><br> =INVESTIGATION 2: USING VARIABLES IN SHELL SCRIPTS =
:In this sectionthe next investigation, you will learn how to manipulate text using the '''awk''' utility...<br><br>
=INVESTIGATION 2: USING THE AWK UTILITY =
In this investigation, you will learn how to use the awk utility to manipulate text and generate reports.
'''Perform the Following Steps:'''
# xChange to your '''home''' directory and issue a command to '''confirm'''<br>you are located in your ''home'' directory.<br><br># Issue a Linux command to create a directory called '''awk'''<br><br># Issue a Linux command to <u>change</u> to the '''awk''' directory and confirm you are located in the '''awk''' directory.<br><br>Let's download a database file that contains information regarding classic cars.<br><br># Issue 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/uli101/cars.txt</nowiki></span><br><br># Issue the '''cat''' command to quickly view the contents of the '''cars.txt''' file.<br><br>The "'''print'''" action (command) is the <u>default</u> action of awk to print<br>all selected lines that match a '''pattern'''.<br><br>This '''action''' (contained in braces) can provide 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 the '''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 running these pipeline commands when run a '''checking-script''' later in this investigation.<br><br># Issue the following linux pipeline command all to display records<br>in the '''cars.txt''' database that contain the pattern (i.e. make) '''ford''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '/ford/' cars.txt | tee awk-1.txt</span><br><br>What do you notice? You should notice ALL lines displayed <u>without</u> using '''search criteria'''.<br><br>You can use ''builtin'' '''variables''' with the '''print''' command for further processing.<br>We will discuss the following variables in this tutorial:<br><br>[[Image:awk-2.png|thumb|right|400px|Using the awk command to print search results by '''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, please consult your course notes.<br><br># Issue the following linux pipeline command to display the '''model''', '''year''', '''quantity''' and price<br>in the '''cars.txt''' database for makes of '''chevy''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '/chevy/ {print $2,$3,$4,$5}' cars.txt | tee awk-2.txt</span><br><br>Notice that a '''space''' is the delimiter for the fields that appear as standard output.<br><br>The '''tilde character''' '''~''' is used to search for a pattern or display standard output for a particular field.<br><br># Issue the following linux pipeline command to display all '''plymouths''' ('''plym''')<br>by '''model name''', '''price''' and '''quantity''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$1 ~ /plym/ {print $2,$3,$4,$5}' cars.txt | tee awk-3.txt</span><br><br>You can also use '''comparison operators''' to specify conditions for processing with matched patterns<br>when using the awk command. Since they are used WITHIN the awk expression,<br>they are not confused with redirection symbols<br><br>[[Image:awk-3.png|thumb|right|400px|Using the awk command to display results based on '''comparison operators'''.]]'''<''' Less than<br>'''<=''' Less than or equal<br>'''>''' Greater than<br>'''>=''' Greater than or equal<br>'''==''' Equal<br>'''!=''' Not equal<br><br># Issue the following linux pipeline command to display display the '''car make''', '''model''', '''quantity''' and '''price''' of all vehicles whose '''prices are less than $5,000''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$5 < 5000 {print $1,$2,$4,$5}' cars.txt | tee awk-4.txt</span><br><br>What do you notice?<br><br># Issue the following linux pipeline command to display display '''price''',<br>'''quantity''', '''model''' and '''car make''' of vehicles whose '''prices are less than $5,000''':<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 display 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.txt</span><br><br>[[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>by using '''compound operator''' symbols:<br><br>'''&&''' (and)<br>'''||''' (or)<br><br># Issue the following linux pipeline command to list all '''fords'''<br>whose '''price is greater than $10,000''':<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '$1 ~ /ford/ && $5 > 10000 {print $0}' cars.txt | tee awk-7.txt</span><br><br># Issue 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/uli101/cars2.txt</nowiki></span><br><br># Issue the '''cat''' command to quickly view the contents of the '''cars2.txt''' file.<br><br># Issue the following linux pipeline command to display 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;">awk '$1 ~ /^f/ {print $2,$4}' cars2.txt | tee awk-8.txt</span><br><br>What did you notice?<br><br>The problem is that the '''cars2.txt''' database separates each field by a semi-colon (''';''') <u>instead</u> of '''TAB'''.<br>Therefore, it does not recognize the second and fourth fields.<br><br>You need to issue awk with the -F option to indicate that this file's fields are separated (delimited) by a semi-colorn.<br><br># Issue the following linux pipeline command to display 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;">awk -F";" '$1 ~ /^f/ {print $2,$4}' cars2.txt | tee awk-9.txt</span><br><br>What did you notice this time?<br><br># Issue the following to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week11-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>
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).
# <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 'Review Questions4 q' ~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed '/the/ d'~murray.saul/uli101/stuff.txt</span><br><br># <span style="font-family:courier;font-weight:bold">sed 's/line/NUMBER/g'~murray.saul/uli101/stuff.txt</span>
'''PART APart B: WRITE BASH SHELL SCRIPT CODEWriting Linux Commands Using the sed Utility'''
# Write a Bash shell script that clears Linux sed command to display only lines 5 to 9 for the screen and displays the text Hello World on the screenfile: '''~murray.saul/uli101/stuff.<br><br><br><br><br>What permissions are required to run this Bash shell script?<br><br><br>What are the different ways that you can run this Bash shell script from the command line?<br>txt'''<br><br># Write a Bash shell script that clears Linux sed command to display only lines the screen, prompts begin the user pattern “and” for their '''full name''' and then prompts the user for their file: '''age~murray.saul/uli101/stuff.txt''',<br>then clears the screen again and welcomes the user by their name and tells them their age.<br> <br><br><br><br><br><br><br>What comments would you add # Write a Linux sed command to display only lines that end with a digit for the above script’s contents to properly document this Bash shell script to be understood<br>for those users that would read file: '''~murray.saul/uli101/ edit this Bash shell script’s contents?<br> stuff.txt'''<br><br># Write a Bash shell script Linux sed command to save lines that will first set match the pattern “line” (upper or lowercase) for the value of a variable called file: '''number~murray.saul/uli101/stuff.txt''' and save results (overwriting previous contents) to : '''23''' and make this variable '''read-only~/results.txt'''.<br>Then the script will clear the screen and prompt the user to enter a value for that variable called number to another value.<br>Have the script display the value of the variable called number to prove that it is a read-only variable.<br><br><br><br><br>When you ran this Bash shell script, did you encounter an error message?<br>How would you run this Bash shell script, so the error message was NOT displayed?<br><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. Also have the Bash shell script display the number of arguments that were entered after your Bash shell script.<br><br><br><br><br><br><br><br>
'''Write Part C: 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'''
<pre>
</pre>
'''Write the results of each of the following Linux commands for the above-mentioned file:'''
# <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>
'''Part D: Writing Linux Commands Using the awk Utility'''
Write a single Linux command to perform the specified tasks for each of the following questions. # 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>
[[Category:ULI101]]