13,420
edits
Changes
no edit summary
=INTRODUCTION TO SHELL SCRIPTINGUSING SED & AWK UTILTIES=
<br>
===Main Objectives of this Practice Tutorial===
:* Understand Use the process for '''planningsed''' prior 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 linesed''' contained at the top of a shell scriptcommand.
:* Setting Use the '''permissionssed''' for command as a shell script and properly '''executefilter''' a shell scriptwith Linux pipeline commands.
:* Understand and use Use the '''environmentawk''' and command to '''user-defined''''''Bold manipulate text''' variables within contained in a shell scriptfile.
:* Understand List and explain '''comparison operators''', '''variables''' and '''actions''' associated with the purpose of '''control flow statementsawk''' used with shell scriptscommand.
:* Use the '''testawk''' command to test various conditions. :* Use the '''ifas a ''' logic statement and the filter'''for''' loop statement within shell scriptswith Linux pipeline commands.<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]
|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:'''
* Can use a line number, to select a specific line (for example: '''5''Example')* Can specify a range of line numbers (for example:<br><br><span style="font-family:courier;">chmod u+x myscript'''5,7''')* Regular expressions are contained within forward slashes (e.bash<br>g./myscript.bash<br>regular-expression/home/username/myscript)* Can specify a regular expression to select all lines that match a pattern (e.bash<br>~g '''/myscript^[0-9].bash<*[0-9]$/span>''') * If NO address is present, the instruction will apply to ALL lines
<br><br>
===Using Control Flow Statements in Shell Scriptsthe awk Utility===
* The '''Logic Statementsawk''' 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.* The '''–F''' option can be used to specify the default '''field delimiter''' (separator) character<br>eg. '''awk –F”;”''' (would indicate a semi-colon delimited input file).<br>'''Selection Criteria'''
<span style="color:red;">'''Loop StatementsATTENTION''': 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</span><br><br>
'''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 '''sed'''<br><br># Issue a Linux command to <u>change</u> to the '''confirmsed''' 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 the shell and that We will use '''sedpipeline commands''' wouldn't be an appropriate shell script name to use.both display stdout to the screen and save to files<br>for <u>confirmation<br/u># Use of running these pipeline commands when run a '''text editorchecking-script''' like vi or nano to create later in this investigation.<br><br># Issue the text file called hello (eg. following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">vi hellosed -n 'p' data.txt | tee sed-1.txt</span>)<br><br>If What do you are notice? You should see only one line.<br><br>You can specify an '''address''' to display lines using the nano text editorsed utility<br>(eg. ''line #'', refer to notes on text editing in a previous week in the course schedule'''line #s''' or range of '''line #s''').<br><br># 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 '1 p' data.txt | tee sed-2.txt</span><br>esirst add execute permissions prior <br>You should see the first line of the text file displayed.<br>What other command is used to running only display the shell script.first line in a file?<br><br>[[Image:sed-2.png|thumb|right|500px|Using the sed command to display a '''range''' of lines.]]# 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 '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># Re-run your shell scriptIssue the following Linux pipeline command: <br><span style="color:blue;font-weight:bold;font-family:courier;">sed '2,5 s/TUTORIAL/LESSON/g' data./hellotxt | tee sed-4.txt | more</span><br><br>Although your shell script should work, it is recommended What do you notice? View the original contents of lines 2 to force your shell script to run in a specific shell. This helps prevent your shell script encountering errors when run 5 in the incorrect shell (i'''data.e. syntax not recognized txt''' file<br>in a specific 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 '''Editq''' your instruction terminates or '''helloquits''' shell script using the execution of the sed utility as soon as it is read in a text editorparticular line or matching pattern.<br><br># Insert Issue the following line at 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 '''beginningregular 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 '''firstforward slashes''' line of your hello file:<br>(eg. <span style="font-family:courier;font-weight:bold;">#!/binregexp/bash</span>).<br><br>This is referred to as a [[Image:sed-4.png|thumb|right|400px|Using the sed command using regular expressions with '''she-bang lineanchors'''. It forces ]]# Issue the script to be run in 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 Bash Shellfollowing Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">sed -n '/d$/ p' data. When your Bash Shell script finishes execution, txt | tee sed-7.txt</span><br><br>What do you are returned notice?<br><br>The '''sed''' utility can also be used as a '''filter''' to your current shell manipulate text that you are using (which in our case in Matrix, is still the Bash shell)<br>was generated from Linux commands.<br><br>[[Image:sed-5.png|thumb|right|400px|Using the sed command with '''pipeline''' commands.]]# Save your editing changes and exit your text editorIssue 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># It is a good idea to rename your shell script to include an extension to indicate that the file is a Bash Shell script file. Issue the following linux Linux pipeline command to rename your shell script file:<br><span style="color:blue;font-weight:bold;font-family:courier;">mv hello hellols | sed -n '/txt$/ p' | tee sed-9.bashtxt</span><br><br>What did you notice?<br><br># Run your renamed shell script by issuing Issue the followingto run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">.~uli101/hello.bashweek11-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>
=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:'''
# Use Change to your '''home''' directory and issue a text editor command to edit the shell script '''confirm'''<br>you are located in your ''home'' directory.<br><br># Issue a Linux command to create a directory called '''hello.bashawk'''<br><br># Add the following line Issue a Linux command to <u>change</u> to the bottom of '''awk''' directory and confirm you are located in the '''awk''' directory.<br><br>Let's download a database filethat 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;">echo "The current shell you are using iswget <nowiki>https: $SHELL"//ict.senecacollege.ca/~murray.saul/uli101/cars.txt</nowiki></span><br><br># Save your editing changes and exit your text editorIssue 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 change to display all lines (i.e. records) in the '''cars.txt''' database that matches the Bourne Shell pattern (a different shell than the default Bashor "make")called '''ford''':<br><span style="color:blue;font-weight:bold;font-family:courier;">shawk '/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 confirm you are display records<br>in the Bourne Shell'''cars.txt''' database that contain the pattern (i.e. make) '''ford''':<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $SHELLawk '/ford/' cars.txt | tee awk-1.txt</span><br><br>What do you notice? You should see 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 output of following variables in this tutorial:<br><br>[[Image:awk-2.png|thumb|right|400px|Using the awk command that you are located 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 the Bourne Shellcurrent record<br><br>For a listing of more variables, please consult your course notes.<br><br># Run your Issue the following linux pipeline command to display the '''model''', '''year''', '''quantity''' and price<br>in the '''hellocars.bashtxt'''database for makes of '' shell script'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>What shell does Notice that a '''space''' is the delimiter for the shell script indicate fields that appear as standard output.<br><br>The '''tilde character''' '''~''' is running?used to search for a pattern or display standard output for a particular field.<br><br>This is because there is NO shebang line so this Bash shell script is being run in # Issue the Bourne Shellfollowing 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>LetYou can also use '''comparison operators'''s add a sheto 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-bang line 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 top of this shell script file so it forces the shell script following linux pipeline command to run in display display the Bash Shell instead '''car make''', '''model''', '''quantity''' and '''price''' of the Bourne Shellall 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># Use a text editor Issue the following linux pipeline command to edit the shell script called display display '''price''',<br>'''quantity''', '''model''' and '''car make''' of vehicles whose '''prices are less than $5,000''hello.bash':<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># Add Issue the following line linux pipeline command to display the TOP '''car make''',<br>'''year''' and '''quantity''' of cars that '''begin''' with the file'''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 ~ /binford/bash&& $5 > 10000 {print $0}' cars.txt | tee awk-7.txt</span><br><br># Run your Issue the following linux command ('''hello.bashcopy and paste''' shell scriptto 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>What shell does # Issue the '''cat''' command to quickly view the contents of the shell script indicate is running?'''cars2.txt''' file.<br><br>This is because of # Issue the shebang line indicating following linux pipeline command to run display the '''year'''<br>and '''quantity''' of cars that '''begin''' with the shell script in '''letter 'f'''' for the Bash shell although '''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 ran this script within 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 Bourne Shellsecond and fourth fields.<br><br>LetYou need to issue awk with the -F option to indicate that this file's add fields are separated (delimited) by a shesemi-bang line colorn.<br><br># Issue the following linux pipeline command to display the top '''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 shell script file so it forces time?<br><br># Issue the shell following to run a checking script to :<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 in ''' the Bash Shell instead of the Bourne Shellchecking script until you<br>receive a congratulations message, then you can proceed.<br><br>
= LINUX PRACTICE QUESTIONS =
The purpose of this section is to obtain '''extra practice''' to help with '''quizzes''', your '''midterm''', and your '''final exam'''.
https://ict.senecacollege.ca/~murray.saul/uli101/uli101_week11_practice.docx
'''Part A: Display Results from Using the sed Utility'''
Note the contents from the following tab-delimited file called '''~murray.saul/uli101/stuff.txt''':
(this file pathname exists for checking your work)
Write the results of each of the following Linux commands for the above-mentioned file: Before learning about logic and loop control-flow statements, you need to first learn about issuing test conditions using the '''test''' command.
# 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 previouslysed -issued n '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $?</span><br><br>Based on its value3, 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 6 p'''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">echo $?<~murray.saul/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 $course != "uli101"</span><br><br># Issue a linux command to display the value of '''$?'''stuff. 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 > $number2txt</span><br><br># Issue a linux command to display the value of '''$?'''. '''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 10</span><br><br>You should notice a file called "'''10'''". The incorrectly issued '''test''' command used redirect to create an empty file instead,<br> which indeed succeeded just giving a TRUE value!<br><br>To prevent these incorrectly issued testing for number comparison, you can use the following options instead:<br>'''-lt''' (<), '''-le''' (<=), '''-gt''' (>), '''-ge''' (>=;), '''-eq''' (=), '''-ne''' (!=)<br><br># Issue the correct linux command to properly test both values:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $number1 -gt $number2</span><br><br># Issue a linux command to display the value of '''$?'sed '4 q'~murray. You should notice that the exit status value is now FALSE which is the correct result.<br><br># The '''test''' command can be abbreviated by the square brackets [ ] which contain the test condition within the square brackets. You need to have spaces between the brackets and the test condition; otherwise, you will get a test error.<br><br># To generate a test error, issue the improper use of the '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">[$number1 -gt $number2]<saul/span><br><br>You should notice an test error message.<br><br># Issue the correct use of the '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">[ $number1 -gt $number2 ]<uli101/span><br><br>Issue a command to view the value of the exit status of the previously issued '''test''' command. You should notice that is works properlystuff.<br><br>'''Let's now learn about control-flow statements:'''<br><br>'''Logic statements''' are to create different paths or directions that the script can execute based in the result of testing conditions. In this tutorial, we will only focus on the '''if''' logic statement.<br><br># Use a text editor like vi or nano to create the text file called '''if-1.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-1.bashtxt</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br># Enter the following lines in your shell script:<br><span style="font-family:courier;">#!/bin/bash<br>clear<br>num1=5<br>num2=10<br>if [ $num1 -gt $num2 ]<br>then<br> echo "Greater Than"<br>fi</span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').<br><br># Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x if-1.bash</span><br><br># Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./if-1.bash</span><br><br>Confirm that the output indicated a correct result.<br><br># Use a text editor like vi or nano to create the text file called '''if-2.bashsed ''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-2.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br># Enter the following lines in your shell script:<br><span style="font-family:courier;">#!/bin/bash<br>clear<br>read -p "Enter the first number: " num1<br>read -p "Enter the second number: " num2<br>if [ $num1 -gt $num2 ]<br>then<br> echo "The first number is greater than the second number."<br>fi</span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by 'd''ENTER''').<br><br># Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x if-2~murray.bash<saul/span><br><br># Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">.uli101/if-2.bash</span><br><br>Confirm that the output indicated a correct result.<br><br>What happens when you enter a first number that is less than or equal to the second number? We will learn about if-else and if-elif-else statements in a couple of weeks.<br><br>'''Loop statements''' are used to provide repetition in a shell script. In this tutorial, we will only focus on the '''for''' loop statement.<br><br># Use a text editor like vi or nano to create the text file called '''for-1.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi for-1.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedulestuff.<br><br># Enter the following lines in your shell script:<br><span style="font-family:courier;">#!/bin/bash<br>clear<br>for 5 4 3 2 1<br>do<br> echo $x<br>done<br>echo "blast-off!"txt</span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').<br><br># Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x for-1.bash</span><br><br># Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./for-1.bash</span><br><br># Use a text editor like vi or nano to create the text file called sed '''for-2.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi for-2.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br># Enter the following lines in your shell script:<br><span style="font-family:courier;">#!s/binline/bash<br>clear<br>for x<br>do<br> echo $x<br>done<br>echo "blast-off!"<NUMBER/span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type g''':wx''' followed by '''ENTER''')~murray.<br><br># Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x for-2.bash<saul/span><br><br># Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">.uli101/for-2stuff.bash 10 9 8 7 6 5 4 3 2 1txt</span><br><br>How does this differ from the previous shell script?<br><br>You will learn in a couple of weeks more examples of using loop statements.<br><br># After you complete the Review Questions sections to get additional practice, then work on your '''online assignment 3''',<br>'''sections 2 and 3''' labelled '''Interactive Shell Environment''' and '''Introduction To Scripting (phone)'''.<br><br>
'''Review QuestionsPart C:Writing Linux Commands Using the awk Utility'''
Note the contents from the following tab-delimited file called '''~murray.saul/uli101/stuff.txt''':
(this file pathname exists for checking your work)
'''Write the results of each of the following Linux commands for the above-mentioned file:'''
# 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]]