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Tutorial3: Advanced File Management / Quoting Special Characters

366 bytes added, 11:25, 17 January 2021

→‎INVESTIGATION 1: ABSOLUTE / RELATIVE / RELATIVE-TO-HOME PATHNAMES

# Issue the following Linux command: cp /bin/ls ./ls.bk What does this command do? Let's run a checking script to make certain you performed the a few of the recently-issued commands correctly.

# Issue the following: bash /home/murray.saul/scripts/week3-check-2

# If you encounter errors, make ~~correct~~ corrections and then re-run the checking script until you receive a congratulations message, and proceed to the next INVESTIGATION.

=INVESTIGATION 2: FILENAME EXPANSION=

<div style="font-family:courier;margin-left:50px;font-weight:bold;">abc.txt def.text hij.TxT 1a4.txt 123.TXT 456.txt 6u9.txt

ab2.html 1234.txt abcdef.txt abcde.txt </div>

<ol><li value="4">To verify that you properly created those files, issue the following: bash /home/murray.saul/scripts/week3-check-3 If you encounter errors, then make corrections (eg. '''viewing directory contents''', '''check for correct filename syntax''', '''case sensitivity''', '''missing files''', '''files in the wrong location''', etc.) and then re-run the checking script until you receive a congratulations message, and then continue with this section. '''ATTENTION''': Learning to '''fix your mistakes''' by issuing Linux commands may be required if you make mistakes in your Assignment #1. This advice should help to prevent '''wasting time''' completing later sections of your assignment #1. <li>Issue the '''ls''' command to get a listing of files in your ''examples'' directory. The output should look identical to the diagram displayed below. You can refer to this listing to see all files so you can then predict the output from Linux commands that use filename expansion symbols. [[Image:listing-1.png|left|650px|thumb|]] </li><li>What do you think the output will be from the following Linux command? ls ???.txt '''Write down the expected output ''' on paper, then '''issue the command ''' to check your answer. </li><li>What do you think the output will be from the following Linux command? ls ?????.txt '''Write down the expected output ''' on paper, then '''issue the command ''' to check your answer. </li><li>What do you think the output will be from the following Linux command? ls ??????.txt '''Write down the expected output on ''' on paper, then '''issue the command ''' to check your answer. </li><li>What do you think the output will be from the following Linux command? ls [0-9].txt '''Write down the expected output ''' on paper, then '''issue the command ''' to check your answer. Did the command work? What does this teach you about the character class [ ] symbol? </li><li>What do you think the output will be from the following Linux command? ls [0-9][0-9][0-9].txt '''Write down the expected output ''' on paper, then '''issue the command ''' to check your answer. </li><li>What do you think the output will be from the following Linux command? ls [a-z][a-z][a-z].txt '''Write down the expected output ''' on paper, then '''issue the command ''' to check your answer. </li><li>What do you think the output will be from the following Linux command (using character class with UPPERCASE letters)?: ls [A-Z][A-Z][A-Z].txt '''Write down the expected output ''' on paper, then '''issue the command ''' to check your answer. </li><li>What do you think the output will be from the following Linux command (using character class using alpha-numeric characters)? ls [a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9].txt '''Write down the expected output ''' on paper, then '''issue the command ''' to check your answer. </li><li>What do you think the output will be from the following Linux command? ls *.txt '''Write down the expected output ''' on paper, then '''issue the command ''' to check your answer. Did ALL text files get listed? Why not? </li><li>What do you think the output will be from the following Linux command? ls *.[tT][xX][tT] '''Write down the expected output on ''' on paper, then '''issue the command ''' to check your answer.Did ALL text files get listed this time? If so, why? </li><li>'''NOTE:''' We have just been using filename expansion symbols just with the ls command. Filename expansion symbols can be used for ANY Linux file management command (e.g. '''cat''', '''more''', '''less''', '''cp''', '''mv''', '''rm''', '''ls''', etc.). Let's get some practice issuing these other Linux file management commands. </li><li>Issue the following Linux command: file *.[tT][xX][tT] What is the purpose of this command? Which files are contained in this output? <li>[[Image:dir12.png|right|350px|thumb|]]Change to the '''commands''' directory using an '''absolute''' pathname (use the diagram on right-side for reference). </li><li>Issue a Linux command to confirm that you are now in the '''commands''' directory. </li><li>Issue the following Linux command~~: <~~(lowercase "l" NOT the number "1"): cp /bin/l.*   . View the contents of the contents directory. What did this command do? </li><li>Issue the following Linux command: rm * View the contents of the contents directory. What did this command do? </li><li>Issue the following Linux command(lowercase "l" NOT the number "1"): cp /bin/l?   . View the contents of the contents directory. What did this command do? </li><li>Issue the following Linux command: rm l[!s] View the contents of the contents directory. What did this command do? </li><li>Use a text editor (nano or vi) to create the file called '''ab''' in the '''commands''' directory that contains the line of text below, and then save editing changes to this file: This is file ab </li><li>Use a text editor (nano or vi) to create the file called '''cd''' in the '''commands''' directory that contains the line of text below, and then save editing changes to this file: This is file cd </li><li>Use a text editor (nano or vi) to create the file called '''ef''' in the '''commands''' directory that contains the line of text below, and then save editing changes to this file: This is file ef </li><li>Issue the following Linux command: cat ?? View the contents of the contents directory. What did this command do? Why does the output look strange? '''NOTE:''' Press the keys '''ctrl-c''' to return to the shell prompt. </li><li>Issue the following Linux command: cat [!l][!s] View the contents of the contents directory. What did this command do? Does the output look better? If so, why? </li></ol>

: Proceed to the next INVESTIGATION.

= INVESTIGATION 3: QUOTING SPECIAL CHARACTERS =

As discussed in the above section, there are some special characters that the shell uses to perform an operation including the filename expansion ~~symbols~~symbol: '''*''' ~~or '''?'''~~

There is a method ~~to instruct~~ make the ~~Linux~~ shell to '''ignore the purpose of special characters''' and treat as '''regular text'''.

In this section, you will learn '''three unique methods''' to quote special characters.

:'''Perform the Following Steps:'''

[[Image:quotation.png|right|350px|thumb|Using quotation to make the shell '''ignore the purpose of special characters''' and treat as '''regular text'''.]]

# Issue a Linux command to confirmed that you are still in the '''commands''' directory (if not, change to the ''commands'' directory and confirm).

# Issue the following Linux command: echo hello there '''NOTE:''' the '''echo''' command is used to display text onto your terminal.

# Issue the following Linux command: echo '* hello *' Is there any difference between this command and the two previous commands?

# Issue the following Linux command: echo $USER '''NOTE''': The environment variable '''USER''' contains the current user's login name. The '''$''' character immediately followed by the environment variable name causes it to expand to the '''value''' that the variable contains.

# Issue the following Linux command (using single quotes): echo '* $USER*' What happened? Why is the output display like this? # Issue the following Linux command (using double quotes): echo "* $USER*" What happened? Why? # Let's use quoting special characters for a couple of other commands. Move to the '''lesson2''' directory. Confirm that you are currently located in the ''lesson2'' ~~directory. # Issue the following Linux command: cp /bin/ls . # Issue the '''ls''' command to verify that there are copied files in your lesson2~~ directory. '''NOTE:''' Although it is NOT RECOMMENDED to create a filename using a special character (remember ~~that~~ file naming ~~rule~~rules?), we will create an empty file called "*"

# Issue the following Linux command (using single quotes): touch '*'

# Issue the '''ls''' command. Do you now see a file called "*" in addition to the other copied files?

# Issue the following Linux command: cp /bin/ls .

# Issue the following Linux command (using single quotes): touch '*'

# Issue the '''ls''' command to view the files in your current directory.

# Issue the following Linux command (using single quotes): rm '*'

# Issue the '''ls''' command to confirm that the file called "*" has been removed in your current directory. What happened this time?

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