169 lines
6.2 KiB
Markdown
169 lines
6.2 KiB
Markdown
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# Lesson 3.1
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## Guided Exercises
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1. According to the extensions, which of the following tools were used to create these files?
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* archive.tar
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* archive.tgz
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* archive.tar.xz
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1. According to the extensions, which of these files are archives and which are compressed?
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* file.tar
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* file.tar.bz2
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* file.zip
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* file.xz
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1. How would you add a file to a gzip compressed tar file?
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1. Which tar option instructs tar to include the leading / in absolute paths?
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1. Does zip support different compression levels?
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## Explorational Exercises
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1. When extracting files, does tar support globs in the file list?
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1. How can you make sure a decompressed file is identical to the file before it was compressed?
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1. What happens if you try to extract a file from a tar archive that already exists on your filesystem?
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1. How would you extract the file archive.tgz without using the tar z option?
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# Lesson 3.2.1
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## Guided Exercises
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1. List the contents of your current directory, including the ownership and permissions, and redirect the output to a file called contents.txt within your home directory.
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1. Sort the contents of the contents.txt file from your current directory and append it to the end of a new file named contents-sorted.txt.
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1. Display the last 10 lines of the /etc/passwd file and redirect it to a new file in your user’s Documents directory.
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1. Count the number of words within the contents.txt file and append the output to the end of a file field2.txt in your home directory. You will need to use both input and output redirection.
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1. Display the first 5 lines of the /etc/passwd file and sort the output reverse alphabetically.
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1. Using the previously created contents.txt file, count the number of characters of the last 9 lines.
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1. Count the number of files called test within the /usr/share directory and its subdirectories. Note: each line output from the find command represents a file.
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## Explorational Exercises
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1. Select the second field of the contents.txt file and redirect the standard output and error output to another file called field1.txt.
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1. Using the input redirection operator and the tr command, delete the dashes (-) from the contents.txt file.
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1. What is the biggest advantage of only redirecting errors to a file?
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1. Replace all recurrent spaces within the alphabetically sorted contents.txt file with a single space.
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1. In one command line, eliminate the recurrent spaces (as done in the previous exercise), select the ninth field and sort it reverse alphabetically and non-case sensitive. How many pipes did you have to use?
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# Lesson 3.2.1
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## Guided Exercises
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1. Using grep and the /usr/share/hunspell/en_US.dic file, find the lines that match the following criteria:
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* All lines containing the word cat anywhere on the line.
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* All lines that do not contain any of the following characters: sawgtfixk.
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* All lines that start with any 3 letters and the word dig.
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* All lines that end with at least one e.
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* All lines that contain one of the following words: org , kay or tuna.
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* Number of lines that start with one or no c followed by the string ati.
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## Explorational Exercises
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1. Find the regular expression that matches the words in the “Include” line and doesn’t match the ones in the “Exclude” line:
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* Include: pot, spot, apot
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* Exclude: potic, spots, potatoe
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* Include: arp99, apple, zipper
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* Exclude: zoo, arive, attack
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* Include: arcane, capper, zoology
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* Exclude: air, coper, zoloc
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* Include: 0th/pt, 3th/tc, 9th/pt
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* Exclude: 0/nm, 3/nm, 9/nm
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* Include: Hawaii, Dario, Ramiro
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* Exclude: hawaii, Ian, Alice
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1. What other useful command is commonly used to search within the files? What additional functionalities does it have?
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1. Thinking back at the previous lesson, use one of the examples and try to look for a specific pattern within the output of the command, with the help of grep.
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# Lesson 3.3.1
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1. The user types the following to their shell:
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```
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$ PATH=~/scripts
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$ ls
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Command 'ls' is available in '/bin/ls'
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The command could not be located because '/bin' is not included in the PATH environment variable.
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ls: command not found
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```
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* What has the user done?
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* What command will combine the current value of PATH with the new directory ~/scripts?
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1. Consider the following script. Notice that it is using elif to check for a second condition:
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```
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> /!bin/bash
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> fruit1 = Apples
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> fruit2 = Oranges
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if [ $1 -lt $# ]
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then
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echo "This is like comparing $fruit1 and $fruit2!"
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> elif [$1 -gt $2 ]
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then
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> echo '$fruit1 win!'
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else
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> echo "Fruit2 win!"
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> done
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```
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* The lines marked with a > contain errors. Fix the errors.
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1. What will the output be in the following situations?
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```
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$ ./guided1.sh 3 0
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$ ./guided1.sh 2 4
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$ ./guided1.sh 0 1
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```
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## Explorational Exercises
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1. Write a simple script that will check if exactly two arguments are passed. If so, print the arguments in reverse order. Consider this example (note: your code may look different than this, but should lead to the same output):
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```
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if [ $1 == $number ]
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then
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echo "True!"
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fi
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```
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1. This code is correct, but it is not a number comparison. Use an internet search to discover how this code is different from using -eq.
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1. There is an environment variable that will print the current directory. Use env to discover the name of this variable.
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1. Using what you have learned in questions 2 and 3, write a short script that accepts an argument. If an argument is passed, check if that argument matches the name of the current directory. If so, print yes. Otherwise, print no.
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# Lesson 3.3.2
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## Guided Exercises
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1. Read the contents of script1.sh below:
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```
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#!/bin/bash
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if [ $# -lt 1 ]
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then
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echo "This script requires at least 1 argument."
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exit 1
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fi
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echo $1 | grep "^[A-Z]*$" > /dev/null
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if [ $? -ne 0 ]
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then
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echo "no cake for you!"
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exit 2
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fi
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echo "here's your cake!"
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exit 0
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```
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* What is the output of these commands?
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```
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./script1.sh
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echo $?
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./script1.sh cake
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echo $?
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./script1.sh CAKE
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echo $?
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```
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2. Read the contents of file script2.sh:
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```
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for filename in $1/*.txt
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do
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cp $filename $filename.bak
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done
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```
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* Describe the purpose of this script as you understand it.
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## Explorational Exercises
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1. Create a script that will take any number of arguments from the user, and print only those arguments which are numbers greater than 10.
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