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Tutorial11: Sed & Awk Utilities

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→‎INVESTIGATION 1: USING THE SED UTILITY

# Issue a Linux command to create a directory called '''sed'''

# Issue a Linux command to change to the '''sed''' directory and confirm that you are located in the '''sed''' directory.

# Issue the following ~~linux~~ Linux command to download the data.txt file ('''copy and paste''' to save time): wget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/data.txt</nowiki>

# Issue the '''more''' command to quickly view the contents of the '''data.txt''' file. When finished, exit the more command by pressing the letter q[[Image:sed-1.png|thumb|right|300px|Issuing the '''p''' instruction without using the '''-n''' option (to suppress original output) will display lines twice.]] The '''p''' instruction with the '''sed''' command is used to '''print''' (i.e. ''display'') the contents of a text file.

# Issue the following ~~linux~~ Linux command: sed 'p' data.txt '''NOTE: You should notice that each line appears twice'''. The reason why standard output appears twice is that the sed command (without the '''-n option''') displays all lines regardless of an address used. We will use '''pipeline commands''' to both display stdout to the screen and save to files for confirmation of running these pipeline commands when run a '''checking-script''' later in this investigation. # Issue the following ~~linux~~ Linux pipeline command: sed -n 'p' data.txt | tee sed-1.txt What do you notice? You should see only one line. You can specify an address (''line #'', '''line #s''' or range of '''line #s''') when using the sed utility. # Issue the following ~~linux~~ Linux pipeline command: sed -n '1 p' data.txt | tee sed-2.txt You should see the first line of the text file displayed. [[Image:sed-2.png|thumb|right|500px|Using the sed command to display a '''range''' of lines.]]# Issue the following ~~linux~~ Linux pipeline command: sed -n '2,5 p' data.txt | tee sed-3.txt What is displayed? How would you modify the sed command to display the line range 10 to 50? The '''s''' instruction is used to '''substitute''' text (a similar to method was demonstrated in the vi editor in tutorial 9). # Issue the following ~~linux~~ Linux pipeline command: sed '2,5 s/TUTORIAL/LESSON/g' data.txt | tee sed-4.txt | more What do you notice? View the original contents of lines 2 to 5 in the '''data.txt''' file in another shell to confirm that the substitution occurred. [[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. # Issue the following ~~linux~~ Linux pipeline command: sed '11 q' data.txt | tee sed-5.txt What did you notice? You can use regular expressions to select lines that match a pattern. The rules remain the same for using regular expressions as demonstrated in tutorial9 except the regular expression must be contained within '''delimiters''' such as the forward slash "/" when using the sed utility. [[Image:sed-4.png|thumb|right|400px|Using the sed command using regular expressions with '''anchors'''.]]# Issue the following ~~linux~~ Linux pipeline command: sed -n '/^The/ p' data.txt | tee sed-6.txt What do you notice? # Issue the following ~~linux~~ Linux pipeline command: sed -n '/d$/ p' data.txt | tee sed-7.txt What do you notice? The '''sed''' utility can also be used as a '''filter''' to manipulate text that was generated from ~~linux~~ Linux commands. [[Image:sed-5.png|thumb|right|400px|Using the sed command with '''pipeline''' commands.]]# Issue the following ~~linux~~ Linux pipeline command: who | sed -n '/^[a-m]/ p' | tee sed-8.txt | more What did you notice? # Issue the following ~~linux~~ Linux pipeline command: ls | sed -n '/txt$/ p' | tee sed-9.txt What did you notice?

# Issue the following to run a checking script: bash /home/murray.saul/myscripts/week11-check-1 If you encounter errors, make corrections and '''re-run''' the checking script until you receive a congratulations message, then you can proceed.

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Tutorial11: Sed & Awk Utilities

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