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→INVESTIGATION 2: USING THE AWK UTILITY
:* Use the '''sed''' command to '''manipulate text''' contained in a file.
:* List and understand explain several '''instructions''' associated with the '''sed''' command.
:* Use the '''sed''' command as a '''filter''' with Linux pipeline commands.
:* Use the '''awk''' command to '''manipulate text''' contained in a file.
:* List and explain several '''comparison operators''' and variables associated with the '''awk''' command.
:* Use the '''awk''' command as a '''filter''' with Linux pipeline commands.
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===Tutorial Reference Material===
| 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;" |Man Pages
'''Usage:'''
<span style="color:blue;font-weight:bold;font-family:courier;">awk options 'selection _criteria -criteria {action }’ file-name</span>
# 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 '''more''' command to quickly view the contents of the '''cars.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><br><br>The "'''print'''" action (command) is the <u>default</u> action of awk to print all selected lines that match a pattern.<br>This action (contained in braces) can provide more options such as printing specific fields of selected lines (or records) from a database.<br><br>
# Issue the following linux command all to display records in the "cars.txt" database that contain the make "ford":<br><span style="color:blue;font-weight:bold;font-family:courier;">wget awk '/ford/ {print}' cars.txt</span><br><br>
# Issue the following linux command all to display records in the "cars.txt" database that contain the make "ford":<br><span style="color:blue;font-weight:bold;font-family:courier;">awk '/ford/' cars.txt</span><br><br>What do you notice?<br><br>You can use variables with the "print" action for further processing. We will discuss the following variables in this tutorial:<br><br>'''$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>The '''tilde character''' '''~''' is used to search for a pattern or display standard output for a particular field.<br><br>
# Issue the following linux command to display the model, year, quantity and price 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</span><br><br>Notice that a space " " is the delimiter for the fields that appear as standard output.<br><br>
Write the results of each of the following Linux commands for the above-mentioned file:
# <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 '4 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 B: Writing Linux Commands Using the sed Utility'''
# <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>
