13,420
edits
Changes
→INVESTIGATION 2: USING THE AWK UTILITY
# Issue a Linux command to <u>change</u> to the '''awk''' directory and confirm you are located in the '''awk''' directory.<br><br>
# 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<br>to print all selected lines that match a '''pattern'''.<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 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/ {print}' cars.txt</span><br><br>We will use '''pipeline commands''' to both display stdout to the screen and save to files<br>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 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 | tee awk-1.txt</span><br><br>What do you notice? You should notice ALL lines displayed without using a search criteria.<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>