13,420
edits
Changes
→INVESTIGATION 1: SIMPLE & COMPLEX REGULAR EXPRESSIONS
# To demonstration, issue the following command to display zero or more occurrences of the letter x:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "x*" textfile1.txt | more</span><br><br>You will most likely notice most lines of the file is displayed.<br><br>
# Let's issue a command to display strings that contain more than one occurrence of the letter x:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "xx*" textfile1.txt | more</span><br><br>Why did this work? because the pattern indicates one occurrence of the letter x, followed by zero or MORE occurrences of the letter x.<br><br>If you combine the complex regular expression symbols .* it will act like zero or more occurrence of any character (like * did in filename expansion).<br><br>
# Issue the following command to match strings begin and end with a number with nothing or anything inbetween:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9].*[0-9]$" textfile1.txt | more</span><br><br>Using simultaneous anchors combined with the .* symbol(s) can help you to refine your search patterns of strings.<br><br># xIssue the following linux pipeline command to display strings that begin with a capital letter, ends with a number, and contains a capital X somewhere inbetween:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[A-Z].*X.*[0-9]$" textfile1.txt | more</span>
=INVESTIGATION 2: EXTENDED REGULAR EXPRESSIONS =
