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# Issue the following linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "the" textfile1.txt</span><br><br>You should now see only strings of text that match the word '''"the"''' (upper or lower case).<br><br>Matching literal or simple regular expressions can be useful, but are '''limited'''<br>in what they can assist with pattern matching. For example, you may want to<br>search for a pattern located at the '''beginning''' or '''end''' of the string.<br><br>There are other regular expression symbols that provide more '''precise''' pattern matches.<br>These special characters are known as '''complex''' and '''extended''' regular expressions symbols.<br> In this section, we will focus on complex ''regular expressions'' and then discuss<br>''extended regular expressions'' in INVESTIGATION 2.<br><br>

# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "^the" textfile1.txt</span><br><br>The '''^''' symbol is referred to as an '''anchor'''. In this case, it only matches<br>the word "'''the'''" (both upper or lowercase) at the <u>beginning</u> of the string.<br><br>

# Issue the following Linux pipeline command to anchor the '''word''' "the" simultaneously<br>at the <u>beginning</u> and <u>end</u> of the string:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "^the$" textfile1.txt </span><br><br>What do you notice?<br><br>Anchoring patterns at both the <u>beginning</u> and <u>ending</u> of strings can greatly assist<br>for more robust search patterns.<br><br>We will now be demonstrating the usefulness of '''simultaneous anchoring'''<br>with other complex regular expressions symbols.<br><br>

# Issue the following command to match strings that begin with 3 characters:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^..." textfile1.txt</span><br><br>What do you notice? Can lines that contain '''less than 3 characters''' be displayed?<br><br>