= KEY CONCEPTS =
===Regular Expressions vs. Filename Expansion===
[[Image:re-1.png|thumb|right|350px|'''Filename expansion symbols''' allow the Linux shell to expand filenames as arguments (referred to as “globbing”).]]<br>In a previous tutorial, you learned that '''filename expansion symbols''' allow the Linux shell to expand filenames as arguments (referred to as “globbing”) for file management commands. This is very useful for managing multiple files sharing similar characteristics such as the same file extension.
''Filename Expansion symbols'' are used to search, edit and manipulate text and are used with Linux file management commands such as '''ls''', '''rm''', '''mv''', '''cp''', '''cat''', '''less''', '''more''', '''head''', '''tail''', '''sort''', '''uniq''', '''cut''', '''tr''', and '''wc'''.<br><br>
[[Image:re-2.png|thumb|right|250px|'''Concept''' of matching a simple pattern of text contained within a text file.]]
<i>A '''regular expression''' is a combination of two types of characters: '''literals''' and '''special characters'''.<br>In combination, these characters define a logical pattern. Strings of text can be compared to this pattern<br>to see if they fit the pattern defined by the expression.</i>
