Regular Expression

A Regular Expression contains one or more of the following:

• A character set. These are the characters retaining their literal meaning. The simplest type of Regular Expression consists only of a character set, with no metacharacters.
• 
  An anchor. These designate (anchor) the position in the line of text that the RE is to match. For example, ^, and $ are anchors.
• Modifiers. These expand or narrow (modify) the range of text the RE is to match. Modifiers include the asterisk, brackets, and the backslash.

The main uses for Regular Expressions (REs) are text searches and string manipulation. An RE matches a single character or a set of characters -- a string or a part of a string.

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