~~Title: Regular Expressions ~~
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The //Regular Expressions// mode lets you perform batch renaming using regular expressions to specify search and replace patterns.

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The example above shows a very simple regular expression that has been used to remove the underscore from the original filenames. The **Old name** pattern of //(.*)_(.*)// uses parentheses to tag two "match anything" expressions, and the //\1\2// in the **New name** pattern inserts the values of the two tagged expressions in the new name.

An extension Directory Opus provides is the ability to perform a repeating search and replace using regular expressions. The above example will only remove a single underscore, but if you wanted to remove all underscores from the source name, you can append a # (pound/hash) sign to the **Old name** pattern. This causes Opus to repeat the search and replace until the new filename no longer changes.



See the [[:reference:wildcard_reference:regular_expression_syntax|Regular Expression Syntax]] reference page for more information about using regular expressions. Additional information can be found in  [[http://msdn.microsoft.com/en-us/library/bb982727.aspx|Microsoft's introduction to TR1 ECMAScript]] (the flavor of regular expressions that Opus uses by default) for more information, and you can ask on the [[http://resource.dopus.com/|Opus Resource Centre]] if you need help.