Regular Expressions

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Regular Expressions

Regular expressions describe patterns in strings and can be used i.a. to determine whether a given pattern occurs in a text or not. In TreeSize regular expressions can be used to find specific files and / or folders that match the criteria specified by regular expressions

The following table shows some examples:





Any character


Matches any single character except a line break.

a.o matches "aro" in "around" and "abo" in "about" but not "acro" in "across".

Zero or more  


Matches zero or more occurrences of the preceding expression, and makes all possible matches.

a*b matches "b" in "bat" and "ab" in "about".

e.*e matches the word "enterprise".

One or more


Matches at least one occurrence of the preceding expression.

ac+ matches words that contain the letter "a" and at least one instance of "c", such as "race", and "ace".

a.+s matches the word "access".

Start of string


Matches the start of a string

^[0-9] matches strings that start with a digit.

End of string


Matches the end of a string

exe$ matches strings that end with "exe".

Beginning of word


Matches only when a word starts at this point in the text.

[[:<:]]in matches words such as "inside" and "into" that begin with the letters "in".

End of word


Matches only when a word ends at this point in the text.

ss[[:>:]] matches words such as "across" and "loss" that end with the letters "ss".

Any one character in the set


Matches any one of the characters in the []. To specify a range of characters, list the starting and ending characters separated by a dash (-), as in [a-z].

be[n-t] matches "bet" in "between", "ben" in "beneath", and "bes" in "beside" but not "bel" in "below".

Any one character not in the set


Matches any character that is not in the set of characters that follows the ^.

be[^n-t] matches "bef" in "before", "beh" in "behind", and "bel" in "below", but not "ben" in "beneath".



Matches either the expression before or the one after the OR symbol (|). Mostly used in a group.

(sponge|mud) matches "sponge bath" and "mud bath.

Escape character


Matches the character that follows the backslash (\) as a literal. This lets you find the characters that are used in regular expression notation, such as { and ^.

\^ searches for the ^ character.

Repeat n times


Matches n occurrences of the preceding expression.

[0-9]{4} matches any 4-digit sequence.



Lets you group a set of expressions together. If you want to search for two different expressions in a single search, you can use the Grouping expression to combine them.

If you want to search for [a-z][1-3] or [0-9][a-z], you would combine them: ([a-z][1-3])|([0-9][a-z]).

Further examples:

[0-9] or \d

Find all files/folders with at least one digit in its name.


Find all files/folders containing "a" or "b" in their name.


Find all files/folders containing at least one character in their name that is not in the range A-Z or a-z.


Find all files/folders which start with an "E" followed by exactly 7 digits.


Find all files/folders with a folder depth of at least 2 and at most 4.


Find all files/folders with invalid ASCII characters.


Find all files/folders with Unicode characters which cannot be printed.


Find all file/Folder names that contain the non-breakable space character (Unicode NOBR, U+00A0) instead of a normal space character.


Find all file and folder names, that contain characters which are invalid on SharePoint servers.

Further information and additional examples can be found here.

A description of all special characters that can be used with regular expression can be found here.

For further help in forming regular expressions following tools can be used: (online) (online) (download) (download) (download)