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Regular Expressions Cheat Sheet

(Taken from and modified to fit on one page, at least in Opera 8. Ow, and damn you for blogmarking this, Mathias! ;] Can't. Handle. The. Requests.)

^ The pattern has to appear at the beginning of a string. ^cat matches any string that begins with cat
$ The pattern has to appear at the end of a string. cat$ matches any string that ends with cat
. Matches any character. cat. matches catT and cat2 but not catty
[] Bracket expression. Matches one of any characters enclosed. gr[ae]y matches gray or grey
[^] Negates a bracket expression. Matches one of any characters EXCEPT those enclosed. 1[^02] matches 13 but not 10 or 12
[-] Range. Matches any characters within the range. [1-9] matches any single digit EXCEPT 0
? Preceeding item must match one or zero times. colou?r matches color or colour but not colouur
+ Preceeding item must match one or more times. be+ matches be or bee but not b
* Preceeding item must match zero or more times. be* matches b or be or beeeeeeeeee
() Parentheses. Creates a substring or item that metacharacters can be applied to a(bee)?t matches at or abeet but not abet
{n} Bound. Specifies exact number of times for the preceeding item to match. [0-9]{3} matches any three digits
{n,} Bound. Specifies minimum number of times for the preceeding item to match. [0-9]{3,} matches any three or more digits
{n,m} Bound. Specifies minimum and maximum number of times for the preceeding item to match. [0-9]{3,5} matches any three, four, or five digits
| Alternation. One of the alternatives has to match. July (first|1st|1) will match July 1st but not July 2

POSIX Character Classes

[:alnum:] alphanumeric character [[:alnum:]]{3} matches any three letters or numbers, like 7Ds
[:alpha:] alphabetic character, any case [[:alpha:]]{5} matches five alphabetic characters, any case, like aBcDe
[:blank:] space and tab [[:blank:]]{3,5} matches any three, four, or five spaces and tabs
[:digit:] digits [[:digit:]]{3,5} matches any three, four, or five digits, like 3, 05, 489
[:lower:] lowercase alphabetics [[:lower:]] matches a but not A
[:punct:] punctuation characters [[:punct:]] matches ! or . or , but not a or 3
[:space:] all whitespace characters, including newline and carriage return [[:space:]] matches any space, tab, newline, or carriage return
[:upper:] uppercase alphabetics [[:upper:]] matches A but not a

Perl-Style Metacharacters

// Default delimiters for pattern /colou?r/ matches color or colour
i Append to pattern to specify a case insensitive match /colou?r/i matches COLOR or Colour
\b A word boundary, the spot between word (\w) and non-word (\W) characters /\bfred\b/i matches Fred but not Alfred or Frederick
\B A non-word boundary /fred\B/i matches Frederick but not Fred
\d A single digit character /a\db/i matches a2b but not acb
\D A single non-digit character /a\Db/i matches aCb but not a2b
\n The newline character. (ASCII 10) /\n/ matches a newline
\r The carriage return character. (ASCII 13) /\r/ matches a carriage return
\s A single whitespace character /a\sb/ matches a b but not ab
\S A single non-whitespace character /a\Sb/ matches a2b but not a b
\t The tab character. (ASCII 9) /\t/ matches a tab.
\w A single word character - alphanumeric and underscore /\w/ matches 1 or _ but not ?
\W A single non-word character /a\Wb/i matches a!b but not a2b



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Vol 25, No.12 (December, 2013) Rational Fools vs. Efficient Crooks The efficient markets hypothesis : Political Skeptic Bulletin, 2013 : Unemployment Bulletin, 2010 :  Vol 23, No.10 (October, 2011) An observation about corporate security departments : Slightly Skeptical Euromaydan Chronicles, June 2014 : Greenspan legacy bulletin, 2008 : Vol 25, No.10 (October, 2013) Cryptolocker Trojan (Win32/Crilock.A) : Vol 25, No.08 (August, 2013) Cloud providers as intelligence collection hubs : Financial Humor Bulletin, 2010 : Inequality Bulletin, 2009 : Financial Humor Bulletin, 2008 : Copyleft Problems Bulletin, 2004 : Financial Humor Bulletin, 2011 : Energy Bulletin, 2010 : Malware Protection Bulletin, 2010 : Vol 26, No.1 (January, 2013) Object-Oriented Cult : Political Skeptic Bulletin, 2011 : Vol 23, No.11 (November, 2011) Softpanorama classification of sysadmin horror stories : Vol 25, No.05 (May, 2013) Corporate bullshit as a communication method  : Vol 25, No.06 (June, 2013) A Note on the Relationship of Brooks Law and Conway Law


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Classic books:

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The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D

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Last modified: March 12, 2019