RegEX Cheat Sheet & Quick Reference

This is a quick cheat sheet to getting started with regular expressions. ... re.compile, Compile a regular expression pattern for later use. RegEXcheatsheetAquickreferenceforregularexpressions(regex),includingsymbols,ranges,grouping,assertionsandsomesamplepatternstogetyoustarted. #GettingStarted #Introduction Thisisaquickcheatsheettogettingstartedwithregularexpressions. RegexinPython(quickref.me) RegexinJavaScript(quickref.me) RegexinPHP(quickref.me) RegexinJava(quickref.me) RegexinMySQL(quickref.me) RegexinVim(quickref.me) RegexinEmacs(quickref.me) Onlineregextester(regex101.com) #CharacterClasses Pattern Description [abc] Asinglecharacterof:a,borc [^abc] Acharacterexcept:a,borc [a-z] Acharacterintherange:a-z [^a-z] Acharacternotintherange:a-z [0-9] Adigitintherange:0-9 [a-zA-Z] Acharacterintherange:a-zorA-Z [a-zA-Z0-9] Acharacterintherange:a-z,A-Zor0-9 #Quantifiers Pattern Description a? Zerooroneofa a* Zeroormoreofa a+ Oneormoreofa [0-9]+ Oneormoreof0-9 a{3} Exactly3ofa a{3,} 3ormoreofa a{3,6} Between3and6ofa a* Greedyquantifier a*? Lazyquantifier a*+ Possessivequantifier #CommonMetacharacters ^ { + < [ * ) > . ( | $ \ ? Escapethesespecialcharacterswith\ #MetaSequences Pattern Description . Anysinglecharacter \s Anywhitespacecharacter \S Anynon-whitespacecharacter \d Anydigit,Sameas[0-9] \D Anynon-digit,Sameas[^0-9] \w Anywordcharacter \W Anynon-wordcharacter \X AnyUnicodesequences,linebreaksincluded \C Matchonedataunit \R Unicodenewlines \v Verticalwhitespacecharacter \V Negationof\v-anythingexceptnewlinesandverticaltabs \h Horizontalwhitespacecharacter \H Negationof\h \K Resetmatch \n Matchnthsubpattern \pX UnicodepropertyX \p{...} Unicodepropertyorscriptcategory \PX Negationof\pX \P{...} Negationof\p \Q...\E Quote;treatasliterals \k Matchsubpatternname \k'name' Matchsubpatternname \k{name} Matchsubpatternname \gn Matchnthsubpattern \g{n} Matchnthsubpattern \g Recursenthcapturegroup \g'n' Recursesnthcapturegroup. \g{-n} Matchnthrelativeprevioussubpattern \g Recursenthrelativeupcomingsubpattern \g'+n' Matchnthrelativeupcomingsubpattern \g'letter' Recursenamedcapturegroupletter \g{letter} Matchpreviously-namedcapturegroupletter \g Recursesnamedcapturegroupletter \xYY HexcharacterYY \x{YYYY} HexcharacterYYYY \ddd Octalcharacterddd \cY ControlcharacterY [\b] Backspacecharacter \ Makesanycharacterliteral #Anchors Pattern Description \G Startofmatch ^ Startofstring $ Endofstring \A Startofstring \Z Endofstring \z Absoluteendofstring \b Awordboundary \B Non-wordboundary #Substitution Pattern Description \0 Completematchcontents \1 Contentsincapturegroup1 $1 Contentsincapturegroup1 ${foo} Contentsincapturegroupfoo \x20 Hexadecimalreplacementvalues \x{06fa} Hexadecimalreplacementvalues \t Tab \r Carriagereturn \n Newline \f Form-feed \U UppercaseTransformation \L LowercaseTransformation \E TerminateanyTransformation #GroupConstructs Pattern Description (...) Captureeverythingenclosed (a|b) Matcheitheraorb (?:...) Matcheverythingenclosed (?>...) Atomicgroup(non-capturing) (?|...) Duplicatesubpatterngroupnumber (?#...) Comment (?'name'...) NamedCapturingGroup (?...) NamedCapturingGroup (?P...) NamedCapturingGroup (?imsxXU) Inlinemodifiers (?(DEFINE)...) Pre-definepatternsbeforeusingthem #Assertions - - (?(1)yes|no) Conditionalstatement (?(R)yes|no) Conditionalstatement (?(R#)yes|no) RecursiveConditionalstatement (?(R&name)yes|no) Conditionalstatement (?(?=...)yes|no) Lookaheadconditional (?(?<=...)yes|no) Lookbehindconditional #Lookarounds - - (?=...) PositiveLookahead (?!...) NegativeLookahead (?<=...) PositiveLookbehind (?name) Recursesubpatternname #POSIXCharacterClasses CharacterClass Sameas Meaning [[:alnum:]] [0-9A-Za-z] Lettersanddigits [[:alpha:]] [A-Za-z] Letters [[:ascii:]] [\x00-\x7F] ASCIIcodes0-127 [[:blank:]] [\t] Spaceortabonly [[:cntrl:]] [\x00-\x1F\x7F] Controlcharacters [[:digit:]] [0-9] Decimaldigits [[:graph:]] [[:alnum:][:punct:]] Visiblecharacters(notspace) [[:lower:]] [a-z] Lowercaseletters [[:print:]] [-~]==[[:graph:]] Visiblecharacters [[:punct:]] [!"#$%&’()*+,-./:;<=>[email protected][]^_`{|}~] Visiblepunctuationcharacters [[:space:]] [\t\n\v\f\r] Whitespace [[:upper:]] [A-Z] Uppercaseletters [[:word:]] [0-9A-Za-z_] Wordcharacters [[:xdigit:]] [0-9A-Fa-f] Hexadecimaldigits [[:<: startofword>:]] [\b(?<=\w)] Endofword #Controlverb - - (*ACCEPT) Controlverb (*FAIL) Controlverb (*MARK:NAME) Controlverb (*COMMIT) Controlverb (*PRUNE) Controlverb (*SKIP) Controlverb (*THEN) Controlverb (*UTF) Patternmodifier (*UTF8) Patternmodifier (*UTF16) Patternmodifier (*UTF32) Patternmodifier (*UCP) Patternmodifier (*CR) Linebreakmodifier (*LF) Linebreakmodifier (*CRLF) Linebreakmodifier (*ANYCRLF) Linebreakmodifier (*ANY) Linebreakmodifier \R Linebreakmodifier (*BSR_ANYCRLF) Linebreakmodifier (*BSR_UNICODE) Linebreakmodifier (*LIMIT_MATCH=x) Regexenginemodifier (*LIMIT_RECURSION=d) Regexenginemodifier (*NO_AUTO_POSSESS) Regexenginemodifier (*NO_START_OPT) Regexenginemodifier #Regexexamples #Characters Pattern Matches ring Matchringspringboardetc. . Matcha,9,+etc. h.o Matchhoo,h2o,h/oetc. ring\? Matchring? \(quiet\) Match(quiet) c:\\windows Matchc:\windows Use\tosearchforthesespecialcharacters:[\^$.|?*+(){} #Alternatives Pattern Matches cat|dog Matchcatordog id|identity Matchidoridentity identity|id Matchidoridentity Orderlongertoshorterwhenalternativesoverlap #Characterclasses Pattern Matches [aeiou] Matchanyvowel [^aeiou] MatchaNONvowel r[iau]ng Matchring,wrangle,sprung,etc. gr[ae]y Matchgrayorgrey [a-zA-Z0-9] Matchanyletterordigit In[]alwaysescape.\]andsometimes^-. #Shorthandclasses Pattern Meaning \w "Word"character(letter,digit,orunderscore) \d Digit \s Whitespace(space,tab,vtab,newline) \W,\D,or\S Notword,digit,orwhitespace [\D\S] Meansnotdigitorwhitespace,bothmatch [^\d\s] Disallowdigitandwhitespace #Occurrences Pattern Matches colou?r Matchcolororcolour [BW]ill[ieamy's]* MatchBill,Willy,William'setc. [a-zA-Z]+ Match1ormoreletters \d{3}-\d{2}-\d{4} MatchaSSN [a-z]\w{1,7} MatchaUWNetID #Greedyversuslazy Pattern Meaning *+{n,}greedy Matchasmuchaspossible <.> Finds1bigmatchinbold *?+?{n,}?lazy Matchaslittleaspossible <.> Finds2matchesinbold #Scope Pattern Meaning \b "Word"edge(nexttonon"word"character) \bring Wordstartswith"ring",exringtone ring\b Wordendswith"ring",exspring \b9\b Matchsingledigit9,not19,91,99,etc.. \b[a-zA-Z]{6}\b Match6-letterwords \B Notwordedge \Bring\B Matchspringsandwringer ^\d*$ Entirestringmustbedigits ^[a-zA-Z]{4,20}$ Stringmusthave4-20letters ^[A-Z] Stringmustbeginwithcapitalletter [\.!?"')]$ Stringmustendwithterminalpuncutation #Modifiers Pattern Meaning (?i)[a-z]*(?-i) IgnorecaseON/OFF (?s).*(?-s) Matchmultiplelines(causes.tomatchnewline) (?m)^.*;$(?-m) ^&$matchlinesnotwholestring (?x) #free-spacingmode,thisEOLcommentignored (?-x) free-spacingmodeOFF /regex/ismx Modifymodeforentirestring #Groups Pattern Meaning (in\|out)put Matchinputoroutput \d{5}(-\d{4})? USzipcode("+4"optional) ParsertriesEACHalternativeifmatchfailsaftergroup. Canleadtocatastrophicbacktracking. #Backreferences Pattern Matches (to)(be)ornot\1\2 Matchtobeornottobe ([^\s])\1{2} Matchnon-space,thensametwicemore aaa,... \b(\w+)\s+\1\b Matchdoubledwords #Non-capturinggroup Pattern Meaning on(?:click\|load) Fasterthan:on(click\|load) Usenon-capturingoratomicgroupswhenpossible #Atomicgroups Pattern Meaning (?>red\|green\|blue) Fasterthannon-capturing (?>id\|identity)\b Matchid,butnotidentity "id"matches,but\bfailsafteratomicgroup, parserdoesn'tbacktrackintogrouptoretry'identity' Ifalternativesoverlap,orderlongertoshorter. #Lookaround Pattern Meaning (?=) Lookahead,ifyoucanfindahead (?!) Lookahead,ifyoucannotfindahead (?<=) Lookbehind,ifyoucanfindbehind (?>>sentence='Thisisasamplestring' >>>bool(re.search(r'this',sentence,flags=re.I)) True >>>bool(re.search(r'xyz',sentence)) False #re.findall() >>>re.findall(r'\bs?pare?\b','parsparapparentsparepartpare') ['par','spar','spare','pare'] >>>re.findall(r'\b0*[1-9]\d{2,}\b','0501035154122698234') ['0501','154','98234'] #re.finditer() >>>m_iter=re.finditer(r'[0-9]+','453496515934204') >>>[m[0]forminm_iterifint(m[0])<350] ['45','349','4','204'] #re.split() >>>re.split(r'\d+','Sample123string42with777numbers') ['Sample','string','with','numbers'] #re.sub() >>>ip_lines="catapults\nconcatenate\ncat" >>>print(re.sub(r'^',r'*',ip_lines,flags=re.M)) *catapults *concatenate *cat #re.compile() >>>pet=re.compile(r'dog') >>>type(pet) >>>bool(pet.search('Theyboughtadog')) True >>>bool(pet.search('Acatcrossedtheirpath')) False #Functions Function Description re.findall Returnsalistcontainingallmatches re.finditer Returnaniterableofmatchobjects(oneforeachmatch) re.search ReturnsaMatchobjectifthereisamatchanywhereinthestring re.split Returnsalistwherethestringhasbeensplitateachmatch re.sub Replacesoneormanymatcheswithastring re.compile Compilearegularexpressionpatternforlateruse re.escape Returnstringwithallnon-alphanumericsbackslashed #Flags - - - re.I re.IGNORECASE Ignorecase re.M re.MULTILINE Multiline re.L re.LOCALE Make\w,\b,\slocaledependent re.S re.DOTALL Dotmatchesall(includingnewline) re.U re.UNICODE Make\w,\b,\d,\sunicodedependent re.X re.VERBOSE Readablestyle #RegexinJavaScript #test() lettextA='IlikeAPPlesverymuch'; lettextB='IlikeAPPles'; letregex=/apples$/i //Output:false console.log(regex.test(textA)); //Output:true console.log(regex.test(textB)); #search() lettext='IlikeAPPlesverymuch'; letregexA=/apples/; letregexB=/apples/i; //Output:-1 console.log(text.search(regexA)); //Output:7 console.log(text.search(regexB)); #exec() lettext='Doyoulikeapples?'; letregex=/apples/; //Output:apples console.log(regex.exec(text)[0]); //Output:Doyoulikeapples? console.log(regex.exec(text).input); #match() lettext='HereareapplesandapPleS'; letregex=/apples/gi; //Output:["apples","apPleS"] console.log(text.match(regex)); #split() lettext='This593stringwillbebrok294enatplaceswhered1gitsare.'; letregex=/\d+/g //Output:["This","stringwillbebrok","enatplaceswhered","gitsare."] console.log(text.split(regex)) #matchAll() letregex=/t(e)(st(\d?))/g; lettext='test1test2'; letarray=[...text.matchAll(regex)]; //Output:["test1","e","st1","1"] console.log(array[0]); //Output:["test2","e","st2","2"] console.log(array[1]); #replace() lettext='DoyoulikeaPPles?'; letregex=/apples/i //Output:Doyoulikemangoes? letresult=text.replace(regex,'mangoes'); console.log(result); #replaceAll() letregex=/apples/gi; lettext='HereareapplesandapPleS'; //Output:Herearemangoesandmangoes letresult=text.replaceAll(regex,"mangoes"); console.log(result); #RegexinPHP #Functions - - preg_match() Performsaregexmatch preg_match_all() Performaglobalregularexpressionmatch preg_replace_callback() Performaregularexpressionsearchandreplaceusingacallback preg_replace() Performaregularexpressionsearchandreplace preg_split() Splitsastringbyregexpattern preg_grep() Returnsarrayentriesthatmatchapattern #preg_replace $str="VisitMicrosoft!"; $regex="/microsoft/i"; //Output:VisitQuickRef! echopreg_replace($regex,"QuickRef",$str); #preg_match $str="VisitQuickRef"; $regex="#quickref#i"; //Output:1 echopreg_match($regex,$str); #preg_matchall $regex="/[a-zA-Z]+(\d+)/"; $input_str="June24,August13,andDecember30"; if(preg_match_all($regex,$input_str,$matches_out)){ //Output:2 echocount($matches_out); //Output:3 echocount($matches_out[0]); //Output:Array("June24","August13","December30") print_r($matches_out[0]); //Output:Array("24","13","30") print_r($matches_out[1]); } #preg_grep $arr=["Jane","jane","Joan","JANE"]; $regex="/Jane/"; //Output:Jane echopreg_grep($regex,$arr); #preg_split $str="Jane\tKate\nLucyMarion"; $regex="@\[email protected]"; //Output:Array("Jane","Kate","Lucy","Marion") print_r(preg_split($regex,$str)); #RegexinJava #Styles #Firstway Patternp=Pattern.compile(".s",Pattern.CASE_INSENSITIVE); Matcherm=p.matcher("aS"); booleans1=m.matches(); System.out.println(s1);//Outputs:true #Secondway booleans2=Pattern.compile("[0-9]+").matcher("123").matches(); System.out.println(s2);//Outputs:true #Thirdway booleans3=Pattern.matches(".s","XXXX"); System.out.println(s3);//Outputs:false #PatternFields - - CANON_EQ Canonicalequivalence CASE_INSENSITIVE Case-insensitivematching COMMENTS Permitswhitespaceandcomments DOTALL Dotallmode MULTILINE Multilinemode UNICODE_CASE Unicode-awarecasefolding UNIX_LINES Unixlinesmode #Methods #Pattern Patterncompile(Stringregex[,intflags]) booleanmatches([Stringregex,]CharSequenceinput) String[]split(Stringregex[,intlimit]) Stringquote(Strings) #Matcher intstart([intgroup|Stringname]) intend([intgroup|Stringname]) booleanfind([intstart]) Stringgroup([intgroup|Stringname]) Matcherreset() #String booleanmatches(Stringregex) StringreplaceAll(Stringregex,Stringreplacement) String[]split(Stringregex[,intlimit]) Therearemoremethods... #Examples Replacesentence: Stringregex="[A-Z\n]{5}$"; Stringstr="IlikeAPP\nLE"; Patternp=Pattern.compile(regex,Pattern.MULTILINE); Matcherm=p.matcher(str); //Outputs:IlikeApple! System.out.println(m.replaceAll("pple!")); Arrayofallmatches: Stringstr="ShesellsseashellsbytheSeashore"; Stringregex="\\w*se\\w*"; Patternp=Pattern.compile(regex,Pattern.CASE_INSENSITIVE); Matcherm=p.matcher(str); Listmatches=newArrayList<>(); while(m.find()){ matches.add(m.group()); } //Outputs:[sells,seashells,Seashore] System.out.println(matches); #RegexinMySQL #Functions Name Description REGEXP Whetherstringmatchesregex REGEXP_INSTR() Startingindexofsubstringmatchingregex(NOTE:OnlyMySQL8.0+) REGEXP_LIKE() Whetherstringmatchesregex(NOTE:OnlyMySQL8.0+) REGEXP_REPLACE() Replacesubstringsmatchingregex(NOTE:OnlyMySQL8.0+) REGEXP_SUBSTR() Returnsubstringmatchingregex(NOTE:OnlyMySQL8.0+) #REGEXP exprREGEXPpat #Examples mysql>SELECT'abc'REGEXP'^[a-d]'; 1 mysql>SELECTnameFROMcitiesWHEREnameREGEXP'^A'; mysql>SELECTnameFROMcitiesWHEREnameNOTREGEXP'^A'; mysql>SELECTnameFROMcitiesWHEREnameREGEXP'A|B|R'; mysql>SELECT'a'REGEXP'A','a'REGEXPBINARY'A'; 10 #REGEXP_REPLACE REGEXP_REPLACE(expr,pat,repl[,pos[,occurrence[,match_type]]]) #Examples mysql>SELECTREGEXP_REPLACE('abc','b','X'); aXc mysql>SELECTREGEXP_REPLACE('abcghi','[a-z]+','X',1,2); abcX #REGEXP_SUBSTR REGEXP_SUBSTR(expr,pat[,pos[,occurrence[,match_type]]]) #Examples mysql>SELECTREGEXP_SUBSTR('abcdefghi','[a-z]+'); abc mysql>SELECTREGEXP_SUBSTR('abcdefghi','[a-z]+',1,3); ghi #REGEXP_LIKE REGEXP_LIKE(expr,pat[,match_type]) #Examples mysql>SELECTregexp_like('aba','b+') 1 mysql>SELECTregexp_like('aba','b{2}') 0 mysql>#i:case-insensitive mysql>SELECTregexp_like('Abba','ABBA','i'); 1 mysql>#m:multi-line mysql>SELECTregexp_like('a\nb\nc','^b$','m'); 1 #REGEXP_INSTR REGEXP_INSTR(expr,pat[,pos[,occurrence[,return_option[,match_type]]]]) #Examples mysql>SELECTregexp_instr('aaaaaaaaa','a{3}'); 2 mysql>SELECTregexp_instr('abba','b{2}',2); 2 mysql>SELECTregexp_instr('abbabba','b{2}',1,2); 5 mysql>SELECTregexp_instr('abbabba','b{2}',1,3,1); 7 Cancel