Regex repeat twice The simplest answer is Regex repeating a capturing group not returning the last one Hot Network Questions Which other model is being used after one hits ChatGPT free plan's max hit rate? I want to match on strings that are made up of a repeating substring, like how 'foofoo' is 'foo' repeated twice, or 'ababab' is 'ab' repeated three times. " Dec 29, 2012 · Taken literally, "characters repeated more than twice" means that ppp would still be ok because p is repeated exactly twice – JJJ Commented Dec 29, 2012 at 15:37 Jun 3, 2009 · Just to add a note to the (correct) answer from RichieHindle: Note that while Python's regexp implementation (and many others, such as Perl's) can do this, this is no longer a regular expression in the narrow sense of the word. The (?<!\|) is a negative lookbehind that asserts that the last character is not a | . )\1{9,}/ Jun 13, 2021 · Test sample: This is a test 234. RegExp repeated groups. I'm going to assume that the dialect of regular expression treats {} and as metacharacters for counting and grouping, and includes + for one-or-more. ) match and Apr 5, 2017 · Regular expression to match repeated strings. Nov 15, 2017 · Turn the capturing group to non-capturing group and add a \| at the last in your regex. . So say I hade the following string . Match an arbitrary sequence that is repeated twice in a [xyz] called bracket expressions is to match one character within a set. RegEx Repeating Capture Group. (?: ) is called non-capturing group. Here's a regular expression that matches a comma-separated sequence of atoms, where each atom is four alphanumeric characters: Feb 12, 2017 · It's a simple question about regular expressions, but I'm not finding the answer. * Which in a Java string should be ". The words which match will be captured in group 1. + 1 to any number of times. regex. So, you could do: Jul 21, 2022 · How can we reduce a string like haaaaaaapppppyyyyyy to haappyy Such that repetition is allowed to a maximum of twice in a row for a character in a string? including any character ( special characters Mar 25, 2015 · Most regular expression engines expose some way to make your expression global. Try Teams for free Explore Teams Apr 18, 2017 · Regex doesn't support what you're trying to do. I am trying re. When the engine enters the capturing group a second time, it overwrites what it had captured the first time. This is easy to understand if we look at how the regex engine applies ! Compose a regular expression that will match a character appearing between two and five times in succession. Not have to repeat the pattern because it's length becomes a problem (currently, Notepad++ only allows 2047 characters in the search box when using regex and I'm easily going over this limit) Jun 29, 2018 · In text editors, and in languages with no regex method that allows fetching multiple regex matches, the above solution does not work. Dec 5, 2014 · With regular expressions, you can require a pattern be repeated a specific number of times with the {} characters. language-agnostic: Why do some regex engines match . Nov 7, 2020 · How do I repeat the same word two or more times in a row with possible varying intervening whitespace? This is what I tried: e = "bored bored boredbored" if re. Demo on Nov 11, 2013 · I need a regular expression to avoid having the same character(@ is the character) twice consecutively but can have them at muliple places. ' One of my input supplies is feeding me names where the name is repeated two times with a space in between. You might want to include "$", which means "end of the line", to be sure that the line must all consist of allowed triples. Jan 10, 2012 · Well your examples and your text do not match. Like 1 is not repeated, but 2 is mentioned twice, and 3 is 3 times. * See the regex demo. Eg: [0-9]{1} this means 1 digit(0-9) [0-9]+ this means at See full list on upskilld. When this regex matches !abc123!, the capturing group stores only 123. e. NET, Rust. " --> here I need the regex to check if "link" appears twice. *\w*); This is the regular expression (shortened) A repeated capturing group will only capture the last iteration. 0. This can be useful in finding the duplicate characters in a string. replace('--', '-') gives '---' rather than '--') I wrote a function that loops over the characters and does everything in one go (although I'm concerned that using the Sep 2, 2016 · Ask questions, find answers and collaborate at work with Stack Overflow for Teams. In PCRE (PHP): ((?:\w+)+),? Match 1, Group 1. )\\1{2,}", "\\1", F) [1] "happy birthday" Explanation of regex: (. If it's not equal then you can use the regular expression ^([a-zA-Z0-9])\1{17}$ for A LOT more readability. Put a capturing group around the repeated group to capture all iterations or use a non-capturing group instead if you're not interested in the data When it is necessary to specify the minimum and maximum number of repeats explicitly, the bounds operator {} may be used. regex101: Repeating letters more than once Regular Expressions 101 Dec 15, 2011 · Whatever follows after that doesn't really matter to the regex. Details Oct 29, 2012 · I have a Python question imagine variable x below. findall will return the captured characters if there any capturing group else it would return all the matched characters. e. Nov 17, 2014 · This entire group can be repeated one or more times (indicated by the +). sed repeat string on every line. What syntax can I use? \\d{wha To paint a picture, my pattern looks similar to this (pseudo regex pattern) (PAT),(PAT), ,(PAT) Where PAT is some lengthy pattern. Regular Expressions are one of many Formal Languages out there. For example, the entirety of the following lines should Dec 14, 2007 · Here we create a string of three name-value pairs. since your regex contain one greedy capturing group, it captures only the last repeat but matches all the previous repeats. util. *(. I need to do a search that will return the files that have a given string twice. 4. NET regular expressions to detect cases where a string has 5 or more characters and the only character in the string is the same. This is your regular expression without the /g flag, while this is what happens when you apply said flag. Another option is to write some code to use the regex to find a looser pattern but then validate the pattern that you wish to have: Oct 10, 2018 · To disallow four or more consecutive chars in the string, you need ^(?!. *: re. $ asserts position at the end of the string. +?\1){3,}/s Jul 4, 2022 · I suspect that a python regular expression alone will not meet your needs. However in the current form your regex would also demand that the last triple ends in a comma, so you should explicitly code that it's not so. Modified 7 years, 8 months ago. You should probably save the string, lowercase it then compare it to '*all'. *)\1+$", string) Starting at the beginning of the string find a some substring that you can repeat until the end of the string. With this I can check if the word link even appears but Sep 4, 2012 · On another note I think that using a regular expression here is a bit overkill. X{n}|X{m} This regex would test for X occurring exactly n or m times. whether the given string is a valid CSV for my use-case or not. I am trying to find matches where an alphanumeric character is repeated consecutively. g . Viewed 2k times 1 . 1. foo aefhiuafhiauefheiauh bar. , greatgreat or appleapple. Requirements. If you do not allow an empty string, replace last . replaceAll(regex) makes the same replacement twice; There are several ways to fix the issue: Add anchors on both sides of . In the ideal case I can (a) match hurrhurr and (b) identify the core pattern hurr. string = aaa664 => false, it is because of a. {n} 'n' times. The optional part * is due to that in your pattern you repeat the number 1 or more times. g “HazzzeLLllnut$$$”. (?<refDepVal>. For example: someword@someword is ok someword@@someword is not ok someword@someword@someword is ok too. A regular expression that characters repeated more than a specified number of times (9 times in this example). I have no idea if this is possible with regular expressions. Nov 14, 2015 · Now I wonder if I can somehow find words based on repeated patterns (of sizes, say, 2-4) without knowing the individual pattern. Consider the following regular expression, where X is any regex. In order to ensure that a character is repeated exactly twice will require a negative look behind assertion, and such assertions cannot contain group references. 23423 What I have which works: \d{3}. a number where not all digits are the same (except if the entire number is simply a digit): Jul 25, 2021 · Reading the above regex literally, it says: 'Find one-or-more digits followed by an optional (zero-or-one) dash-one-or-more digits, followed by either a comma or end-of-line ($$), the entire preceding pattern repeated one-or-more times. Mar 8, 2011 · I am ignoring group-capturing challenges and treating this as only a validation problem i. 990*2334 sample 123. I understand that the caret ^ in square brackets May 7, 2014 · How to write repeating Regex pattern in JavaScript. but it is wrong because it only checks for single char, not one word. It's basically just matching a certain pattern 12 or 13 times. )\1{3,}). The 1 time you already have in the capture group. For your example, you can use the following to match the same uppercase character five times: blahblah([A-Z])\1{4} Note that to match the regex n times, you need to use \1{n-1} since one match will come from the capture group. string = 12345 => true; string = 11145 => false, because we do not allow any character appear consecutively, this example is the 1. *\1. Nov 6, 2024 · When creating a regular expression that needs a capturing group to grab part of the text matched, a common mistake is to repeat the capturing group instead of capturing a repeated group. How to validate a password using regex so that tho neighbor characters are not identical and a character does not repeat more that twice? Jan 1, 2022 · I'm trying to write a regex that can match ONLY those lines where every white-space separated token occurs exactly twice, regardless of order. Jan 13, 2021 · It's unclear from your example if you want to match always 4 sets of digits separated by a comma or dot, or a variable sets of digits. \d{3}. "aaargh", "arrrrrgh", "yesssssss")? I read the solution for Python, PHP and PCRE on Stack Overflow, but they don't s Apr 28, 2012 · Regular Expression - Repeating Groups. The strings should select out (1) allochirally -----> first 3 characters 'all' repeated twice in string (2) froufrou-----> first 4 characters 'frou' repeated twice in string Apr 17, 2016 · You need a word which is repeated twice OR thrice, thus, \w+ will match all the words; followed by a space \s; but you want exact word repeated previously, so you wrap the already written \w within a to group it - so it becomes (\w+)\s; you now back reference the above and it becomes (\w+)\s\1. It can be boiled down to something as simple as the following. X{n} X, exactly n times X{n,} X, at least n times X{n,m} X, at least n but not more than m times Jul 8, 2016 · What is the Regex to match any character repeated three or more times in R (e. I wrote the following regular expression but on regex101. * twice in a single input string? java: String. Here is how far i got. E. I'm trying to use . It cannot do every thing as it is limited. group(1) this is what I thought, but this just gives me a return of patterns. Is there a regex quantifier that can test for an occurrence X Dec 2, 2021 · You can use a capture group for a single digit ([1-9]) and optionally repeat a backreference \1* containing the same value as the group. match("^(. This global flag is usually denoted with the /g marker at the end of your expression. See here I think that the problem is that you are trying to use repeating capture groups as something to iterate through - like a foreach loop. *(\d)\1{3}. +. Sep 12, 2017 · You do not need the full power of backreferences for this specific case of one character repeats. This is not a beginner's regular expression. This is my first time trying regex and I only understood the grouping so far like \b(link)\b. I could not find any way to do this, after hours of trying I am posting it here to see if anyone can help. You say it cannot repeat more than 3 times. From java. (has_repeating(string))) I personally consider the above to be orders of magnitude easier to read than one complex regular expression. Here's an example of matching a pair of HTML start and end tags (from the link given earlier): Jun 23, 2015 · So I'm trying to put a filter on my server that will scan a slash followed by 30-50 alphanumeric characters, which will then repeat at least 3 times. Thus. The sentence goes: "This link is invalid. Regular expression to match any character being repeated more than 10 times (8 answers) Closed 8 years ago . Jul 12, 2012 · In most regex implementations, you can accomplish this by referencing a capture group in your regex. I want to write a regular expression that helps me finds any repeating single digits. Ask Question Regular expression capturing entire match consisting of repeated groups. /(\b\w+\b). *\1', x). May 17, 2015 · Regular expression that matches any string parenthesized n times. You can have as many groups as you want. I'm having to parse a text dump of a spreadsheet. If exactly 4 sets of digits use this: May 29, 2009 · You need backreferences. A generated password can have, for example, 6 characters. Put a capturing group around the repeated group to capture all iterations or use a non-capturing group instead if you're not interested in the data. Spread 'sed' command over multiple lines. That is not something that regex does. search(r"{}\\s*s/& Sep 20, 2022 · Regex Capture a matching group twice. search(r'(\d+). javascript regular expression repeat with group. Plus, adding or removing a rule doesn't make you have to reimplement a complex regular expression (and thus, be required to re-test all possible combinations). The easiest approach is to instead look for all repetitions and simply check their length. Apr 2, 2016 · Using Regular Expression, from any line of input that has at least one word repeated two or more times. The idea is to use a capturing group for the first bit, and then refer back to it when you're trying to match the last bit. I understand that the caret ^ in square brackets I'm having to parse a text dump of a spreadsheet. For ex : "hello" -> false "ohhhhh" -> true "whatsuppp" -> true Jun 25, 2014 · The finite repetition syntax uses {m,n} in place of star/plus/question mark. Dec 14, 2017 · My requirement is to use only Java regular expression to check if a given string contains the same character repeated more than 3 times in continuation within the string. sub("^. Repeat groups in regex replace. Apr 10, 2019 · Try using sub, with the pattern (. Jun 3, 2019 · I now have the matching 1h 30min not always occur on a new line. I want to determine whether a number appears in sequence exactly two or four times. match("(\w)[\\1][\\1]",mystring) but it doesn't seem to work (always returns None). I am trying to say "whatever alphanumeric letter is captured in the parentheses, check if it occurs twice in a row anywhere. 1h 30min: Title - Description Line 1 1h 30min: Title - Description Line 1 - Description Line 2 - Description Line 3 I am facing an issue to find all strings which have first few (>=2) characters repeated twice in a string in R language. * 0 to any number of times. Like the plus, the star and the repetition using curly braces are greedy. *$", "(replacement)", "sample text") Nov 6, 2024 · The reason is that upon recursion, the regex engine takes a fresh start in attempting the whole regex. We will break down the structure and functionality of the regex, explaining each component in detail. Regex repetition group. To match your text requirement, your regex should be. All matches (don't return after first match) m modifier: multi line. Ask Question Asked 7 years, 8 months ago. Jan 7, 2014 · Some of the other answers are repeating the lookahead assertions. I would like to have a regex that only matches, if a certain string is found exactly twice in a particular configuration (text output) I tried matching the corresponding area, set it in a group and then try to rematch the exact same thing with a backtrack:. match(R) returns [“zzz”,“LL”,“ll”,"$$$"] I can’t see how it does this? When I omit the \\1+, so that the expression becomes var R = /[^]/g It matches every individual character in a string. It cannot be used to extract patterns and research the string for the pattern it extracted. I have a regular expression that correctly parses each line of the data, but it's rather long. I wrote the regex pattern and checked its working on regex101. May 3, 2016 · The key distinction is repeating a captured group instead of capturing a repeated group. 12. 3. You could just build the regex that would check for a repeat of every single lower case letter Sep 9, 2013 · Repeating a regex pattern. Jun 24, 2014 · I want regex to match a pattern only when it consists of a repeated subpattern. Pattern:. *" Mar 3, 2019 · It is essentially the same as your regex, looking for a word of 4 characters that is repeated, but it looks for 2 extra occurrences (so it appears 3 times). Jun 28, 2011 · If the regex should be applied to the entire string (as opposed to finding "repeat-numbers in a longer string), use start- and end-of-line anchors instead of \b: ^(\d)\1+$ Edit: How to match the exact opposite, i. If you're using a regular expression system that has a different requirement (\{\}, for example) then adjust accordingly. Here, either x, y or z. In those cases, this kind of regex is used to get the second match: Feb 20, 2017 · For the pattern search, you cannot do this with regex, because regex is to search patterns you know they exist. For example, hurrhurr contains hurr as repeated pattern. {n,} at-least 'n' times. Aug 3, 2011 · If I have a set of characters like "abcdefghij" and using this characters, I generate random a password using this characters. 2. May 12, 2016 · Put the regEx block in and add * or +. Non-capturing parentheses group the regex so that you can apply regex operators, but do not capture anything. … - Selection from Regular Expressions Cookbook, 2nd Edition [Book] Regular expression tester with syntax highlighting, explanation, cheat sheet for PHP/PCRE, Python, GO, JavaScript, Java, C#/. The regex includes a negative lookahead for 3 repeats, so that it won't match the same word twice if it occurs 4 or more times. All quantifiers and alternatives behave as if the matching process prior to the recursion had never happened at all, other than that the engine advanced through the string. Feb 16, 2019 · This is a common regex issue, it affects a lot of regex flavors, see related. The pattern I want to repeat is \s+(\w*\. *(\\d)\\1{3}. Repeat Part of the Regex a Certain Number of Times Problem Create regular expressions that match the following kinds of numbers: A googol (a decimal number with 100 digits). So I don't want to Mar 19, 2012 · While matching an email address, after I match something like yasar@webmail, I want to capture one or more of (\\. 12. Cher Cher; Humphrey Bogart Humphrey Bogart; Edgar Allen Poe Edgar Allen Poe; Is there a regular expression that I can use to find the lines with the repeats? And get it to give me the name (un-repeated). So for example, if I have a document littered with horizontal lines: ===== I'm a regular expression newbie and I can't quite figure out how to write a single regular expression that would "match" any duplicate consecutive words such as: Paris in the the spring. 5. Capturing a repeated group captures all iterations. Currently my code, in Python, looks like this: re. So, you could do: Jul 21, 2022 · How can we reduce a string like haaaaaaapppppyyyyyy to haappyy Such that repetition is allowed to a maximum of twice in a row for a character in a string? including any character ( special characters Sep 2, 2016 · Ask questions, find answers and collaborate at work with Stack Overflow for Teams. 0-5 HELLO Match 2, Group 1. Refining a regex repeating group. x='1234328732'#a string of digits re. Oct 11, 2013 · How do I print the number of lines in which a string appears 2 or more times using unix grep and regular expressions? 2 Find lines matching a pattern, provided their value in a specified column occurs exactly twice in the input file Aug 14, 2018 · I want to check with regex if the word link appears twice in a sentence. At this stage you have all words which are Jun 26, 2012 · I am trying to write a regular expression that will detect a word that is repeated twice, e. F <- ("hhhappy birthhhhhhdayyy") gsub("(. We then use the pattern above, which will match the entire string, and loop over the matcher for that pattern (which will loop once since our pattern matches the entire string). \d{4} Question 1: Is there a way to simplify it by asking the regex engine to repeat \d{3} twice like Skip to main content I'm looking for a simple regular expression to match the string where no repeated characters. *\w*); This is the regular expression (shortened) Apr 27, 2022 · var R = /([^])\\1+/g I’ve found that this regular expression R is used to match repeating characters in a string. I need regex to do it for both character and digit, please help. [\d] would match either \ or d in POSIX basic regexps, but in perl-compatible regexps, it matches the same as \d alone: a digit. [aA]+[^aA]*[aA]+ Sample strings to Nov 18, 2011 · I am horrible at RegEx expressions and I just don't use them often enough for me to remember the syntax between uses. a{2} is the letter ‘a’ repeated exactly twice, a{2,4} represents the letter ‘a’ repeated between 2 and 4 times, and a{2,} represents the letter ‘a’ repeated at least twice with no upper limit. regular expression nothing to repeat. sed script for duplicating the line ON that same line. Example: JHMCU26809C211501 - good JHMGD18508S219366 - good JHMCU268091111111 - bad 12345678901234567 Mar 21, 2013 · But I want to change the regex pattern, such that it replaces only if the repeating characters repeat more than 3 times. bar jgoeiajgoieajogiae baz. x where x is the same both sides of the dot. If you knew the possibilities then sure you could use a regex (aab#aab|bba#bba). When it matches !123abcabc!, it only stores abc. Causes ^ and $ to match the begin/end of each line (not only begin/end of string) May 13, 2020 · I want to check whether a string includes the letter a (lowercase or uppercase) at least twice. 200. After that, I will present you with two possible solutions. com,I keep getting a "timeout" message, probably because there is a better way to write it: /(\/\w{30,50})(. Expected output: cannot ---> cannot loooooooove ----> love I do not understand the regex r'(\w*)(\w)\2(\w*)' and r'\1\2\3' It would be helpful if the above regexs are interpreted in an understandable way. regex: matching a repeating sequence. That's not necessary. Nov 13, 2021 · If it is greedy, it will first match till the end of the line, and will then backtrack until it can repeat 1 or more times till the end of the string, and for an evenly divided part like this of 4 words, you can capture 2 words and match the same 2 words with the backreference \1 I am using Cisco Prime Infrastrucure, which uses the Java regex engine. As you have already found out, the difference is that repeating a captured group captures only the last iteration. Feb 13, 2013 · Take the following input: foo. This means that your expression will applied multiple times. So, for example, if I was searching on the word "how", then file one would not match: Hello how are you today? Nov 2, 2009 · I'm looking for a simple regular expression to match the same character being repeated more than 10 or so times. May 5, 2015 · I want to have a regex expression do that. I am using grepWin to search my files. Try this: Nov 6, 2024 · This regular expression will indeed match these tags. foo ogiejaogijaeoigjea Say I want to match x. * with . g. Try the link below. Because re. However, it no longer meets our requirement to capture the tag’s label into the capturing group. /(. In this tutorial, we will explore the regular expression pattern ( [^, ]+) (, \1)* (, |$) and learn how it can be used to match repeated words or phrases. *?) g modifier: global. com Nov 6, 2024 · Let’s take a look inside the regex engine to see in detail how this works and why this causes our regex to fail. )\\1{2,}:. com. The regular expression that you wrote will actually match D-1150A, D-1150B and D-1150C. Parentheses in regular expressions do two things; they group together a sequence of items in a regular expression, so that you can apply an operator to an entire sequence instead of just the last item, and they capture the contents of that group so you can extract the substring that was matched by that subexpression in the regex. \\w+)(what I am doing is a little bit more complicated, this is just an example), I t Sep 23, 2021 · As pointed out by Pseudonym (in the comments) it's not a known pattern nor regular to be matched by a simple regex. Now that we’ve learned how to account for uncertainty of the characters that should be matched by a regex, it’s time to focus on how to account for uncertainty in the length of the patterns that we would like to match. I am trying to make a Apr 27, 2022 · var R = /([^])\\1+/g I’ve found that this regular expression R is used to match repeating characters in a string. 000 is a repeat of exactly 3 times so it should be OK, but 0000 is a repeat of 4 which is more than 3 so it should not. Given this text: a a a b b b I want a regex patter Aug 14, 2012 · Given that the regular expressions weren't very good with edge cases (like 5 consecutive delimiters) and I had to deal with replacing the double delimiters with a single one (and then again it would get tricky because '----'. Regular expression tester with syntax highlighting, explanation, cheat sheet for PHP/PCRE, Python, GO, JavaScript, Java, C#/. anfm ypzf xyqly msralx wofan lbxlbh ocsik gqnxrqv adcgx hmcwln