2,768 questions
2498
votes
18
answers
1.3m
views
What is a non-capturing group in regular expressions?
How are non-capturing groups, i.e., (?:), used in regular expressions and what are they good for?
- 93.7k
360
votes
3
answers
297k
views
Named regular expression group "(?P<group_name>regexp)": what does "P" stand for?
In Python, the (?P<group_name>…) syntax allows one to refer to the matched string through its name:
>>> import re
>>> match = re.search('(?P<name>.*) (?P<phone>.*)'...
- 95.1k
304
votes
4
answers
156k
views
Python re.sub group: number after \number
How can I replace foobar with foo123bar?
This doesn't work:
>>> re.sub(r'(foo)', r'\1123', 'foobar')
'J3bar'
This works:
>>> re.sub(r'(foo)', r'\1hi', 'foobar')
'foohibar'
- 7,283
260
votes
19
answers
420k
views
RegEx to extract all matches from string using RegExp.exec
I'm trying to parse the following kind of string:
[key:"val" key2:"val2"]
where there are arbitrary key:"val" pairs inside. I want to grab the key name and the value.
For those curious I'm trying to ...
- 2,619
252
votes
32
answers
310k
views
RegEx for matching UK Postcodes
I'm after a regex that will validate a full complex UK postcode only within an input string. All of the uncommon postcode forms must be covered as well as the usual. For instance:
Matches
CW3 9SS
SE5 ...
- 8,940
221
votes
5
answers
186k
views
Vim Regex Capture Groups [bau -> byau : ceu -> cyeu]
I have a list of words:
bau
ceu
diu
fou
gau
I want to turn that list into:
byau
cyeu
dyiu
fyou
gyau
I unsuccessfully tried the command:
:%s/(\w)(\w\w)/\1y\2/g
Given that this doesn't work, what do ...
- 26.5k
193
votes
2
answers
163k
views
Python Regex instantly replace groups
Is there any way to directly replace all groups using regex syntax?
The normal way:
re.match(r"(?:aaa)(_bbb)", string1).group(1)
But I want to achieve something like this:
re.match(r"(\d.*?)\s(\d.*?...
user1467267
166
votes
4
answers
150k
views
Can I use an OR in regex without capturing what's enclosed?
I'm using rubular.com to build my regex, and their documentation describes the following:
(...) Capture everything enclosed
(a|b) a or b
How can I use an OR expression without capturing what's in ...
- 8,006
141
votes
2
answers
253k
views
Regex optional group [duplicate]
I am using this regex:
((?:[a-z][a-z]+))_(\d+)_((?:[a-z][a-z]+)\d+)_(\d{13})
to match strings like this:
SH_6208069141055_BC000388_20110412101855
separating into 4 groups:
SH
6208069141055
...
- 8,704
138
votes
8
answers
180k
views
Can I replace groups in Java regex?
I have this code, and I want to know, if I can replace only groups (not all pattern) in Java regex.
Code:
//...
Pattern p = Pattern.compile("(\\d).*(\\d)");
String input = "6 example input 4";
...
- 1,379
116
votes
1
answer
157k
views
Guide on how to use regex in Nginx location block section?
Nginx regex location syntaxe
Regex expressions can be used with Nginx location block section, this is implemented with the PCRE engine.
What does exactly this feature support as it is not fully ...
- 10k
61
votes
6
answers
21k
views
Negating a backreference in Regular Expressions
if a string has this predicted format:
value = "hello and good morning"
Where the " (quotations) might also be ' (single quote), and the closing char (' or ") will be the same as the opening one. I ...
- 6,160
50
votes
5
answers
93k
views
extract substring using regex in groovy
If I have the following pattern in some text:
def articleContent = "<![CDATA[ Hellow World ]]>"
I would like to extract the "Hellow World" part, so I use the following code to match it:
def ...
- 1,735
46
votes
4
answers
48k
views
preg_replace how to replace only matching xxx($1)yyy pattern inside the selector
I'm trying to use a regular expression to erase only the matching part of an string. I'm using the preg_replace function and have tried to delete the matching text by putting parentheses around the ...
- 2,849
44
votes
3
answers
36k
views
Regular Expression in sed for multiple replacements in one statement
I want to sanitise some input and replace several characters with acceptable input, e.g. a Danish 'å' with 'aa'.
This is easily done using several statements, e.g. /æ/ae/, /å/aa/, /ø/oe/, but due to ...
- 903
39
votes
9
answers
37k
views
How do I write a regular expression that excludes rather than matches, e.g., not (this|string)?
I am stumped trying to create an Emacs regular-expression that excludes groups. [^] excludes individual characters in a set, but I want to exclude specific sequences of characters: something like [^(...
- 51.8k
39
votes
4
answers
16k
views
How do I group regular expressions past the 9th backreference?
Ok so I am trying to group past the 9th backreference in notepad++. The wiki says that I can use group naming to go past the 9th reference. However, I can't seem to get the syntax right to do the ...
- 1,940
30
votes
2
answers
149k
views
Match list of words without the list of chars around
I have this regex
(?:$|^| )(one|common|word|or|another)(?:$|^| )
which matches fine unless the two words are next to each other.
One one's more word'word common word or another word more another
...
- 4,184
28
votes
6
answers
24k
views
Kotlin Regex named groups support
Does Kotlin have support for named regex groups?
Named regex group looks like this: (?<name>...)
- 1,459
26
votes
2
answers
34k
views
Regex and the OR operator without grouping in Python?
Here are the cases. I'm looking for the following pattern in a log file.
All strings are in the form of AB_N or CDE_N.
AB and CDE are fixed letters, followed by an underscore.
N can be either 2 or ...
- 3,117
25
votes
3
answers
5k
views
C++11 regex: digit after capturing group in replacement string
My regex_replace expression uses group $1 right before a '0' character in the replacement string like so:
#include <iostream>
#include <string>
#include <regex>
using namespace std;...
- 4,752
24
votes
3
answers
32k
views
scala regex group matching and replace
val REGEX_OPEN_CURLY_BRACE = """\{""".r
val REGEX_CLOSED_CURLY_BRACE = """\}""".r
val REGEX_INLINE_DOUBLE_QUOTES = """\\\"""".r
val REGEX_NEW_LINE = """\\\n""".r
// Replacing { with '{' and } with '}'...
- 2,715
22
votes
6
answers
46k
views
How can I store captures from a Perl regular expression into separate variables?
I have a regex:
/abc(def)ghi(jkl)mno(pqr)/igs
How would I capture the results of each parentheses into 3 different variables, one for each parentheses? Right now I using one array to capture all the ...
- 1,953
18
votes
5
answers
6k
views
vim yank all matches of regex group into register
I know that I can yank all matched lines into register A like this:
:g/regex/y/A
But I can't seem to figure out how to yank match regex groups into register A:
:g/\(regex\)/\1y A
(E10: \ should be ...
- 865
15
votes
2
answers
7k
views
python regex: duplicate names in named groups
Is there a way to use same name in regex named group in python?
e.g.(?P<n>foo)|(?P<n>bar).
Use case:
I am trying to capture type and id with this regex:
/(?=videos)((?P<type>videos)/...
- 967
14
votes
1
answer
10k
views
Notepad++ regex replace named groups
I try replace author Full name with article title
I have a list of articles, similar like this:
Albershein P., Nevis D. J. A method for analysis of sugars in plant cell wall polysaccharides by ...
- 159
12
votes
3
answers
28k
views
using regex g flag in java
Is it possible to use regex global g flag in java pattern ?
I tried with final Pattern pattern = Pattern.compile(regex,Pattern.DOTALL);
but it do not behave like global flag.
Do we have any ...
- 171
12
votes
1
answer
16k
views
What does ?: in a regular expression mean? [duplicate]
Please explain the meaning of this regular expression and what groups the expression will generate?
$string =~ m/^(\d*)(?: \D.*?)(\d*)$/
PS: I'm re-factoring Perl code to Java.
- 149
11
votes
4
answers
49k
views
Powershell - Regular Expression Multiple Matches
Maybe my reasoning is faulty, but I can't get this working.
Here's my regex: (Device\s#\d(\n.*)*?(?=\n\s*Device\s#|\Z))
Try it: http://regex101.com/r/jQ6uC8/6
$getdevice is the input string. I'm ...
- 336
11
votes
1
answer
20k
views
How golang replace string by regex group? [duplicate]
I want to use regex group to replace string in golang, just like as follow in python:
re.sub(r"(\d.*?)[a-z]+(\d.*?)", r"\1 \2", "123abc123") # python code
So how do I implement this in golang?
- 10.1k
11
votes
7
answers
7k
views
Javascript RegExp non-capturing groups
I am writing a set of RegExps to translate a CSS selector into arrays of ids and classes.
For example, I would like '#foo#bar' to return ['foo', 'bar'].
I have been trying to achieve this with
"#...
- 36.4k
11
votes
3
answers
514
views
how to interpolate string containing capture-group parentheses as regex in Raku?
I want to match against a programmatically-constructed regex, containing a number of (.*) capture groups. I have this regex as a string, say
my $rx = "(.*)a(.*)b(.*)"
I would like to ...
- 1,143
10
votes
1
answer
1k
views
functional difference between lookarounds and non-capture group?
I'm trying to come up with an example where positive look-around works but
non-capture groups won't work, to further understand their usages. The examples I"m coming up with all work with non-...
- 4,551
10
votes
2
answers
12k
views
Groovy: Idiomatic way to replace captured groups
I've a string like this: docker login -u username -p password docker-registry-url.
I execute the command in a Groovy script with execute. For debugging purposes, I print the command before execution, ...
- 25.2k
10
votes
4
answers
497
views
Is it possible to erase a capture group that has already matched, making it non-participating?
In PCRE2 or any other regex engine supporting forward backreferences, is it possible to change a capture group that matched in a previous iteration of a loop into a non-participating capture group (...
- 868
10
votes
2
answers
331
views
Raku regex: How to know which group was captured at an alternation
With perl (and almost any regex flavour), every group is numbered sequentially.
So for example, this code:
'bar' =~ m/(foo)|(bar)/;
print $1 // 'x'; # (1-based index)
print $2 // 'x'; # (1-based ...
- 5,316
10
votes
1
answer
12k
views
Nginx location's regex, is escaping the forward slash needed?
Nginx uses the PCRE engine for evaluating regular expressions, the documentation state that / delimiter is not used so we don’t have to escape the forward slash / in an URI as we may do in a standard ...
- 10k
9
votes
2
answers
11k
views
Firefox gives SyntaxError: invalid regexp group
I have few regular expression used for form validation and I noticed that my project is not accessible through firefox as it shows nothing! but give the error in the console, SyntaxError: invalid ...
- 344
8
votes
2
answers
3k
views
android java regex named groups
I would like to use
matcher.group("login");
In android 8+ on eclipse, but no Matcher.group(String) seems to exist.
Have you got a (built in) solution ?
- 4,265
8
votes
1
answer
2k
views
Regex: Capture one or more groups if exists (Java)
I want to capture groups matching a pattern where the input can contain this group one or more times.
Example:
input = 12361 randomstuff371 12 Mar 16 138more random381 stuff73f
I want to capture the ...
- 99
8
votes
1
answer
506
views
Raku regex: How to use capturing group inside lookaheads
How can I use capturing groups inside lookahead assertion?
This code:
say "ab" ~~ m/(a) <?before (b) > /;
returns:
｢a｣
0 => ｢a｣
But I was expecting to also capture 'b'.
Is there ...
- 5,316
7
votes
4
answers
9k
views
Java Matcher groups: Understanding The difference between "(?:X|Y)" and "(?:X)|(?:Y)"
Can anyone explain:
Why the two patterns used below give different results? (answered below)
Why the 2nd example gives a group count of 1 but says the start
and end of group 1 is -1?
public void ...
- 144
7
votes
2
answers
13k
views
Powershell: Replacing regex named groups with variables
Say I have a regular expression like the following, but I loaded it from a file into a variable $regex, and so have no idea at design time what its contents are, but at runtime I can discover that it ...
- 2,908
7
votes
1
answer
1k
views
Regex named groups in R
For all intents and purposes, I am a Python user and use the Pandas library on a daily basis. The named capture groups in regex is extremely useful. So, for example, it is relatively trivial to ...
- 4,332
7
votes
3
answers
7k
views
Negative lookbehind on a capture group
I'm trying to write some regex that will allow me to do a negative lookbehind on a capture group so that I can extract possible references from emails. I need to know how to look behind from a certain ...
- 75
7
votes
5
answers
2k
views
Find out which group matches in Java regex without linear search?
I have some programmatically assembled huge regex, like this
(A)|(B)|(C)|...
Each sub-pattern is in its capturing group. When I get a match, how do I figure out which group matches without linearly ...
- 3,327
6
votes
3
answers
5k
views
Extract groups matched regex to array in scala
I got this problem. I have a
val line:String = "PE018201804527901"
that matches with this
regex : (.{2})(.{4})(.{9})(.{2})
I need to extract each group from the regex to an Array.
The result ...
- 145
6
votes
2
answers
3k
views
Convert regex Captures into HashMap in Rust?
I have a Regex with an unknown number of named groups with unknown names. I want to match a string to that regex, and get a HashMap<&str, &str> with the name of the groups as key and the ...
- 8,663
6
votes
3
answers
751
views
replace number greater than 5 digits in a text
a <- c("this is a number 9999333333 and i got 12344")
How could i replace the number greater than 5 digits with the extra digits being "X"
Expected Output:
"this is a ...
- 1,073
6
votes
2
answers
1k
views
Remove spaces between single character in string
I was trying to remove duplicate words from a string in scala.
I wrote a udf(code below) to remove duplicate words from string:
val de_duplicate: UserDefinedFunction = udf ((value: String) => {
...
- 338