This question already has answers here:
Regex how to match an optional character
(5 answers)
Closed 5 years ago.
I have a simple Regex that looks for the words "won't connect" in a string.
(.*) won't connect.*
But I want to have it so it can ignore the apostrophe in case the user types in "wont connect".
(.*)won'?t connect.*
should be sufficient, matches " ' " 0 or 1 times
check the demo here
Your pattern:
(.*) won't connect.*
The * quantifier is greedy by default. That means your regex will go wrong with:
foo won't connect won't connect
See demonstration.
If you add a question-mark behind the quantifier, it will be lazy, meaning it will match only as much for the pattern to succeed. See an explanation here.
Improved pattern:
(.*?) won'?t connect.*
Related
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How do I match an entire string with a regex?
(8 answers)
Closed 4 years ago.
I am trying to create a regular expression pattern in C# which allow you to have
next pattern: _DXX at the end of your .
Example :
04R5714A_D15 is correct
04R5714A_D05 is incorrect
04R5714A_D5 is correct
I tried : .*_D([1-9]{1}[0-9]?) but it didn't work :
.*_D[1-9]\d?$ should work for you.
Demo
.* catches everything up until your underscore
_D is a literal match
[1-9] matches one number in that range
\d? matches 0 or 1 single number (0-9)
$ is the end of the string
This question already has answers here:
Regex whitespace word boundary
(3 answers)
Closed 4 years ago.
Regex -> ^([\s]*(?i)(section)[\s]*(?=[xvi])M*D?C{0,4}L?x{0,4}v{0,4}i{0,4})[\s]?
Text -> Section VII, some text.....
This regex matches Section VII and Section VII(space).
But it should not match "Section VII," , as after the match there is one special character.
What you need is a zero-width negative lookahead assertion:
^([\s]*(?i)(section)[\s]*(?=[xvi])M*D?C{0,4}L?x{0,4}v{0,4}i{0,4})(?!\S)
The critical part is (?!\S), which means that no (!) non-whitespace character (\S) should be at the end. It's a zero-width expression, which means that the character itself (if any) won't be a part of your match.
This question already has answers here:
How do I match an entire string with a regex?
(8 answers)
Closed 6 years ago.
I need to detect following format when I enter serial number like
CK123456.789
I used Regex with pattern of
^(CV[0-9]{6}\.[0-9]{3}
to match but if I enter
CK123456.7890
it still able to proceed without flagging error. Is there a better regular expression to detect the trailing 3 digits after '.'?
Depending on how you use the regular expression matcher, you might need to enclose it in ^...$ which forces the pattern to be the whole string, i.e.
^CK[0-9]{6}\.[0-9]{3}$ (Note the CK prefix).
I've also removed your leading (mismatched) parenthesis.
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Reference - What does this regex mean?
(1 answer)
Closed 6 years ago.
I am new to regex. What does regex expression match pattern "\[.*\]" mean?
If I have a text like "Hello [Here]", then success is returned in the match. And match contain [Here].
I read that:
. indicates Any except \n (newline),
* indicates 0 or more times
I don't understand the "\". It believe it is just escape sequence for "\".
So, is the expression "\[.*\]" trying to match a pattern like \[Any text\]?
Yes, you are right. It will match any characters enclosed in []. The .* imply any or no characters enclosed in [].
Also you should try this link which is a very helpful regex tool. You can input the regex pattern and check for matches easily.
I have tried this on regexr, here is a screen shot:
This question already has an answer here:
Reference - What does this regex mean?
(1 answer)
Closed 7 years ago.
I was trying to understand the following regex
^(?!\s)(?!.*\s\s)[ A-Za-z0-9'-]{1,35}(?<!\s)$
Here I understood,
^(?!\s) - (lookahead) means will not match if there is a leading space.
[ A-Za-z0-9'-]{1,35} - will allow A to Z, a to z, 0 to 9, (space), ' and -.
(?<!\s)$ - means will not match if there is a trailing space.
I am unable to understand what this sub-expression is doing?
(?!.*\s\s)
(?!.*\s\s)
means that in the string there should not be 2 adjacent spaces.
.* will scan the string.
\s\s will look for adjacent spaces.?! is negative lookahead so it will break when it finds such a string.See demo.
https://regex101.com/r/eB8xU8/4
I think there is no effect for this lookup.. It will return always true because here you are using greedy search.
It should be
(?!.*?\s\s): which means no two spaces continuous..
.* this is for match everything situation with out looking here and there
.* ? this makes this as a lazy operator and consider situation written at the right side of .*?