This question already has an answer here:
Reference - What does this regex mean?
(1 answer)
Closed 5 years ago.
Test String -
COAW983742892 COBW98374289
Regular Expression -
^(COBW|COaW|COXW)[0-9]+
Matching String is -
COAW983742892
My question is , why it don't match the both strings?
Your regex suggests that it should be the start of the String with ^ symbol at the start of regex.
Try this regex -
(COBW|COAW|COXW)[0-9]+
It will match both the strings.
You started your regex from ^ (the start of the string), so the only content
likely to be matched is the initial part of your source string.
Remove the starting ^ from the regex and it will match both substrings.
I assume that:
you use g option,
the true content of your regex is COAW (you changed A into a by mistake),
otherwise set i option.
Related
This question already has answers here:
Regex: match everything but a specific pattern
(6 answers)
Closed 2 years ago.
Hey I have a list of files
B123245.xml
B123245-ext.xml
1234W01.xml
1234W01-ext.xml
Now I need a regular expression filter only the files without -ext in the name.
I tried already this ^.+(?!-ext)\.xml$
but it is not working.
What am I doing wrong?
Not sure about your exact needs, but if you want to exclude those file where "-ext" is right before the xml extension I think you could use:
^.+(?<!-ext)\.xml$
See the demo
^ - Start string anchor.
.+ - 1+ character apart from newline.
(?<!-ext) - A negative lookbehind to assert position isn't preceded by "-ext".
\.xml - Match a literal dot and "xml".
$ - End string anchor.
With the help of user 'The fourth bird' I found out the correct structure.
Here is the correct result
^(?!.*-ext).+\.xml$
This question already has answers here:
Regular expression to match a line that doesn't contain a word
(34 answers)
Closed 2 years ago.
I would like to come out with a regex expression that negate the matched results of regex expression: .google.*search. And, is it possible to achieve it with regex from the regex expression I am trying to negate?
Test data
[1] https://www.google.com/search?newwindow=1&sxsrf=ALeKk02MzEfbUp3jO4Np
[2] https://github.com/redis/redis-rb
[3] https://web.whatsapp.com/
Expected result
Row 2, 3 match the regex pattern and are part of the results.
the following regex does the trick
^(?!.+google.*search)
basically matching the beginning of the line then negating (?!) (negative lookahead) your regex.
You may use a negative lookahead here:
https?:\/\/(?!.*\.google\..*search).*
Demo
The "secret sauce" here is (?!.*\.google\..*search), which asserts that .google. followed by search does not occur anywhere within the URL to the right of the https:// portion.
This question already has an answer here:
Finding the indexes of multiple/overlapping matching substrings
(1 answer)
Closed 7 years ago.
I'm trying to find all matches of a particular pattern "8ab|ab8" in the string "8ab8". So I tried the R command gregexpr("8ab|ab8","8ab8") hoping to get a return vector with the starting positions as c(1,2).
Unfortunately, it seems that what happens is that once the first pattern is matched, that portion of the string is "removed" and the second pattern won't be matched.
For example, once "8ab" is matched, "8ab8" becomes "8" and when R tries matching "ab8" in "8", the pattern won't be found. I know this because gregexpr("8ab|ab8","8ab ab8") works fine and returns starting positions of pattern matches as c(1,5).
The question is, how do I match the same pattern multiple times in the first case?
Use perl regular expressions: perl=TRUE . (see ?regex for info on perl regular expressions)
gregexpr("(?=8ab)|(?=ab8)","8ab8",perl=T)
This question already has an answer here:
Reference - What does this regex mean?
(1 answer)
Closed 8 years ago.
What is the use of
?=
in perl regex
please tell the exact meaning and give some regex example.
(?=...)
is a positive lookahead, a type of zero-width assertion. What it's saying is that the match must be followed by whatever is within the parentheses but that part isn't captured.
Example:
.*(?=bar)
This pattern matches all the characters upto the string bar. When bar is detected then it stops matching. If a line contains more than one bar means it matches upto the last bar because .* does a greedy match.
DEMO
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Regular expression to match string not containing a word?
How can I invert a regular expression in JavaScript?
Say I have the regex foo123. How do I match everything that is not foo123?
Use negative lookahead for this.
(?!foo123).+
matches any string except foo123
If you want to match empty string also, use (?!foo123).*
In your case (according to the comment) the required regex is (?!P[0-9]{1,}).+.
It matches P and 123, but not P123.