I am trying to capture first occurence of anything that looks like a domain name from a string. For examaple my.domain.home.com from 'dfasdf https://www.my.domain.home.com fadsfas'. I am using \b assertion or non-capturing group (?:www\.) to mark the start of my capturing group. But instead I get www.my.domain.home.com i.e. the www. is not stripped out.
This is my full regex:
\b(?:www\.)((?=[a-z0-9-]{1,63}\.)(xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,63}\b
this is the part that I am unsure of:
\b(?:www\.)
how can I make my capturing start at the beginning of the word OR end of 'www.'?
[CLARIFICATION]
If there is no 'www.' it should capture at the beginning of the word. If there is 'www.' it should start capturing after the dot in 'www.' at the beginning of the possible domain string.
I have checked it with https://www.regex101.com/r/NjR11m/1/tests as well but my final destination is Teradata 15.10 regex which is said to be compliant with the Perl dialect. So if you could help me with in the Perl context I guess I will be fine.
SELECT 'dfasdf https://www.my.domain.home.com fadsfas' AS string,
REGEXP_SUBSTR(string,
'\b(?:www\.)((?=[a-z0-9-]{1,63}\.)(xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,63}\b'
) AS url_to_match;
For 'dfasdf https://my.domain.home.com fadsfas' it should return my.domain.home.com as well.
Additional examples of the strings that should also return my.domain.home.com
'dfasdf my.domain.home.com fadsfas'
'dfasdf ,my.domain.home.com-- fadsfas'
'dfasdf www.my.domain.home.com#fadsfas'
[SOLUTION]
REGEXP_SUBSTR(LOWER(string),
'\b(?!www\.)((?=[a-z0-9-]{1,63}\.)(xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,63}\b'
)
The problem with www. being included in the match seems to be because you're using the 0th group (which is the full match, not just the capturing groups). While I don't know how to change that, it is possible to reformulate the regex so that group 0 and group 1 have the same value, like so:
\b(?!www\.)([-a-z0-9]{1,63}(?:\.[-a-z0-9]{1,63})+)
This just says the match can't start at www., rather than allowing the match to start there and then having to ignore it.
I've made a modified version of your regex that shows how it works. Note that if you want to match names with mixed-case alphanumerics you'll need to add A-Z to the a-z0-9, or turn on case-insensitivity; matching non-ascii domain names is more work, and left for the interested reader to work out.
Related
I'd like to find word RADU3_ or RADU3- in a sentence that begins with xlink:href= and ends with .svg
How to do this?
I've tried following, but does not give the result I'm expecting.
(?=\wxlink:href=|\wsvg\b)|\bRADU3_|\bRADU3-
Just last line in example is good result (RADU3_)
ProductionGraphics\GP1**RADU3-**11_HeatingFurnaceF1.svg
PB:ExpressionText id="RADU3_FUEL GAS _SUM_EX" PBD:LinkUses
xlink:href="C:\ProcBookImport\MaintenanceGraphics\RADU3_AI.svg"
Example...
Not sure exactly how you want to use it but the below pattern finds the string. I put the RADU3 part in a group where I matches RADU3 followed by - or _ ([_-])
(xlink:href=.*)(RADU3[_-]*)(.*\.svg)
Edit, handle multiple occurences
If a string might contain the pattern several times then use ? to allow a group to repeat itself
(RADU3[_-]*?)(.*?\.svg?)
The above could be used in a replace expression like
\1someotherword\3
Where \2 is the second group that is replaced
If you want to make sure that the string starts with xlink:href= and ends with \.svg you could use anchors to assert the start ^ and the end $ of the string.
Use 1 capturing group to make sure xlink:href= comes before RADU3 followed by an underscore or a hyphen. Then you could match it and in the replacement use that capturing group follwed by your replacement.
You could use a positive lookahead to assert that the string ends with \.svg
That will match:
^(xlink:href=.*)\bRADU3[_-](?=.*\.svg$)
^ Assert the start of the string
(xlink:href=.*) Capturing group, match up until the last occurence of ..
\bRADU3[_-] Word boundary to prevent matching part of a larger word. Match RADU3 followed by an underscore or hyphen
(?=.*\.svg$) Positive lookahead to assert the string ends with .svg
See the regex demo
It sounds like you only want the word (substring) if it is in a specific context?
In your case, you can restart the regex midways if you want to have starting and ending conditions (multiple conditions) for a string, but at the same time only want to use these conditions as "if-statements" and not as part of the result.
The following uses this method, and utilizes restarts (\K) in order to only extract the substring you are looking for.
# The string has to start with "xlink:href="
xlink:href=
# Fetch everything up to our match, and the restart the regex
.*\K
# The strings we are looking for
(RADU3[-_])
# String has to end with ".svg"
(?=(.*\.svg))
If you want the entire string matching our rules you are looking for something like this:
#The string has to start with "xlink:href"
^(xlink:href=).*
# The strings we are looking for
(RADU3[-_])
# String has to end with ".svg"
(\w+\.svg)
#Get everything after .svg too
.*
If you only want the ending " after the .svg, you'd want to modify the last part where I just take everything after .svg
You can play around with what I have come up with at regex101 (no affiliation, just love their site): https://regex101.com/r/g0v07V/3/
Okay, so the task is that there is a string that can either look like post, or post put or even get put post. All of these must be matched. Preferably deviances like [space]post, or get[space] should not be matched.
Currently I came up with this
^(post|put|delete|get)(( )(post|put|delete|get))*$
However I'm not satisfied with it, because I had to specify (post|put|delete|get) twice. It also matches duplications like post post.
I'd like to somehow use a backreference(?) to the first group so that I don't have to specify the same condition twice.
However, backreference \1 would help me only match post post, for example, and that's the opposite of what I want. I'd like to match a word in the first capture group that was NOT previously found in the string.
Is this even possible? I've been looking through SO questions, but my Google-fu is eluding me.
If you are using a PCRE-based regex engine, you may use subroutine calls like (?n) to recurse the subpatterns.
^(post|put|delete|get)( (?!\1)(?1))*$
^^^^
See the regex demo
Expression details:
^ - start of string
(post|put|delete|get) - Group 1 matching one of the alternatives as literal substrings
( (?!\1)(?1))* - zero or more sequences of:
- a space
(?!\1) - a negative lookahead that fails the match if the text after the current location is identical to the one captured into Group 1 due to backreference \1
(?1) - a subroutine call to the first capture group (i.e. it uses the same pattern used in Group 1)
$ - end of string
UPDATE
In order to avoid matching strings like get post post, you need to also add a negative lookahead into Group 1 so that the subroutine call was aware that we do not want to match the same value that was captured into Group 1.
^((post|put|delete|get)(?!.*\2))( (?1))*$
See the regex demo
The difference is that we capture the alternations into Group 2 and add the negative lookahead (?!.*\2) to disallow any occurrences of the word we captured further in the string. The ( (?1))* remains intact: now, the subroutine recurses the whole Capture Group 1 subpattern with the lookahead.
I'm trying to add another feature to a regex which is trying to validate names (first or last).
At the moment it looks like this:
/^(?!^mr$|^mrs$|^ms$|^miss$|^dr$|^mr-mrs$)([a-z][a-z'-]{1,})$/i
https://regex101.com/r/pQ1tP2/1
The idea is to do the following
Don't allow just adding a title like Mr, Mrs etc
Ensure the first character is a letter
Ensure subsequent characters are either letters, hyphens or apostrophes
Minimum of two characters
I have managed to get this far (shockingly I find regex so confusing lol).
It matches things like O'Brian or Anne-Marie etc and is doing a pretty good job.
My next additions I've struggled with though! trying to add additional features to the regex to not match on the following:
Just entering the same characters i.e. aaa bbbbb etc
Thanks :)
I'd add another negative lookahead alternative matching against ^(.)\1*$, that is, any character, repetead until the end of the string.
Included as is in your regex, it would make that :
/^(?!^mr$|^mrs$|^ms$|^miss$|^dr$|^mr-mrs$|^(.)\1*$)([a-z][a-z'-]{1,})$/i
However, I would probably simplify your negative lookahead as follows :
/^(?!(mr|ms|miss|dr|mr-mrs|(.)\2*)$)([a-z][a-z'-]{1,})$/i
The modifications are as follow :
We're evaluating the lookahead at the start of the string, as indicated by the ^ preceding it : no need to repeat that we match the start of the string in its clauses
Each alternative match the end of the string. We can put the alternatives in a group, which will be followed by the end-of-string anchor
We have created a new group, which we have to take into account in our back-reference : to reference the same group, it now must address \2 rather than \1. An alternative in certain regex flavours would have been to use a non-capturing group (?:...)
I'm trying to match first occurrence of window.location.replace("http://stackoverflow.com") in some HTML string.
Especially I want to capture the URL of the first window.location.replace entry in whole HTML string.
So for capturing URL I formulated this 2 rules:
it should be after this string: window.location.redirect("
it should be before this string ")
To achieve it I think I need to use lookbehind (for 1st rule) and lookahead (for 2nd rule).
I end up with this Regex:
.+(?<=window\.location\.redirect\(\"?=\"\))
It doesn't work. I'm not even sure that it legal to mix both rules like I did.
Can you please help me with translating my rules to Regex? Other ways of doing this (without lookahead(behind)) also appreciated.
The pattern you wrote is really not the one you need as it matches something very different from what you expect: text window.location.redirect("=") in text window.location.redirect("=") something. And it will only work in PCRE/Python if you remove the ? from before \" (as lookbehinds should be fixed-width in PCRE). It will work with ? in .NET regex.
If it is JS, you just cannot use a lookbehind as its regex engine does not support them.
Instead, use a capturing group around the unknown part you want to get:
/window\.location\.redirect\("([^"]*)"\)/
or
/window\.location\.redirect\("(.*?)"\)/
See the regex demo
No /g modifier will allow matching just one, first occurrence. Access the value you need inside Group 1.
The ([^"]*) captures 0+ characters other than a double quote (URLs you need should not have it). If these URLs you have contain a ", you should use the second approach as (.*?) will match any 0+ characters other than a newline up to the first ").
I have a regex
/([/<=][^/]*[/=?])$/g
I'm trying to capture text between the last slashes in a file path
/1/2/test/
but this regex matches "/test/" instead of just test. What am I doing wrong?
You need to use lookaround assertions.
(?<=\/)[^\/]*(?=\/[^\/]*$)
DEMO
or
Use the below regex and then grab the string you want from group index 1.
\/([^\/]*)\/[^\/]*$
The easy way
Match:
every character that is not a "/"
Get what was matched here. This is done by creating a backreference, ie: put inside parenthesis.
followed by "/" and then the end of string $
Code:
([^/]*)/$
Get the text in group(1)
Harder to read, only if you want to avoid groups
Match exactly the same as before, except now we're telling the regex engine not to consume characters when trying to match (2). This is done with a lookahead: (?= ).
Code:
[^/]*(?=/$)
Get what is returned by the match object.
The issue with your code is your opening and closing slashes are part of your capture group.
Demo
text: /1/2/test/
regex: /\/(\[^\/\]*?)(?=\/)/g
captures a list of three: "1", "2", "test"
The language you're using affects the results. For instance, JavaScript might not have certain lookarounds, or may actually capture something in a non-capture group. However, the above should work as intended. In PHP, all / match characters must be escaped (according to regex101.com), which is why the cleaner [/] wasn't used.
If you're only after the last match (i.e., test), you don't need the positive lookahead:
/\/([^\/]*?)\/$/