How to get last word inside slashes using Regular Expressions - regex

How to get last word inside slashes using Regular Expressions in a URL?
Example : http://aaa/bbb/ccc/ddd.aspx returns ccc.


Something like this
/([^/]+)/[^/]*$
Should match the last section of your URL and store ccc in a group.


Using lookbehind and lookahead, this should work
(?<=/)[^/]+(?=/[^/]*$)
(?<=/) the match must be preceeded by /
[^/]+ this will capture everything except a / - as many as possible.
(?=/[^/]*$) the match must be followed by a /, any number of non-slashes, and the end of string.

Related

Regular expression to exactly match the last path segment of an URL without parameters, except if the path ends with a trailing slash

The goal of my regular expression adventure is to create a matcher for a mechanism that could add a trailing slash to URLs, even in the presence of parameters denoted by # or ? at the end of the URL.
For any of the following URLs, I'm looking for a match for segment as follows:
https://example.com/what-not/segment matches segment
https://example.com/what-not/segment?a=b matches segment
https://example.com/what-not/segment#a matches segment
In case there is a match for segment, I'm going to replace it with segment/.
For any of the following URLs, there should be no match:
https://example.com/what-not/segment/ no match
https://example.com/what-not/segment/?a=b no match
https://example.com/what-not/segment/#a no match
because here, there is already a trailing slash.
I've tried:
This primitive regex and their variants: .*\/([^?#\/]+). However, with this approach, I could not make it not match when there is already a trailing slash.
I experimented with negative lookaheads as follows: ([^\/\#\?]+)(?!(.*[\#\?].*))$. In this case, I could not get rid of any ? or # parts properly.
Thank you for your kind help!

Lookahead and lookbehind conditionals are so powerful!
(?<=\/)[\w]+(?(?=[\?\#])|$)
P.s: I just added [\w]+ that means [a-zA-Z0-9_]+.
Of course URLs can contain many other character like - or ~ but for the examples provided it works nicely.

If you want to match urls, you might use
\b(https?://\S+/)[^\s?#/]+(?![^\s?#])
Explanation
\b A word boundary to prevent a partial word match
( Capture group 1
https?://\S+/ Match the protocol, 1+ non whitespace chars and then the last occurrence of /
) Close group 1
[^\s?#/]+ Match 1+ chars other than a whitespace char ? # /
(?![^\s?#]) Negative lookahead, assert that directly to the right is not a non whitespace char other than ? or #
See a regex demo.
In the replacement use group 1 followed by segment/
For a match only instead of a capture group:
(?<=\bhttps?://\S+/)[^\s?#/]+(?![^\s?#])
See another regex demo.

How to match a word based on slash in regular expression

I am trying to match a word with regex. for example, I want to match only first 2 folders in below string
/folder1/folder2/filder3/folder4/folder5
I wrote a below regex to match first two folders but it matches everything till /folder5 but I wanted to match only till /folder2
/(\w.+){2}
I guess .+ matches everything. Any idea how to handle this?

You can use
^/[^/]+/[^/]+
^(?:/[^/]+){2}
Or, if you need to escape slashes:
^\/[^\/]+\/[^\/]+
^(?:\/[^\/]+){2}
See the regex demo. [^/] is a negated character class that matches any char other than a / char.

How to extract only filenames from an URL with RegEx even with ANSI escaped characters?

I need to extract ONLY the file names from any URL. I looked at all previous answers on stackoverflow regarding URLs and filenames, but no one considered the case of a file name with escaped characters.
I have for example an URL like this:
https://content.com/pbpython.py/notebooks/thirsty-allies.mov?file=The%20Big%20Kahuna.webm.tar.gz&f=Crosstab%20Explained.ipynb&a=b&m=plok%202001.tar.gz
I tried many RegEx, and finally I found one that did not split the file names when it encounter the escaped character:
"(?:\w*:\/\/)?((?:[\w-_]*\.?)+:?\d*(?:\/?[\w-_.]+\/?)*)[\?]?[\&]?([\w-_]*)?=?([\/\w-_\?\)%\.\(\*\[\]\^<>\\]*)?[\&]?([\w-_]*)?=?([\/\w-_\?\)%\.\(\*\[\]\^<>\\]*)?[\&]?([\w-_]*)?=?([\/\w-_\?\)%\.\(\*\[\]\^<>\\]*)?[\&]?([\w-_]*)?=?([\/\w-_\?\)%\.\(\*\[\]\^<>\\]*)?"g
You can test it here: https://regex101.com/r/LRWlif/7
The results are a mess:
match,group,is_participating,start,end,content
1,0,yes,0,148,https://content.com/pbpython.py/notebooks/thirsty-allies.mov?file=The%20Big%20Kahuna.webm.tar.gz&f=Crosstab%20Explained.ipynb&a=b&m=plok%202001.tar.gz
1,1,yes,8,60,content.com/pbpython.py/notebooks/thirsty-allies.mov
1,2,yes,61,65,file
1,3,yes,66,94,The%20Big%20Kahuna.webm.tar.gz
1,4,yes,95,96,f
1,5,yes,97,123,Crosstab%20Explained.ipynb
1,6,yes,124,125,a
1,7,yes,126,127,b
1,8,yes,128,129,m
1,9,yes,130,148,plok%202001.tar.gz
2,0,yes,148,148,
2,1,yes,148,148,
2,2,yes,148,148,
2,3,yes,148,148,
2,4,yes,148,148,
2,5,yes,148,148,
2,6,yes,148,148,
2,7,yes,148,148,
2,8,yes,148,148,
2,9,yes,148,148,
The only good thing is that the filenames are all matched somehow, with no split parts, with the exception of "thirsty-allies.mov" that is matched along some url parts.
Also there is the issue that not all escape characters can be part of a filename. %2F for example is the "/" that separate folders in paths, and should not considered part of the match.
For example:
https://www.contoso.com/sites/marketing/documents/Shared%20Documents/Forms/AllItemA.aspx?RootFolder=%2Fsites%2Fmarketing%2Fdocuments%2FShared%20Documents%2FPFProduct%20Promotion%202001.docx&FolderCTID=0x012000F2A09653197F4F4F919923797C42ADEC&View=%7BCD527605-9A7A-448D-9A35-67A33EF9F766%7D
With the same RegEx we get this result:
match,group,is_participating,start,end,content
1,0,yes,0,288,https://www.contoso.com/sites/marketing/documents/Shared%20Documents/Forms/AllItemA.aspx?RootFolder=%2Fsites%2Fmarketing%2Fdocuments%2FShared%20Documents%2FPFProduct%20Promotion%202001.docx&FolderCTID=0x012000F2A09653197F4F4F919923797C42ADEC&View=%7BCD527605-9A7A-448D-9A35-67A33EF9F766%7D
1,1,yes,8,56,www.contoso.com/sites/marketing/documents/Shared
1,2,yes,56,56,
1,3,yes,56,99,%20Documents/Forms/AllItemA.aspx?RootFolder
1,4,yes,99,99,
1,5,yes,100,188,%2Fsites%2Fmarketing%2Fdocuments%2FShared%20Documents%2FPFProduct%20Promotion%202001.docx
1,6,yes,189,199,FolderCTID
1,7,yes,200,240,0x012000F2A09653197F4F4F919923797C42ADEC
1,8,yes,241,245,View
1,9,yes,246,288,%7BCD527605-9A7A-448D-9A35-67A33EF9F766%7D
2,0,yes,288,288,
2,1,yes,288,288,
2,2,yes,288,288,
2,3,yes,288,288,
2,4,yes,288,288,
2,5,yes,288,288,
2,6,yes,288,288,
2,7,yes,288,288,
2,8,yes,288,288,
2,9,yes,288,288,
As you can see, the filename to match is:
PFProduct%20Promotion%202001.docx
but the RegEx matched:
%2Fsites%2Fmarketing%2Fdocuments%2FShared%20Documents%2FPFProduct%20Promotion%202001.docx
How can I get just the filenames and nothing else?

There is no language tagged, but if you know that you always have urls you might use
(?<=[=\/]|%2F)(?:(?!%2F)[^?&\s\/])+\.\w+(?=[?&]|$)
Explanation
(?<= Positive lookbehind, assert what is to the left of the current position is
[=\/] Match either = or /
| Or
%2F Match literally
) Close the lookbehind
(?: Non capture group
(?!%2F)[^?&\s\/] Match 1 char other than what is listed in the character class if %2F is not directly to the right of the current position
)+ Close the non capture group and repeat 1+ times
\.\w+ Match a dot and 1 or more word characters
(?=[?&]|$) Positive lookahead, assert either ? or & or the end of the string directly to the right of the current position
Regex demo
Other variations
Or with a capture group if the lookbehind does not work with not fixed width:
(?:[=\/]|%2F)((?:(?!%2F)[^?&\s\/])+\.\w+)(?=[?&]|$)
Regex demo
In languages where an infinite quantifier in the lookbehind is supported:
(?<=https?:\/\/\S*(?:[=\/]|%2F))(?:(?!%2F)[^?&\s\/])+\.\w+(?=[?&]|$)
Regex demo

Match a part of a string using regex

I have a string and would like to match a part of it.
The string is Accept: multipart/mixedPrivacy: nonePAI: <sip:4168755400#1.1.1.238>From: <sip:4168755400#1.1.1.238>;tag=5430960946837208_c1b08.2.3.1602135087396.0_1237422_3895152To: <sip:4168755400#1.1.1.238>
I want to match PAI: <sip:4168755400#
the whitespace can be a word so i would like to use .* but if i used that it matches most of the string
The example on that link is showing what i'm matching if i use the whitespace instead of .*
(PAI: <sip:)((?:\([2-9]\d{2}\)\ ?|[2-9]\d{2}(?:\-?|\ ?))[2-9]\d{2}[- ]?\d{4})#
The example on that link is showing what i'm trying to achieve with .* but it should only match PAI: <sip:4168755400#
(PAI:.*<sip:)((?:\([2-9]\d{2}\)\ ?|[2-9]\d{2}(?:\-?|\ ?))[2-9]\d{2}[- ]?\d{4})#
I tried lookaround but failing.
Any idea?
thanks

Matching the single space can be updated by using a character class matching either a space or a word character and repeat that 1 or more times to match at least a single occurrence.
Note that you don't have to escape the spaces, and in both occasions you can use an optional character class matching either a space or hyphen [ -]?
If you want the match only, you can omit the 2 capturing groups if you want to.
(PAI:[ \w]+<sip:)((?:\([2-9]\d{2}\) ?|[2-9]\d{2}[ -]?)[2-9]\d{2}[- ]?\d{4})#
Regex demo

The regex should be like
PAI:.*?(<sip:.*?#)
Explanation:
PAI:.*? find the word PAI: and after the word it can be anything (.*) but ? is used to indicate that it should match as few as possible before it found the next expression.
(<sip:.*?#) capturing group that we want the result.
<sip:.*?# find <sip: and after the word it can be anything .*? before it found #.
Example

Regular expression not matching specific string

My use case is as follows: I would like to find all occurrences of something similar to this /name.action, but where the last part is not .action eg:
name.actoin - should match
name.action - should not match
nameaction - should not match
I have this:
/\w+.\w*
to match two words separated by a dot, but I don't know how to add 'and do not match .action'.

Firstly, you need to escape your . character as that's taken as any character in Regex.
Secondly, you need to add in a Match if suffix is not present group - signified by the (?!) syntax.
You may also want to put a circumflex ^ to signify the start of a new line and change your * (any repetitions) to a + (one or more repititions).
^/\w+\.(?!action)\w+ is the finished Regex.

^\w+\.(?!action)\w*

You need to escape the dot character.

\w+\.(?!action).*
Note the trailing .* Not sure what you want to do after the action text.
See also Regular expression to match string not containing a word?

You'll need to use a zero-width negative lookahead assertion. This will let you look ahead in the string, and match based on the negation of a word.
So the regex you'd need (including the escaped . character) would look something like:
/name\.(?!action)/