Regex - match everything after the second to last dash

[gwiz]

Hi all, I am trying to match everything after the second to last dash in a file which contains strings with hyphens or dashes. In each line is a string with a series of letters, numbers, and dashes. I would just like to extract everything after the second to last dash.

See examples below:

ab2372347234tfashdjfawhewe-c3

ab534572hasdfaj32rahafd32135466324-c1

dude-fhdhe12-ab5438472dsfawe35b3-c4

abtt78923dahdfajh23498kljcxcze

8ver238234923adfadhfahdabc33

gretorg-xsss47-hireball-rhetaama3-01

cn3-vov-4

YCMCDE7888132892-5

gretvrg-dae01-hetprotesh-dug-02

pret-grab01-vov-sebastian-03

Therefore for "gretvrg-dae01-hetprotesh-dug-02" I would just like dug-02 and then the next step would be to have "dug" in one column and "02" in another. For "cn3-vov-4" I would like "vov-4" and the next step would be to have "vov" in one column and "4" in another. For "dude-fhdhe12-ab5438472dsfawe35b3-c4" I would like "ab5438472dsfawe35b3-c4" and then the next step would be to have "ab5438472dsfawe35b3" in one column and "c4" in another. Etc etc.

Some have four dashes, some have three or two dashes, and some have none as you can see.

So that is why I would like to grab everything after the second to last dash. For the ones that don't have a dash its no big deal because I am planning to just bring those in at the end anyways. I am not having success working on this, as I have for the whole day so I would appreciate any help.

I tried doing this in a regex tool on tokenize output method, which gets everything after the last dash but thats the closest I can get: [^-]+$

Thank you so much for the help!

[MarqueeCrew · Accepted solution]

From my iPhone.

Does this help?

.*-(.*?-.*)

Cheers,

Mark

[gwiz]

@MarqueeCrew It does work, I believe! I am going to run it through a few more files but yes I appreciate your help. Can you clarify/explain what your solution is doing, though, so I may better understand the regex syntax? Thank you so much for the help!

[MarqueeCrew]

I'm looking for everything up to the last - and capturing everything that has a - in it. So the last dash is then truly the second to last dash.

Try regex101.com and enter the expression there. It will give you a very thorough explanation.


Glad to have helped.

Cheers,

Mark

[gwiz]

Okay that makes sense conceptually, like high-level. Looking at the syntax can you maybe explain it per each part of what you wrote? I am having trouble deciphering that from what you provided is all.

[MarqueeCrew]

.*-(.*?-.*)

.* looks for any character zero or more times

- looks for the last dash that occurs before the group of characters contained in the parentheses.

(.*?-.*) is the desired pattern

.*? Is the first set of any characters until the first occurrence of the next pattern.

- looks for a dash.

.* is everything else.

By defining the group as the stuff before and after the last dash, I achieved your objective. Hopefully this solves the challenge.

Will we meet at inspire in Nashville?

Cheers,

Mark

[gwiz]

@MarqueeCrew Thanks for the explanation(s). In response, what does the ? do in .*? before the dash? And what in this solution makes it look at the end (i.e. last two dashes) and not any prior sequence of that (i.e. what in the solution is telling it to look at the last two dashes and not the first two or middle two dashes)?

[MarqueeCrew]

It finds the first occurrence of the dash

.*- Finds the last dash
.*- Finds the first

[gwiz]

@MarqueeCrew Okay I think I'm starting to get it more. Is that a rule with the ? then (i.e. does always putting a ? before something mean you find the first occurrence of that thing/sequence?)

[MarqueeCrew]

Yes. A good read is:

https://www.oreilly.com/library/view/mastering-regular-expressions/0596528124/

You can also search YouTube. I have an intro here:

Alteryx RegEx Beginner Tutorial
https://youtu.be/pTZj2U2SDFA

Cheers,

Mark