regex for symbol or nothing

Question

I have a string where I need to parse the values such that it some times exist between[''] and sometimes not.

Eg:

Input
    1. blah .... REASON: ['elm H1MM_rr'], blah ....
    2. blah .... REASON: elm H1MM_rr, blah .... 
    3. blah .... REASON: elm H1MM_rr. 
    4. blah .... REASON: ['elm H1MM_rr'].

The elm H1MM_rr is just an example here. It could be any string after REASON:

I tried REASON: ([^,. ]+)")but this still not working for ['']

Output I am looking for = elm H1MM_rr

Can some one suggest me a regex(java pattern) which can work for both strings ?

Give your desired output in the question. It would be helpful. Which language you are using? — Sumit S Chawla, Jun 21 '18 at 05:50
yes, please restructure your question so the input and output is much clearer~ — oldboy, Jun 21 '18 at 06:14
Try [`REASON:\s*(?|\['([^']*)']|([^,.\s]+))`](https://regex101.com/r/TTElaB/1) — Wiktor Stribiżew, Jun 21 '18 at 06:45

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

1

(\[')?elm('])? should do the trick. This will match elm, ['elm, elm'], and ['elm'].

You also may want to use (?:\[')?elm(?:'])?. (Check the documentation that I've linked below.)

? will match something 0 or 1 times

You have to escape the first [, otherwise it treats everything between the [ and ] as a character set.

According to Your Edits

Now that you have clarified certain things and modified your question, the following code should work (at least in JavaScript):
REASON: (\[')?[\w/]{0,}(\s)?[\w/]{0,}('\])?
REASON: (?:\[')?[\w/]{0,}(\s)?[\w/]{0,}(?:'\])?

From the following input:

blah .... REASON: ['elm H1MM_rr'], blah ....
blah .... REASON: /lm H1MM_rr, blah ....
blah .... REASON: elm H1MM_rr.
blah .... REASON: ['elm H1MM_rr'].
blah .... REASON: [' '].

It will match:

REASON: ['elm H1MM_rr']
REASON: /lm H1MM_rr
REASON: elm H1MM_rr
REASON: ['elm H1MM_rr']
REASON: [' ']

You may find this documentation useful. You may also find this SO thread useful, if you'd like to modify the query to possibly make it more concise.

edited Jun 20 '20 at 09:12

Community

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answered Jun 21 '18 at 06:09

oldboy

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The elm H1MM_rr is just an example here. It could be any string after REASON: – user3407267 Jun 22 '18 at 16:21
@user3407267 ok, well, which characters would be allowed and which characters would not be allowed? – oldboy Jun 22 '18 at 16:56
It will be always preceded with REASON: – user3407267 Jun 22 '18 at 17:14
sometimes it will be with [' '] and sometime not but will always end with either . or , – user3407267 Jun 22 '18 at 17:15
@user3407267 yes, i know but which characters can be after reason and between the brackets and single quotes??? – oldboy Jun 22 '18 at 17:15
It would be a-z A-Z _ / – user3407267 Jun 22 '18 at 17:19
@user3407267 umm... in your question above, you also include `1`, and `.`??? ALSO, where is the cutoff? in other words, should a match also include `, blah ....` and or `.` and or `. ` at the end of each string? – oldboy Jun 22 '18 at 17:29
sorry it include 0-9 as well.. the cut off is either , or . – user3407267 Jun 22 '18 at 17:33
@user3407267 i've edited my answer accordingly. does it work in Java?? – oldboy Jun 22 '18 at 17:44
@user3407267 well? – oldboy Jun 22 '18 at 17:49
not exactly .. I am getting [ "REASON: ['elm H1MM_rr']", null ] – user3407267 Jun 22 '18 at 17:52
I tried - "REASON: (?:\\[')?[\\w/]{0,}(\\s)?[\\w/]{0,}(?:'\\])?" – user3407267 Jun 22 '18 at 17:52
@user3407267 um... ["**`REASON: ['elm H1MM_rr']`**", null] is the correct output is it not???? – oldboy Jun 22 '18 at 17:53
But with this :"REAOSN: (\\[')?s*([^,.]+)?s*([^,.]+)('\\])?" I am getting = [ "REAOSN: ['elm H1MM_rr']", "['", "elm H1MM_rr''", "]", null.string ] – user3407267 Jun 22 '18 at 17:54
Yeah..generally it will give me the expected string 2nd or 3rd element as the array.. I am trying to get tat string alone – user3407267 Jun 22 '18 at 17:55
@user3407267 you're not even using the query that i created for you. i'm sorry, but i've wasted enough time at this point trying to guess exactly what it is you're looking for. ["**`REASON: ['elm H1MM_rr']`**", null] seemed like legit output that matched what you said you were looking for... in that particular output the string is the first element in the array... likely `ele[0]` – oldboy Jun 22 '18 at 17:57
@user3407267 so `["REASON: ['elm H1MM_rr']", null]` is what you were looking for (right?), whereby in that particular output the string is the first element in the array, likely accessed by using something like `array[0]` – oldboy Jun 22 '18 at 17:59
Tats true but I am trying to get just elm H1MM_rr – user3407267 Jun 22 '18 at 19:04
@user3407267 what do u mean? also, what did you mean by **I tried REASON: ([^,. ]+)")but this still not working for ['']** in your original question? please edit your question and try to make it as clear as possible – oldboy Jun 22 '18 at 19:34

regex for symbol or nothing

1 Answers1

According to Your Edits