Regex in Ruby not working

Question

I have a string from which I want to extract a certain part:

Original String: /abc/d7_t/g-12/jkl/m-n3/pqr/stu/vwx

Result Desired: /abc/d7_t/g-12/jkl/

The number of characters can vary in the entire string. It has alphabets, numbers, underscore and hyphen. I want to basically cut the string after the 5th "/"

I tried a few regex, but it seems there is some mistake with the format.

So what's the rule you want to apply? Always cut before pqr? Or after the 6th instance of /? Or the 16th character? Or the 4th digit? What? Clarify this and you'll be halfway there... — Jean-François Corbett
– Jean-François Corbett, Commented Dec 11, 2012 at 8:28
I did something like this : (/[wW]/[wW]/[wW]/[wW]/[wW]/)....I m not sure how to find a "/" and also w & W doesn't include the symbol '-' which is present in my string at many places — Pi Horse
– Pi Horse, Commented Dec 11, 2012 at 8:30
@Jean-FrançoisCorbett : The number of characters can vary. I want to cut the string after the 5th "/" — Pi Horse
– Pi Horse, Commented Dec 11, 2012 at 8:31
Why not just split it with / and join the first 5 parts with / ? — halfelf
– halfelf, Commented Dec 11, 2012 at 8:39

Faiz · Accepted Answer · 2012-12-11 08:46:42Z

3

If a non-regexp approach is acceptable, how about this:

s.split('/').take(n).join('/')+'/'

Where s if your string (in your case: /abc/d7_t/g-12/jkl/m-n3/pqr/stu/vwx).

def cut_after(s, n)
  s.split('/').take(n).join('/')+'/'
end

Then

cut_after("/abc/d7_t/g-12/jkl/m-n3/pqr/stu/vwx", 5)

should work. Not as compact as a regexp, but some people may find it clearer.

answered Dec 11, 2012 at 8:46

Faiz

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1 Comment

Faiz Over a year ago

That's fine if you hate regexes - making it clear that a non-regex solutions are also acceptable would be useful(people, including myself, love to find a regexp fix to solutions with the goal of doing it in regexps ;-))

marcus erronius · Accepted Answer · 2012-12-11 09:21:37Z

2

The regexp would be: %r(/(?:[^/]+/){4}). Note that it is a good idea in this case to use the %r literal version to avoid escaping slashes. Unescaped slashes are likely the cause of your format errors.

edited Dec 11, 2012 at 9:21

answered Dec 11, 2012 at 8:47

marcus erronius

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3 Comments

Johny Skovdal Over a year ago

Please note my comment as well. It's the 6th slash he wants (he forgot to include the first in the count).

marcus erronius Over a year ago

Looks like 5 slashes to me. I just double counted. Also, before I posted I checked my result in irb against his desired result.

Johny Skovdal Over a year ago

wow, my bad, I must have had an error in my original Regex I tested. -.-

Himanshu · Accepted Answer · 2012-12-11 08:37:25Z

1

Match any sequence of chars except '/' 4 times :-

(\/[^\/]+){4}\/

answered Dec 11, 2012 at 8:37

Himanshu

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