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http://something.com/bOhxBeD,SyhyTGi,TMDDSIB,U72gx2J,kQTIRy9,7VXgGDw,eSxIcK6,S5oNlnn,WBHHsLk,BdMGd2d,U9kNlsF,cHVyc7Y,D83kaJ5,cLWgdSO,iWtCIF3,ount8L6

I have tried to get the value: bOhxBeD, SyhyTGi and so on. This is what I come up with ( yes fairly simple ) /([a-zA-Z0-9]{7})/, it seems to work with PCRE: 

([a-zA-Z0-9]{7})

Regular expression visualization

Debuggex Demo

But when it comes to Ruby, I use it like this : 

str.match(/([a-zA-Z0-9]{7})/)
#<MatchData "bOhxBeD" 1:"bOhxBeD">

it doesn't seem to work. Can anyone point out what's wrong with this regex ? Thanks

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  • 1
    Not an answer to your actual question, but this may be better suited to methods other than regexes. eg: require 'uri'; URI(str).path[1..-1].split(',') Commented Aug 27, 2014 at 6:43
  • 1
    @TimPeters this is a good answer too, thanks. But somehow to me when I look at this kind of thing, I think about regex anyway. So I try hard to learn it properly. But still, nice solution there :) Commented Aug 27, 2014 at 6:45

5 Answers 5

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3

You need to add word boundary \b inorder to match an exact 7 alphanumeric characters. 

\b[a-zA-Z0-9]{7}\b

DEMO

irb(main):006:0> "http://something.com/bOhxBeD,SyhyTGi,TMDDSIB,U72gx2J,kQTIRy9,7VXgGDw,eSxIcK6,S5oNlnn,WBHHsLk,BdMGd2d,U9kNlsF,cHVyc7Y,D83kaJ5,cLWgdSO,iWtCIF3,ount8L6".scan(/\b([a-zA-Z0-9]{7})\b/)
=> [["bOhxBeD"], ["SyhyTGi"], ["TMDDSIB"], ["U72gx2J"], ["kQTIRy9"], ["7VXgGDw"], ["eSxIcK6"], ["S5oNlnn"], ["WBHHsLk"], ["BdMGd2d"], ["U9kNlsF"], ["cHVyc7Y"], ["D83kaJ5"], ["cLWgdSO"], ["iWtCIF3"], ["ount8L6"]]
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2 
 (?!.*?\/)[a-zA-Z0-9]{7}

Is should be this.Or else it will pick 7 letter words from link as well."somethi" will be in ans.But i guess that is not required.

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it uses a negative lookahead i.e ?!.So anything which matches negative lookahead cannot be matched by the main matcher.So negative lookahead says match anything upto last /.So the ans can now come from raminign string only.That is what was required.
2

match only picks up the first match.
You can try the global version of match which is scan.
You can use scan to search string not containing specific characters using [^...]: 

str.scan(/[^\/\.\,]+/)[3..-1]   
#=> ["bOhxBeD", "SyhyTGi", "TMDDSIB", "U72gx2J", "kQTIRy9", "7VXgGDw", "eSxIcK6", "S5oNlnn", "WBHHsLk", "BdMGd2d", "U9kNlsF", "cHVyc7Y", "D83kaJ5", "cLWgdSO", "iWtCIF3", "ount8L6"]

Update:
If you know that the strings between the comma are always 7 characters, you can use this instead: 

   str.scan(/[^\/\.\,]{7}/)[1..-1]
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1

it happens because your regexp match just one element which contain 7 chars, nothing more, as simple solution could be: 

str.match(/\/(.*)\z/)[1].split(',')
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You could use String#[] and String#split:

str[/.*\/(.*)/,1].split(',')
  #=> ["bOhxBeD", "SyhyTGi", "TMDDSIB", "U72gx2J", "kQTIRy9", "7VXgGDw",
  #    "eSxIcK6", "S5oNlnn", "WBHHsLk", "BdMGd2d", "U9kNlsF", "cHVyc7Y",
  #    "D83kaJ5", "cLWgdSO", "iWtCIF3", "ount8L6"]

.*\/ in the regex, "greedy" as it is, will consume characters up to and including the last forward slash in the string. Capture group #1 (.*) sucks up the remainder of the string and, due to the presence of ,1, returns it. split(',') then breaks up the string to give you the desired array.

Another way:

str[str[/.*\//].size..-1].split(',')
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