Using Ruby + regex, given:
I want to obtain just: 31313131313
ie, what is between starting-middle+ and mysite.com
Here's what I have so far:
to = '[email protected]'
to.split(/\+/@mysite.com.*/).first.strip
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1This question is incredibly similar to your other question asked two hours later.the Tin Man– the Tin Man2010-11-19 00:16:59 +00:00Commented Nov 19, 2010 at 0:16
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4 Answers
Between 1st + and 1st @:
to[/\+(.*?)@/,1]
Between 1st + and last @:
to[/\+(.*)@/,1]
Between last + and last @:
to[/.*\+(.*)@/,1]
Between last + and 1st @:
to[/.*\+(.*?)@/,1]
2 Comments
stack1
to[/\+(.*?)@/,1] - The number 1 is for first match found in string ?
Nakilon
@stack1, yes it is for what is inside the first
(). Just like .match(//)[1] or .match(//).group(1) in some other languages. Usually you are retrieving the single substring when applying regex, so the ,1 is rather usual in Ruby.Here is a solution without regex (much easier for me to read):
i = to.index("+")
j = to.index("@")
to[i+1..j-1]
Here is a solution based on regex lookbehind and lookahead.
email = "[email protected]"
regex = /(?<=\+).*(?=@)/
regex.match(email)
=> #<MatchData "31313131313">
Explanation
Lookahead is indispensable if you want to match something followed by something else. In your case, it's a position followed by @, which express as
(?=@)Lookbehind has the same effect, but works backwards. It tells the regex engine to temporarily step backwards in the string, to check if the text inside the lookbehind can be matched there. In your case, it's a position after
+, which express as(?<=\+)
so we can combine those two conditions together.
lookbehind (what you want) lookahead
↓ ↓ ↓
(?<=\+) .* (?=@)
Reference
1 Comment
abax
This is a really well-constructed answer. Thank you
If you care about readability, i suggest to just use "split", like so: string.split("from").last.split("to").first or, in your case:
to.split("+").last.split("@").first
use the limit 2 if there are more occurancies of '+' or '@' to only care about the first occurancy: to.split("+",2).last.split("@",2).first
