# Question about text parsing **URL:** \ **Category:** Ruby\ **Created:** [July 22, 2009, 11:57pm UTC](https://www.ruby-forum.com/t/question-about-text-parsing/172533 "2009-07-22T23:57:35Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![stepheneb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/71e660/32.png) [@stepheneb](https://www.ruby-forum.com/u/stepheneb)\ **Post date:** [July 22, 2009, 11:57pm UTC](https://www.ruby-forum.com/t/question-about-text-parsing/172533/1 "2009-07-22T23:57:35Z")
Hello, I am new to ruby and had a question about parsing text. I am trying to parse out the first IP address from a string. I have a working solution, but it seems like a rather round about way to do it. This is my current method: str = " inet addr:192.168.1.118 Bcast:192.168.1.255 Mask:255.255.255.0" ipAddr = ((str.split(’:’))[1].split)[0] Is there a better way to do this? Thanks in advance. ---
**Author:** ![stepheneb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/71e660/32.png) [@stepheneb](https://www.ruby-forum.com/u/stepheneb)\ **Post date:** [July 23, 2009, 12:19am UTC](https://www.ruby-forum.com/t/question-about-text-parsing/172533/2 "2009-07-23T00:19:49Z")
On Wednesday 22 July 2009 14:58:47 Stephen Beard wrote: > ipAddr = ((str.split(’:’))[1].split)[0] > > Is there a better way to do this? Thanks in advance. regexp: str.scan(/addr:([^\s]+)/)[0][0] string math: str.slice(str.index(’:’)+1, str.index(’ B’)-str.index(’:’)-2) ---
**Author:** ![stepheneb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/71e660/32.png) [@stepheneb](https://www.ruby-forum.com/u/stepheneb)\ **Post date:** [July 23, 2009, 1:12am UTC](https://www.ruby-forum.com/t/question-about-text-parsing/172533/3 "2009-07-23T01:12:03Z")
Thanks for the quick and thorough replies. They all look great. I am so terrible with regular expressions. Those links look like a good place to go to improve, thanks Rob. ---
**Author:** ![stepheneb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/71e660/32.png) [@stepheneb](https://www.ruby-forum.com/u/stepheneb)\ **Post date:** [July 23, 2009, 12:45am UTC](https://www.ruby-forum.com/t/question-about-text-parsing/172533/4 "2009-07-23T00:45:31Z")
On Jul 22, 2009, at 6:18 PM, spox wrote: > > str = " inet addr:192.168.1.118 Bcast:192.168.1.255 irb\> str = " inet addr:192.168.1.118 Bcast:192.168.1.255 Mask:255.255.255.0" =\> " inet addr:192.168.1.118 Bcast:192.168.1.255 Mask: 255.255.255.0" irb\> re = /\b\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}\b/ =\> /\b\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}\b/ irb\> str.scan(re) =\> [“192.168.1.118”, “192.168.1.255”, “255.255.255.0”] So the first one is just: str.scan(re).first or str.scan(re)[0] If you want to be tighter about matching valid IP addresses, look at the alternate regexps about halfway down this page: [http://www.regular-expressions.info/examples.html](http://www.regular-expressions.info/examples.html) or the grand-daddy one with explanation of all the details: [http://www.regular-expressions.info/regexbuddy/ipaccuratecapture.html](http://www.regular-expressions.info/regexbuddy/ipaccuratecapture.html) If you include the capturing groups, the String#scan keeps them: ## irb\> re1 = /\b(?:\d{1,3}.){3}\d{1,3}\b/ =\> /\b(?:\d{1,3}.){3}\d{1,3}\b/ irb\> re2 = /\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) .(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) .(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) .(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b/x =\> /\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) .(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) .(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) .(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b/x irb\> re3 = /\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?).){3} (?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b/x =\> /\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?).){3} (?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b/x irb\> [re, re1, re2, re3].each do |r| ?\> puts ‘-’\*30 irb\> puts r irb\> p str.scan(r) irb\> end; nil ## (?-mix:\b\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}\b) [“192.168.1.118”, “192.168.1.255”, “255.255.255.0”] ## (?-mix:\b(?:\d{1,3}.){3}\d{1,3}\b) [“192.168.1.118”, “192.168.1.255”, “255.255.255.0”] ## (?x-mi:\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) .(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) .(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) .(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b) [[“192”, “168”, “1”, “118”], [“192”, “168”, “1”, “255”], [“255”, “255”, “255”, “0”]] (?x-mi:\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?).){3} (?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b) [“192.168.1.118”, “192.168.1.255”, “255.255.255.0”] =\> nil -Rob Rob B. [http://agileconsultingllc.com](http://agileconsultingllc.com) removed\_email\_address@domain.invalid ---
**Author:** ![stepheneb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/71e660/32.png) [@stepheneb](https://www.ruby-forum.com/u/stepheneb)\ **Post date:** [July 23, 2009, 3:15am UTC](https://www.ruby-forum.com/t/question-about-text-parsing/172533/5 "2009-07-23T03:15:43Z")
Hi – On Thu, 23 Jul 2009, 7stud – wrote: > Stephen Beard wrote: > > > Thanks for the quick and thorough replies. They all look great. > > > > I am so terrible with regular expressions. Those links look like a good > > place to go to improve, thanks Rob. > > Always look to a string method first. split() rules the world, and > you’ve made good use of it. String method isn’t the opposite of regular expression, though. It’s important to understand regexes to use split (as well as scan and (g)sub) effectively. David ---
**Author:** ![stepheneb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/71e660/32.png) [@stepheneb](https://www.ruby-forum.com/u/stepheneb)\ **Post date:** [July 23, 2009, 2:56am UTC](https://www.ruby-forum.com/t/question-about-text-parsing/172533/6 "2009-07-23T02:56:18Z")
Stephen Beard wrote: > Thanks for the quick and thorough replies. They all look great. > > I am so terrible with regular expressions. Those links look like a good > place to go to improve, thanks Rob. Always look to a string method first. split() rules the world, and you’ve made good use of it. ---
**Author:** ![stepheneb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/71e660/32.png) [@stepheneb](https://www.ruby-forum.com/u/stepheneb)\ **Post date:** [July 23, 2009, 3:44am UTC](https://www.ruby-forum.com/t/question-about-text-parsing/172533/7 "2009-07-23T03:44:22Z")
Hi – On Thu, 23 Jul 2009, spox wrote: > > Mask:255.255.255.0" > > ipAddr = ((str.split(’:’))[1].split)[0] > > > > Is there a better way to do this? Thanks in advance. > > regexp: > str.scan(/addr:([^\s]+)/)[0][0] > > string math: > str.slice(str.index(’:’)+1, str.index(’ B’)-str.index(’:’)-2) Here’s a technique involving subscripting a string with a regular expressions. The number 1 at the end causes the whole thing to return the contents of the first parenthetical capture (which is all consecutive non-space characters following the first colon). str[/:(\S+)/,1] David ---
**Author:** ![stepheneb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/71e660/32.png) [@stepheneb](https://www.ruby-forum.com/u/stepheneb)\ **Post date:** [July 23, 2009, 3:51am UTC](https://www.ruby-forum.com/t/question-about-text-parsing/172533/8 "2009-07-23T03:51:22Z")
Perfect. Thanks. Wesley C…