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Global Regular Expression matching in Ruby (using scan)

Regular expression 'engines' start at the left of an input string they're matching against, and counts are usually greedy, so by default they return "leftmost, longest" matches - which works for what users want in most cases.

However, sometimes you may want to work through all (non-overlapping) matches in a string - for example to pick up a series of email addresses or URLs from a line or block of text. In Ruby, you can achieve that through the scan method on a string. A single match:
  if myStringRecord =~ /\s*(\S{1,})@(\S+)\s*/
or changing that to a multiple or global match:
  myStringRecord.scan(/\s*(\S{1,})@(\S+)\s*/) do |tom,dick|
which is a loop populating the variables dick and tom.

Complete example [here]. Topic covered on our Ruby Courses.

Should you wish to match the shortest rather than longest alternatives, an additional ? character after the count(s) you want to vary should be added.
  "banana" =~ /a(.*)a/
  puts $1
  "banana" =~ /a(.*?)a/
  puts $1

outputs
  nan
  n


(written 2015-01-08)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
R109 - Ruby - Strings and Regular Expressions
  [4549] Clarrissa-Marybelle - too long to really fit? - (2015-10-23)
  [4505] Regular Expressions for the petrified - in Ruby - (2015-06-03)
  [3758] Ruby - standard operators are overloaded. Perl - they are not - (2012-06-09)
  [3757] Ruby - a teaching example showing many of the language features in short but useful program - (2012-06-09)
  [3621] Matching regular expressions, and substitutions, in Ruby - (2012-02-23)
  [3424] Divide 10000 by 17. Do you get 588.235294117647, 588.24 or 588? - Ruby and PHP - (2011-09-08)
  [2980] Ruby - examples of regular expressions, inheritance and polymorphism - (2010-10-02)
  [2623] Object Oriented Ruby - new examples - (2010-02-03)
  [2621] Ruby collections and strings - some new examples - (2010-02-03)
  [2614] Neatly formatting results into a table - (2010-02-01)
  [2608] Search and replace in Ruby - Ruby Regular Expressions - (2010-01-31)
  [2295] The dog is not in trouble - (2009-07-17)
  [2293] Regular Expressions in Ruby - (2009-07-16)
  [1891] Ruby to access web services - (2008-11-16)
  [1887] Ruby Programming Course - Saturday and Sunday - (2008-11-16)
  [1875] What are exceptions - Python based answer - (2008-11-08)
  [1588] String interpretation in Ruby - (2008-03-21)
  [1305] Regular expressions made easy - building from components - (2007-08-16)
  [1195] Regular Express Primer - (2007-05-20)
  [987] Ruby v Perl - interpollating variables - (2006-12-15)
  [986] puts - opposite of chomp in Ruby - (2006-12-15)
  [970] String duplication - x in Perl, * in Python and Ruby - (2006-12-07)


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