From: Tim Hunter <rmagick@...>
Date: 2009-02-11T03:22:27+09:00
Subject: Re: regex to escape special characters

Jon Garvin wrote:
> I've got the following string...
> 
> "This is ( a test"
> 
> And I want to do a regex gsub on it to turn it into...
> 
> "This is \( a test"
> 
> In irb, If I start with...
> 
>  "This is ( a test".gsub(/[\(]/,'\&')        => "This is ( a test"
> 
> And then progressively added more backslashes, I get the following
> results, none of which are what I'm looking for.  The second one is,
> IMO, the one that should work.
> 
> "This is ( a test".gsub(/[\(]/,'\\&')   => "This is ( a test"
> "This is ( a test".gsub(/[\(]/,'\\\&')  => "This is \\& a test"
> "This is ( a test".gsub(/[\(]/,'\\\\&') => "This is \\& a test"
> "This is ( a test".gsub(/[\(]/,'\\\\\&')=> "This is \\( a test"
> 
> 
> Am I just having a serious case of the mondays, or is there a bug in how
> Ruby deals with \ characters when trying to represent an actual single \
> character?
> 
> I'm using ruby 1.8.6 (2007-09-24 patchlevel 111) [i486-linux]

irb shows you the result using p, which escapes special characters in 
the string it displays. Use puts to see the actual string.

C:\>irb
irb(main):001:0> x = "This is ( a test"
=> "This is ( a test"
irb(main):002:0> x.gsub(/\(/, '\\\(')
=> "This is \\( a test"
irb(main):003:0> y = x.gsub(/\(/, '\\\(')
=> "This is \\( a test"
irb(main):004:0> puts y
This is \( a test
=> nil
irb(main):005:0>
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