From: Austin Ziegler <halostatue@...>
Date: 2004-08-18T04:58:36+09:00
Subject: Re: Bug in gsub with "\\" ?

On Wed, 18 Aug 2004 04:47:16 +0900, Garance A Drosehn <drosihn@gmail.com> wrote:
> In a program I worked on, I wanted to replace all single-quotes
> with a backslash+single_quote.  The following simple program:
> 
>   somestr = "'This isn't right.'"
>   printf " Orig A:  %s\n", somestr
>   printf " Test A1: %s\n", somestr.gsub(/'/, "\\'")
>   printf " Test A2: %s\n", somestr.gsub(/'/, "\\=")
>   printf " Test A3: %s\n", somestr.gsub(/'/) { |s| "\\'"}
>   printf "\n"
>   somestr = "=This isn=t right.="
>   printf " Orig B:  %s\n", somestr
>   printf " Test B1: %s\n", somestr.gsub(/=/, "\\'")
>   printf " Test B2: %s\n", somestr.gsub(/=/, "\\=")
>   printf " Test B3: %s\n", somestr.gsub(/=/) { |s| "\\="}
>   exit 0
> 
> Prints out:
> 
>  Orig A:  'This isn't right.'
>  Test A1: This isn't right.'This isnt right.'t right.
>  Test A2: \=This isn\=t right.\=
>  Test A3: \'This isn\'t right.\'
> 
>  Orig B:  =This isn=t right.=
>  Test B1: This isn=t right.=This isnt right.=t right.
>  Test B2: \=This isn\=t right.\=
>  Test B3: \=This isn\=t right.\=
> 
> The output from TestA1 and TestB1 seem a bit odd to me...
> I am running:  ruby 1.8.2 (2004-07-29) [i386-freebsd5]

This is working as designed. Not clean, but it's right.

  irb(main):003:0> puts somestr.gsub(/'/, "\\\\'") # => \'This isn\'t right.\'

You need \\ for each \ you want in the actual string; your version
goes from \\' to \', which is just '. Your second version (\\=)
represents a string that isn't a "valid" escape.

-austin
-- 
Austin Ziegler * halostatue@gmail.com
               * Alternate: austin@halostatue.ca