Ruby single quote escaping madness

gistfile1.txt

Ok, so I'm trying to replace a ' character with \' in a ruby string. I have working code, but it was 
*way* too painful getting there for my taste.

Take a look:

ree-1.8.7-2010.02 :001 > single_quote = "\'"
 => "'" 
ree-1.8.7-2010.02 :003 > single_quote.gsub(/'/, "\\\'")
 => "" 
ree-1.8.7-2010.02 :004 > single_quote.gsub(/'/) {|c| "\\'"}
 => "\\'" 

I really expected my second attempt to work. I'm annoyed that I had to resort to using the block form 
of gsub.

I think I understand a little bit about what's going on, I'll try to work it out here.

In the second argument (ie: the replacement string) ruby allows you to use backreferences.

ree-1.8.7-2010.02 :017 > "asdf".gsub(/(a)/, "\\0\\0")
 => "aasdf" 
ree-1.8.7-2010.02 :018 > "asdf".gsub(/(a)/, '\\0\\0')
 => "aasdf" 
ree-1.8.7-2010.02 :019 > 

Actually, I was really surprised that works with both types of quotes... I didn't expect that.

Anyway, this means that in order to have a literal backslash in the replacement string, it must be 
escaped (or else ruby will thing it's an indicator of a backreference).  Since backslashes are escaped 
anyway, I have to double escape them:

ree-1.8.7-2010.02 :025 > "asdf".gsub(/(a)/, "\\")
 => "\\sdf" 
ree-1.8.7-2010.02 :026 > 

(Don't be confused, that's actually ONE backslash in the output, irb just prints it twice)

I guess that means four blackslashes ought to do it:

ree-1.8.7-2010.02 :037 > "'".gsub(/'/, "\\\\'")
 => "\\'" 
ree-1.8.7-2010.02 :038 > 

Looks good; but the block form is more readable.

Interestingly, if I wanted to replace a backslash with an escaped backslash (ie: two backslashes), I would
have needed *eight* backslashes in the replacement string. That's just ridiculous.

Sometimes, ruby is a very hard language to love.

Thanks man! You saved my day! (and night)

Oh wow! That's wild. This gist is 12 years old! I'm glad it helped!

another one saved in year 13, thank you! :-)