Question

The task is simple – I have a string like "I don't know" and I want substitute ' with \' (I know that I don’t have to escape single quotes). How can I do it?

Answer 1

Try using the block form, it should work in all versions of Ruby:

s.gsub(/'/) {"\\'"}
# => "I don\\'t know"

[Edit]

The reason is that the gsub method has special handling for backslash sequences in the replacement string which correspond to the special match variables. So you can use $' (and $1, etc.) directly in the substituted string by using the form \\' (and \\1, etc.) instead.

The block form of gsub doesn’t have this behavior, so that’s the workaround when you’re trying to sub in a string that looks like a special backslash sequence.