Ruby string sub without regex back references

Question

I'm trying to do a simple string sub in Ruby.

The second argument to sub() is a long piece of minified JavaScript which has regular expressions contained in it. Back references in the regex in this string seem to be effecting the result of sub, because the replaced string (i.e., the first argument) is appearing in the output string.

Example:

input = "string <!--tooreplace--> is here"
output = input.sub("<!--tooreplace-->", "\&")

I want the output to be:

"string \& is here"

Not:

"string & is here"

or if escaping the regex

"string <!--tooreplace--> is here"

Basically, I want some way of doing a string sub that has no regex consequences at all - just a simple string replace.

Answer 1

To avoid having to figure out how to escape the replacement string, use Regex.escape. It's handy when replacements are complicated, or dealing with it is an unnecessary pain. A little helper on String is nice too.

input.sub("<!--toreplace-->", Regexp.escape('\&'))

Answer 2

You can also use block notation to make it simpler (as opposed to Regexp.escape):

=> puts input.sub("<!--tooreplace-->") {'\&'}
string \& is here