Backslashes in gsub (escaping and backreferencing)

Posted by polygenelubricants on Stack Overflow See other posts from Stack Overflow or by polygenelubricants
Published on 2010-06-12T11:48:07Z Indexed on 2010/06/12 11:52 UTC
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ruby

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regex

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replace

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escape-sequence

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backreference

Consider the following snippet:

puts 'hello'.gsub(/.+/, '\0 \\0 \\\0 \\\\0')

This prints (as seen on ideone.com):

hello hello \0 \0

This was very surprising, because I'd expect to see something like this instead:

hello \0 \hello \\0

My argument is that \ is an escape character, so you write \\ to get a literal backslash, thus \\0 is a literal backslash \ followed by 0, etc. Obviously this is not how gsub is interpreting it, so can someone explain what's going on?

And what do I have to do to get the replacement I want above?

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