Gsub and slash-ampersand in the substitution string

Ruby
1

Greetings,

I’m trying to do something that should be very simple: stick a “” in
front of
every instance of “&” in a string. However, the obvious code…

“this&that”.gsub!("&", “")
–> "thisthat” # OK!

“this&that”.gsub!("&", “\&”)
–> “this&that” # Wrong

…doesn’t work, because “&” means “last match” in gsub substitution
strings.
How can I escape this? I experimentally determined that entering
“\\\&”
(that’s six backslashes) gets the desired result, but I don’t really
understand why. Is there a less obscure way of doing this?

Cheers,
-jani

2

On Mon, Oct 09, 2006 at 08:58:09PM +0900, Jani Patokallio wrote:

–> “this&that” # Wrong

…doesn’t work, because “&” means “last match” in gsub substitution
strings.
How can I escape this? I experimentally determined that entering
“\\\&”
(that’s six backslashes) gets the desired result, but I don’t really
understand why. Is there a less obscure way of doing this?

I'm not sure, but I think that the problem is that you are using

double
quotes. So, the value you are passing is really the same as:

'\\\&'

Which, once you interpret the escape sequences, you have a literal ‘’
and a
literal ‘&’…

3

this was discussed several times, try searching for gsub and \ or
escaping or something similar. & is the last match, and \ is the
whole match. so you need to escape both. The correct solutions to this
‘quiz’ are posted somewhere, just google it :wink: