# Rewrite last using variable **URL:** \ **Category:** NGINX\ **Created:** [October 28, 2013, 1:56am UTC](https://www.ruby-forum.com/t/rewrite-last-using-variable/237165 "2013-10-28T01:56:47Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\ **Post date:** [October 28, 2013, 1:56am UTC](https://www.ruby-forum.com/t/rewrite-last-using-variable/237165/1 "2013-10-28T01:56:47Z")
Hi, consider the following simplified nginx config snippet: set $var “/url?par=val”; location = /a { rewrite ^ $var redirect; } location = /b { rewrite ^ $var last; } location = /url { proxy\_pass http://some\_backend; } For location a the redirect goes via the client and everything works just fine. For location b the redirect is internal and now the backend cannot process the request anymore. I found out that it in the 2nd case the backend sees a URL encoded form of the contents of $var. So the question mark has become %3F and naturally the backend can’t find the request parameters. I guess that the URL encoding also takes place in the first case, but here the client decodes the URL and thus everything is ok again. So here is my question: Is it possible in nginx to make rewrites with variables where the variable contains a URL with parameters like in the example? If yes, what do I need to change? If no, what other options do I have? Cheers, Ingo =;-\> ---
**Author:** ![Ingo\_Schmidt](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/a88e57/32.png) [@Ingo\_Schmidt](https://www.ruby-forum.com/u/Ingo_Schmidt)\ **Post date:** [October 28, 2013, 9:10am UTC](https://www.ruby-forum.com/t/rewrite-last-using-variable/237165/2 "2013-10-28T09:10:15Z")
On Mon, Oct 28, 2013 at 01:56:16AM +0100, Ingo Schmidt wrote: Hi there, > set $var “/url?par=val”; > location = /b { > rewrite ^ $var last; > } > For location b the redirect is internal and now the backend cannot > process the request anymore. > I guess that the URL encoding also takes place in the first case, but > here the client decodes the URL and thus everything is ok again. No; here what is sent to the client includes the bare ?. > Is it possible in nginx to make rewrites with variables where the > variable contains a URL with parameters like in the example? If yes, > what do I need to change? If no, what other options do I have? I believe it is intended to be “no”, for internal rewrites at least. You can do something like ``` set $var "/url"; set $vararg "par=val"; rewrite ^ $var?$vararg last; ``` Although you may need to be more subtle if you know that your backend handles “/url” and “/url?” differently, in case $vararg is empty. ## f Francis D. removed\_email\_address@domain.invalid ---
**Author:** ![Ingo\_Schmidt](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/a88e57/32.png) [@Ingo\_Schmidt](https://www.ruby-forum.com/u/Ingo_Schmidt)\ **Post date:** [October 28, 2013, 9:37am UTC](https://www.ruby-forum.com/t/rewrite-last-using-variable/237165/3 "2013-10-28T09:37:07Z")
Hi! > I believe it is intended to be “no”, for internal rewrites at least. > Hmm, any reason why it might be intended? > Also, it would be nice if the docs could mention this, because I find it > unintuitive, if rewrite behaves differently depending on the rewrite > type. > You can do something like set $var “/url”; set $vararg “par=val”; > rewrite ^ $var?$vararg last; > Well, in my case that is exactly what I am trying to avoid, because my > variable is set in a map and I would have to create two maps then, one > with the URLs, the other with arguments. > And, as you already pointed out, sometimes the argument is optional. Hmm, but it looks like this is my only option right now. Anyway, thanks for your answer! Cheers, Ingo =;-\> ---
**Author:** ![Ingo\_Schmidt](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/a88e57/32.png) [@Ingo\_Schmidt](https://www.ruby-forum.com/u/Ingo_Schmidt)\ **Post date:** [October 28, 2013, 10:57am UTC](https://www.ruby-forum.com/t/rewrite-last-using-variable/237165/4 "2013-10-28T10:57:44Z")
On Mon, Oct 28, 2013 at 09:36:20AM +0100, Ingo Schmidt wrote: Hi there, I was (partly) wrong when I said “”" > I guess that the URL encoding also takes place in the first case, but > here the client decodes the URL and thus everything is ok again. No; here what is sent to the client includes the bare ?. “”" Reading the code, the string does go through some uri-escaping and some uri-unescaping within nginx, and the end result is that a ? in $var remains a ? in what is written to the client. But it’s not a straight copy of the string. > > I believe it is intended to be “no”, for internal rewrites at least. > > Hmm, any reason why it might be intended? My guess? The value given must either be already uri-escaped, or not. And nginx chooses “not”. > Also, it would be nice if the docs could mention this, because I find it > unintuitive, if rewrite behaves differently depending on the rewrite type. If you presume that the docs are in the directory called “src”, then it’s mentioned there 😉 Anything "redirect"ed goes through an unescape. I expect that a correct clarifying patch to the docs will be welcomed, if you fancy writing one. > > You can do something like set $var “/url”; set $vararg “par=val”; > > rewrite ^ $var?$vararg last; > > Well, in my case that is exactly what I am trying to avoid, because my > > variable is set in a map and I would have to create two maps then, one > > with the URLs, the other with arguments. Generally in nginx, if there’s something that you can’t do in config, you can do it in a module you write. Possibly you can do it in config using one of the scripting language modules. (Usually, config is simpler in the short term.) Good luck with it, ## f Francis D. removed\_email\_address@domain.invalid