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I'm having a bit of trouble with Nginx rewrites. I recently moved by blog over to a new engine, and the URL structure has changed. On my old blogging engine posts were located at a URL with the form http://$host/yyyy/mm/title.html however on the new engine they have the form http://$host/yyyy/mm/title/. The actual file that is being returned by the server resides at /yyyy/mm/title/index.html.

To make sure links in old posts still work I want to do a rewrite in Nginx that looks something like this:

rewrite ^/(\d\d\d\d)/(\d\d)/(.+)\.html$ $scheme://$host/$1/$2/$3/ permanent;

Unfortunately, this catches anything that ends with .html including index.html, so visiting a url of the form /(\d\d\d\d/)/(\d\d)/(.+)/ causes a redirect loop (nginx internally tries to use /$1/$2/$3/index.html, which redirects to /$1/$2/$3/, which redirects back to index.html, etc.).

I'd rather not use if statements if at all possible. Any ideas?

For reference the site is static, and my server config looks something like this (nothing fancy here):

server {
  listen      [::]:80;
  server_name blog.samwhited.com;
  root /var/www/blog.samwhited.com;
  charset utf-8;
  location ~* \.(js|css|png|jpg|jpeg|gif|ico)$ {
    expires max;
    log_not_found off;
  }
  error_page 404 /error/404.html;
  error_page 403 /error/403.html;
  location /error/ { internal; }
}

Here's a quick example of the expected redirect behavior:

http://blog.samwhited.com/2008/09/test.html -> http://blog.samwhited.com/2008/08/test/

It would also be great if index.html could be hidden. Nothing I've found online has worked. So this would also work:

http://blog.samwhited.com/2008/09/test/index.html -> http://blog.samwhited.com/2008/09/test/

share|improve this question
    
Is /2008/09/test.html the URL which the client is requesting, or is it the path on the webserver of the file? –  mgorven Jul 30 '12 at 2:09
    
Oops, misunderstood you, sorry. It is the URL which the client is requesting. It existed as a path on my old blogging engine (Blogger), however, on the new engine (Octopress) the URL is /2008/09/test/index.html (client requests /2008/09/test/). –  Sam Whited Jul 30 '12 at 2:29

1 Answer 1

up vote 2 down vote accepted

You pretty much need to use a if statement, but it's perfectly safe to do so if you only have rewrite directives inside it. You want to check the $uri variable since this includes modifications made by the index module.

if ($uri !~ /index\.html$) {
    rewrite ^/test/(\d\d\d\d)/(\d\d)/(.+)\.html$ /$1/$2/$3/ permanent;
}

To remove the index.html part you need to send a redirect, but only if the client specified index.html, and it wasn't added by the index module. This means we need another if statement to check this. We use the $request_uri variable here which is what the client actually sent.

if ($request_uri ~ /index\.html($|\?)) {
    rewrite ^(.*)/index\.html$ $1/ permanent;
}
share|improve this answer
    
Seems safe enough after re-reading the "ifisevil" (wiki.nginx.org/IfIsEvil) page. The first paragraph basically okays rewrites… no idea how I missed that. There's an unescaped full-stop in the second codeblock, but other than that works great — Thanks! –  Sam Whited Jul 30 '12 at 3:07
    
@SamWhited The if statement was implemented as part of the rewrite module and works fine within that. It was then abused to do non-rewrite things, which is where the brokenness comes in. –  mgorven Jul 30 '12 at 3:11
    
Makes sense. Any idea why Chrome would redirect to the SSL version of the site on occasion? Seems to only do it the second time I visit a URL. Is it better to rewrite to an absolute path? (eg. rewrite ^… $scheme://$host/$1/$2/$3/ permanent;) –  Sam Whited Jul 30 '12 at 3:19
    
@SamWhited No, that's not expected. nginx will use the current scheme and host if a relative URL is specified, so it's usually simpler to do that. –  mgorven Jul 30 '12 at 3:21
    
Alrighty; thanks for all your help! –  Sam Whited Jul 30 '12 at 3:23

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