Remove trailing slash with mod_rewrite

I've tried every single example I could find, they all produce an internal server error. I have these rules set up (this works, no error):

Options +FollowSymLinks
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME}/index.php !-f
RewriteRule ^((/?[^/]+)+)/?$ ?q=$1 [L]

So if it's not an existing fi开发者_如何学编程le or an existing directory with an index.php we redirect. For instance, http://domain.com/foo/bar becomes http://domain.com/?q=foo/bar

Thing is, I want the trailing slash stripped. So take off the /? at the end of the rule. How do I make it so that http://domain.com/foo/bar/ becomes http://domain.com/foo/bar with a visible redirect first (fixing the client's URL), and only then the real, silent redirection to ?q=?

Everywhere I look I see this:

RewriteRule (.*)/$ $1 [R,L]

But it gives me a 500 error if I insert it before my rule.

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If foo/bar exists as a real directory, then the server will be redirecting the client to foo/bar/ (with the trailing slash). It has to do that in order for relative URLs to work correctly on the client. If you put in a rule to rewrite that back to foo/bar with a redirect then there will be a loop. An easy way to test if that's happening is to specify a path that doesn't exist at all (I assume from your index.php detection that the directory tree actually exists). The nonexistent path won't trigger the built-in redirect.

If I setup a similar set of rules to yours (plus the suggested slash-removal rule) I can see the difference between a directory that exists and one that doesn't. The ones that don't work as expected, the ones that do cause Firefox to say This page isn't redirecting properly. IE8 says something similar. Perhaps the Apache setup you're using can detect it and turns it into the 500 error?

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It looks like the simpler rewrite rule you mention at the end of your question should work. The problem is, the 500 error isn't really helpful in figuring out why it's not working. One way I've found useful in helping debug mod_rewrite errors is to enable it's logging. Add the following to your httpd.conf:

  RewriteLog "/usr/local/var/apache/logs/rewrite.log" 
  RewriteLogLevel 3 

Then try again, and look in the log to see what's going on. Once you're done, you can disable the log be setting the rewriteloglevel 0. See the mod_rewrite docs for details.

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Try this rule in front of your current rule:

RewriteRule (.*)/$ /$1 [R,L]

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Try these rules:

#prevent mod_dir from adding slash
DirectorySlash Off

#redirect /folder/ to /folder
RewriteCond %{THE_REQUEST} ^GET\s\S+/(\?\S+)?\s [NC]
RewriteRule ^(.*)/$ /$1 [R=301,L,QSA]

#internal redirect for directories
RewriteCond %{REQUEST_FILENAME} -d
RewriteCond %{REQUEST_URI} !/$
RewriteRule ^(.*)$ /$1/ [L]