Mod rewrite remove trailing slash but keep on directories - .htaccess

Question

So far my .htaccess is like this:
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} !^www\..+$ [NC]
RewriteRule ^ http://www.%{HTTP_HOST}%{REQUEST_URI} [R=301,L]
<FilesMatch "\.(htm|php|js|css|htc|png|gif|jpe?g|ico|xml|csv|txt|swf|flv|eot|woff|svg|ttf|pdf|gz)$">
RewriteEngine Off
</FilesMatch>
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule .*\.html$ index.php [L]
I would like to have url with trailing slash redirected to the one without. But the slash for directories should be kept.
Any help would be very appreciated!
UPDATE:
after some more Google research i assembled some working solution for me. Both rewriting for removing trailing slash and redirect for www are working.
RewriteRule ^(.+)/$ http://%{HTTP_HOST}/$1 [L,R=301]
RewriteCond %{HTTP_HOST} ^rudolfapotheke.de$ [NC]
RewriteRule ^(.*) http://www.%{HTTP_HOST}/$1 [L,R=301]

Answer 1

First, I would change your FilesMatch to a RewriteCond
RewriteCond %{REQUEST_FILENAME} !\.(?:htm|php|js|css|htc|png|gif|jpe?g|ico|xml|csv|txt|swf|flv|eot|woff|svg|ttf|pdf|gz)$
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php [L]
and simplify the pattern for the next RewriteRule
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule \.html$ index.php [L]
or put the two rules together and test just for
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php [L]
and finally the rule for removing the trailing slash
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)/$ $1 [R,L]

Answer 2

To redirect those with trailing slash, you need to check if the path is a directory with a RewriteCond and then include a RewriteRule if the filename matchs /$
So it would look something like this:
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)/$ $1 [R=permanent,L]