.htaccess subdomains redirect is not working - .htaccess

Question

Ok, now I am lost.
I am trying to do a simple .htaccess redirect of subdomains to a specific folder on the server, meaning all
subdomain.mywebsite.com
will go to
www.mywebsite.com/s_subdomain
But for some reasons this doesn't work.
I have tried a lot of settings in .htaccess but for no good. Now in my .htaccess I have:
RewriteEngine on
Options +FollowSymLinks
Options +SymlinksIfOwnerMatch
RewriteCond %{HTTP_HOST} !^(www|ftp|mail)\.mywebsite\.com
RewriteCond %{HTTP_HOST} ^([^.]+)\.mywebsite\.com
RewriteRule (.*) /s_%1/$1 [L]
Are there any other settings, or is somethig I have missed?
PS. - I don't have access to http.conf. I have to do it using only .htaccess
Thanks!

Answer 1

This is just a "plain" rewrite (the browser won't see it). To redirect, add the R flag to your RewriteRule.
RewriteRule (.*) /s_%1/$1 [L,R]
The rest seems right, although I haven't tested it. For debugging you could consider RewriteLog, see http://httpd.apache.org/docs/2.0/mod/mod_rewrite.html#rewritelog

Answer 2

So, neither solution does work? Try something simple then.
RewriteEngine on
RewriteCond ${SERVER_NAME} ^(subdomain)\.yoursite\.com$ [nc]
RewriteRule ^(.*)$ http://www.yoursite.com/s_%1/$1 [L,R]
To test if your subdomain is handled correctly, create random.html file, place it where it should be read from, and try opening it via http://subdomain.yoursite.com/random.html. Then you can try some stuff like:
RewriteRule ^random.html - [F]
...and if that blocks access to file, try prepending
RewriteCond ${SERVER_NAME} ^subdomain\.yoursite\.com$ [nc]
to previous rule, to block access to that file, to make sure that rewrite engine is actually hitting your rules. That would target only desired subdomain (www.yoursite.com/random.html should work, but access via subdomain shouldn't).
Then if those rules work, it's just a matter of adding more stuff and see when it stops working.

Answer 3

RewriteRules are a bitch.
The following should work:
.htaccess:
RewriteCond ${SERVER_NAME} !^(www|ftp|mail)\.example\.com$
RewriteCond ${SERVER_NAME} !^([^.]+)\.example\.com$
RewriteRule .* redirect.php?to=%1
redirect.php
<?php
$desired_server_name = 'http://example.com';
$subdir = 's_' . $_GET['to'];
$url = $desired_server_name . '/' . $to . $_SERVER['REQUEST_URI'];
// Permanent redirects
header('HTTP/1.1 301 Moved Permanently');
// Or simple redirects:
header('HTTP/1.1 302 Found');
header('Location: '.$url);
?>
Works on my server (debian 4/apache 2).
Bonus: do not EVER use HTTP_HOST! See the following request:
HTTP/1.1 GET /foo/bar.php
Host: www.host.tld"><script>alert(/Hello/)</script
Connection: close
If you use $_SERVER['HTTP_HOST'] in your .php scripts to construct links or .htaccess rules for that matter and "www.host.tld" is the virtual-host or the only host configured for Apache, the XSS in the HTTP request header will be passed down unescaped.

Answer 4

We have a similar thing working on our Virtual Machines, where we redirect anything.usertld to a folder for that domain, that was in httpd.conf, tried in in the .htaccess and like yours it didn't work.
Tweaking it, this works for me (my VM occupies a tld called benb, but changing it to your domain should be fine):
RewriteCond %{HTTP_HOST} !^www\.benb
RewriteCond %{HTTP_HOST} ^(.*)\.benb
RewriteCond %{REQUEST_URI} !^/{0,1}s_
RewriteRule ^(.*)$ s_%1/$1 [L]
Also this captures all the text before the domain.. you should be able to change:
RewriteCond %{HTTP_HOST} ^(.*)\.benb
to
RewriteCond %{HTTP_HOST} ^([^.]+)\.benb
to handle just 1 level of subdomain. Also your other part about (www|ftp|mail) would work fine too.