Redirect URI Path to Subdomain With Regex

Question

How can i redirect this URI to subdomain with RegEx? I need to redirect only this file.php with query string.

https://url.com/file.php?url=anystring
to
https://sub.url.com/file.php?url=anystring

i tried this, didn't work.

RewriteEngine On
RewriteCond %{REQUEST_URI}  ^\/file\.php$ 
RewriteCond %{QUERY_STRING} ^url=([a-z]*) 
RewriteRule ^ https://sub.%1%{REQUEST_URI} [R=301,L]

Answer 1

RewriteEngine On
RewriteCond %{REQUEST_URI}  ^/file.php$ 
RewriteCond %{QUERY_STRING} ^url=([a-z]*) 
RewriteRule ^(.*)$ https://sub.url.com/file.php [R=301,L]