这个正则表达式如何在htaccess中匹配

Question

I am trying to add trailing slash to a url. I have my own logic to do so but found another one on stackoverflow ( here ). Now the regex in this line

RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

apparently matches the RewriteRule for the url http://www.example.com/wp-admin .

What I first did was:

RewriteCond %{REQUEST_URI} /wp-admin$ [NC]
RewriteCond %{REQUEST_URI} !/+$
RewriteRule ^ %{ENV:proto}://%{HTTP_HOST}%{REQUEST_URI}/ [R=301,L]

So my question is how /wp-admin$ is similar to ^([_0-9a-zA-Z-]+/)?wp-admin$ ?

Answer 1

This is because leading slash is matched when you use RewriteCond %{REQUEST_URI} but current directory (relative to DocumentRoot ) is stripped when you use a pattern in RewriteRule in .htaccess file, which is a per directory directive.

Hence a leading slash is not matched in RewriteRule but is matched in RewriteCond .