Unknown number of regex replacements, how? - regex

Question

I need to change a large number of URIs in the following way:
substitute %20 separators with dashes -,
substitute the old root with a new domain.
Examples:
/old_root/first/second.html -> http://new_domain.com/first/second
/old_root/first/second%20third.html -> http://new_domain.com/first/second-third
/old_root/first/second%20third%20fourth.html -> http://new_domain.com/first/second-third-fourth
The best I came up with using regex is to write as many pattern-replacement rules as the maximum number of %20 separators that can occur in my URIs:
old_root/(.*?)/(.*?)\.html -> http://new_domain.com/$1/$2
old_root/(.*?)/(.*?)%20(.*?)\.html -> http://new_domain.com/$1/$2-$3
old_root/(.*?)/(.*?)%20(.*?)%20(.*?)\.html -> http://new_domain.com/$1/$2-$3-$4
My question is: is it possible to obtain the same result using a single regular expression rule?
I thought I could use a two-step approach: first change all %20 separators to - and then use the rule old_root/(.*?)/(.*?)\.html -> http://new_domain.com/$1/$2/. However, I need to apply this rule in a .htaccess file as a RedirectMatch directive and, as far as I know, it is not possible to use two successive rules for the same redirect directive.

Answer 1

It turns out that Apache recursively applies all regex rules until they stop matching. Therefore, I am allowed to write two rules rather than one to solve my problem.
The following rules do what I was looking for, and more; I have tested them on my local Apache server and they work fine. Note that for them to work, you need to first turn on the rewrite engine by prepending
RewriteEngine on
Options +FollowSymlinks -MultiViews
in the local .htaccess file or in the global httpd.conf file.
Replace all spaces with hyphens
Replace both literal spaces and %20 with hyphens:
RewriteRule ^(.+)(\s|%20)(.+)$ /$1-$3 [R=301,NE,L]
Replace all apostrophes with hyphens
Replace all literal apostrophes and %60 with hyphens:
RewriteRule ^(.+)('|`|%60)(.+)$ /$1-$3 [R=301,NE,L]
Delete the trailing .html extension
RewriteRule (.+)\.html$ $1 [R=301,L]
Convert the last field in the URL to lower case
Convert the last field in the URL to lower case and prepend the new domain:
RewriteRule /whatever/(.*?)/(.*?)/(.*) http://new.domain.com/$1/$2/${lc:$3} [R=301,L]
Important: The lowercase conversion will only work if you include the following lines at the end of the Apache configuration file httpd.conf, which is usually located in the etc directory on the server:
RewriteEngine on
RewriteMap lc int:tolower
A last note: I recommend prepending each rule with a RewriteCond directive to restrict the field of application of the rule. For example, to apply the space-to-hyphens rule only to those URI that match a certain regex, you should write the following in your .htaccess file:
RewriteCond %{REQUEST_URI} regex_for_URIs
RewriteRule ^(.+)(\s|%20)(.+)$ /$1-$3 [R=301,NE,L]
where regex_for_URIs is the regular expression that the URI must match in order for the next RewriteRule to be applied; it can also be a simple string.

Answer 2

Well, you were almost done.
Problems
Don't return "%20" - We'll Use them as "delimiter" of parts of the path
Add condition on third & fourth group (because you might pass short URL i.e. your examples)
Solution
\/old_root\/(.*?)\/(\w*)(?:%20)?(\w*)?(?:%20)?(\w*)?\.html
See Demo
Explanation
(?:%20)? means "%20" is non catching group that can occurs 0 or 1 time.
Same logic applyies on possible 3rd & 4th part.