Using Apache httpd 2.4 mod_rewrite

I recorded this here because I couldn’t find a good recommendation for a rewrite rule to put in the .htaccess file in the document root of my websites at sphaerula.com and conradhalling.com.

My issue was that I built my Jekyll sites on my MacBook Pro and synchronized them to my web hosting accounts using the rsync utility. I synchronized the files into the blog/ subdirectory to avoid overwriting or deleting any files in the document root directory. But I wanted my blog to appear when a user went to my website.

My use case was, for example, that the user would enter https://sphaerula.com into their web browser, but the website would redirect them to https://sphaerula.com/blog/. I needed a rewrite rule to put in the .htaccess file in the document root folder that would accomplish this.

I spent an afternoon of trial and error, reading many stackoverflow entries, blog pages, and even the Apache httpd documentation, but I could not find a formula that actually worked. What appeared to be the exact solution I needed was presented in the Moved DocumentRoot section of the Apache httpd documentation, but it did not work!

After intense debugging on my Mac using LogLevel alert rewrite:trace3 in my Apache httpd configuration file, as recommended in the Apache Module mod_rewrite | Logging section, I figured out a rewrite rule that worked:

RewriteEngine on
RewriteRule ^$ /blog/ [R]

For an .htaccess file at the document root, the RewriteEngine was working in the per-directory context. The Apache httpd documentation stated:

In per-directory context (Directory and .htaccess), the Pattern is matched against only a partial path, for example a request of “/app1/index.html” may result in comparison against “app1/index.html” or “index.html” depending on where the RewriteRule is defined.

This rewrite rule was pretty simple. The syntax for a rewrite rule was RewriteRule Pattern Substitution [flags].

Pattern: Since the path for the document root was /, but in per-directory context, the leading / was stripped off, the rewrite rule received an empty string. The pattern for matching an empty string was ^$.

Substitution: The substitution string was /blog/ with the leading and trailing / characters (because that was what worked empirically).

Flags: Finally, the [R] flag indicated a redirect.

Surrounding the pattern and substitution strings with double quote characters broke the rewrite rule (despite many examples in the documentation using quoted strings).

I installed this .htaccess file in the document root directory of each of my websites, and it worked correctly to redirect HTTP requests to the blog/ subdirectory, as desired.