When executing CGI in the browser, an error occurs stating: /usr/bin/env: 'ruby': No such file or directory

#!/usr/bin/env ruby

# ...

Cause

The $PATH is not set.

#!/usr/bin/env bash

echo -ne "Content-type: text/html\n\n"
echo $PATH

Running this will display:

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

This shows that the directory containing Ruby is not present.

Solution

Set the Ruby path using :CGIPathEnv.

srv = WEBrick::HTTPServer.new({
   :DocumentRoot => "./site/",
   :Port => 8080,
   :CGIPathEnv => ENV["PATH"]
})