title: Same process id for exec in ruby script
body: <p>Is there anyone know the implementation of exec by JRuby implementation. </p>
  
  <p>I have two simple rubys scripts: Test.rb calls another called.rb via exec, as below: </p>
  
  <pre><code>//Test.rb
  #!/usr/bin/env jruby
  sleep 10
  puts "hello 1 " 
  exec  "./called.rb"
  puts "hello 2"
  
  //called.rb
  #!/usr/bin/env jruby
  puts "called a "
  sleep 10
  puts "called b
  </code></pre>
  
  <p>After executing ./test.rb, I ps java processes during execution of Test.rb and called.rb. The result is: </p>
  
  <pre><code>shijiex   6129  9987 10 22:21 pts/2    00:00:00 java -client -Djruby.memory.max=500m -Djruby.stack.max=1024k -Xmx500m -Xss1024k -Djffi.boot.library.path= -Xbootclasspath/a:/usr/lib/jruby//lib/jruby.jar -classpath : -Djruby.home=/usr/lib/jruby/ -Djruby.lib=/usr/lib/jruby//lib -Djruby.script=jruby -Djruby.shell=/bin/sh org.jruby.Main ./test.rb
  shijiex   6129  9987  4 22:21 pts/2    00:00:00 java -client -Djruby.memory.max=500m -Djruby.stack.max=1024k -Xmx500m -Xss1024k -Djffi.boot.library.path= -Xbootclasspath/a:/usr/lib/jruby//lib/jruby.jar -classpath : -Djruby.home=/usr/lib/jruby/ -Djruby.lib=/usr/lib/jruby//lib -Djruby.script=jruby -Djruby.shell=/bin/sh org.jruby.Main ./test.rb
  </code></pre>
  
  <p>My understanding is that exec should invoke another Jruby process but i have not saw it. 
  Does anyone know reason? </p>