The shell returns a wrong error code when it should return an error (on a bad file descriptor).
In this task, you will go through the whole work of fixing a bug: You have to analyze the situation, find the source of that bug in the code, and finally fix it.

In this task, you will also learn much about how a shell internally works. This will help you definetely if you want to do shell programming some day, or just want to dig more into the internals of file descriptors.

http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=47065