Backticks returns "Bad File Descriptor" error with Apache


I wanted to run a command line program from Ruby. I used `(backticks) to
do this. It was successful if I run the program using Webrick but if I
run it using Apache 2.2.8, a “Bad File Descriptor” error is returned.

I needed to run svn list command to get the names of the files in a
target repository located in another machine. Using `(backticks) to run
the command gives me the output that i need.

Can anybody help tell me why (backticks) return this kind of error in Apache? Or is there a better way to run a command line in ruby that returns the same as the output of(backticks).

Please help.
Thank you very much.