Actually, did you try using the Super Search to look for post raising similar questions? It's actually a good idea to do so, since many times you'll discover how much easier it is to read a readily available answer to a question very similar to yours that has long been posted on this site by someone else.

Actually, I did come across quite a few nodes with similar content. Here's a few posts you might want to look at:

• redirecting STDOUT (of a system call) to a var
• getting output from backticks
• How can I capture STDERR from an external command?

Hopefully these posts would explain a bit more ;-).

"There is no system but GNU, and Linux is one of its kernels." -- Confession of Faith