Starting an application from GDB prompt

Hello All,

I have an application that is to be debugged using GDB. So I can use
the standard gdb <app_name> and enter into the gdb prompt and then
start my application,make it to crash and get the backtrace.

But the problem is that the application to be debugged is driven by
another application which has to be started after this and from the
same shell session. So my problem is once I am at the gdb prompt, I
don't know how to start my other application(which is not needed to be
debugged) which driver the actual application to be debugged.

Any thoughts how to get this done ?