How to use shell environment variable in GDB?

[Weihua JIANG]

E.g. I have a shell environment variable CSR which points to a deep
directory. Now I hope to load the executable file using below command:
         file  $CSR/bin/aaa
But, since GDB can't recognize this environment variable, it can't
load the executable file.

How can I use BASH environment variable in GDB?

Thanks
Weihua