How to trap the return error of system() ?

I'm writing a DOS program and is using system() to call an exe.
How do I trap the return error of the system() call?

Also is there any Sleep() function for a DOS program?

Thanks.

The system functions returns the error code :

int err = system("dir");

if this doesnt work, the return code anyhow is usualy stored in AX register right after the 'system' function returns.