Check value of system function

I want to find the return value of the mount command which is passed into the system function using the C language. How can I do this?

For example:

printf("return val = %d",WEXITSTATUS(system(mount /dev/sda /media/mmcblk0)));

But every time it gives me 255 as the value.

How can I find return code fired by my mount commandor any other solution?

NOTE: I have included header files properly