What exactly do you doubt about it?
It is perfectly valid 'C', and looks sensible - but what are you expceting it to do?

Your original comment is not correct:

// to set auxBuf with szInterface address 
sprintf(auxBuf,"%s",par->INPS->szInterface);

It does not set 'auxBuf' to the address of 'szInterface'; rather, it takes 'szInterface' to be the starting addressof a null-terminated string, and copies the string contents into 'auxBuf'

In this case, note that the "%s" is superfluous - you just need::

// print szInterface to auxBuf 
sprintf( auxBuf, par->INPS->szInterface );

(or use one of the string copy functions).

Note that this is all standard ANSI 'C' stuff - nothing specific to the 8051 at all