How to turn off the PROS stream identifier

Hello VEX forum

I’m trying to turn off the PROS stream identifier but I cannot seem too get the serctl() function working. I’ve attached the short section of test code I am using to try and understand how serctl() works.
I’m including apix.h in my header file and I am pretty sure I am using the action part of serctl() correctly.

Mostly I am confused by the extra_arg argument passed to the function. The PROS documentation describes it as the " little endian representation of the stream identifier (e.g. “sout” → 0x74756f73)". While I know that my stream identifier is “sout” (I have seen it in PuTTy) I don’t understand what form this argument should take.

Any help would be much appreciated.