First, I should probably state that this is being written in QNX, which is sorta UNIX, sorta POSIX, and sorta...something else. We're using it as a real-time microkernel for an embedded system (a real embedded system, not "embedded system" as Micros~1 would bastardize the term).

QNX's internal library supplies the QNX-specific function _cmdname(), which, according to its (typically terse) documentation:
The _cmdname() function determines the fullpath that the current process was invoked from and stores it in the buffer specified by buff.

Once I get this path, I can use the Unix standard basename() function to denude the path of all cruft except the actual file name. This provides he information I need.

My current question is: Is there a UNIX/POSIX equivalent of _cmdname() that you Masters know about?

BTW, to all, thanks for your help thus far!!!