process name from process id

[R. Kannan]

The main objective is to get the program file name that resulted
in the process.

I have the pid for a process. I want to find out the name of
the program file that resulted in that process.


some_unknown_function ( getpid () ) => should return the name of the program
file that resulted int he calling process.

Thank you.

I want soemthing better than "ps | grep getpid ()" route. Direct callable
function. 

--kannan