How to get full path of a file just by giving the filename in C?

Suppose I have a file path as C:\Sample\example.txt.

how can full path of the file be retrieved (the file can be in an开发者_Python百科y directory) just by giving the filename i.e., example.txt in C ?

---

get the source for the "find" command from the (i think) gnu package (or a linux source distribution), and copy the appropriate passages for you platform.