bst in postorder to file algorithm?

i need to create a function (inside bst.h) that will save the contents of the bst (before deleting the whole bst when the program would be terminating) in a file, containing the numbers in the bst in postorder..

can anyone share an algorithm on how to implement this?

You know what postorder traversal means, right? Now instead of "print" you have "write to file".

yeah i get it.thanks!