C/C++ :: Calling Files From Command Line?

In the following program I have one input .txt file of random words.

Example:

DOOR FLAG APPLE
CAR

I need to create output .txt file which will invert and print every word in the next row.

Example:

ROOD
GALF
ELPPA
RAC

When I run the program with command line arguments:

program.exe FILEINPUT.TXT FILEOUTPUT.TXT

I get the output same as input.

Here is the program:

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
void form(char **a,char **b,int n,char* (*t)(char *));
void invert_words(char *);
void form(char **a,char **b,int n,char* (*t)(char *)) {

[code].....