How to rename a file in C .

rename.c

#include <stdio.h>
#include <stdlib.h>

/* A simple program demonstrating the
   C standard library , rename function .
   The rename function can rename files 
   and directories .*/
int
        main
            (int argc , char * argv [ ] ){

    char * prog_name = argv [0 ];
    char * from;
    char * to;

    if (argc != 3 ){
        fprintf(stderr , "Usage: %s from to.\n" , prog_name );
        exit (EXIT_FAILURE ); }

    from = argv [1 ];
    to = argv [2 ];

    if (rename (from , to ) == 0 ){
        printf ("The file %s , was renamed to %s\n" , from , to );
        return 0; }
    else {
        perror (NULL );
        exit (EXIT_FAILURE ); } }