Reverse in c.

FileReverse.c

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


int main( int argc, char **argv )
{
    FILE *in_file;
    char ch;
    int len;
    
    if( 2 != argc )
    {
        printf("Error: wrong number of arguments.");
        return 1;
    }
    
    // Apro il file:
    in_file = fopen(argv[1], "r");
    if(NULL != in_file)
    {
        perror("fopen:");
    }
    
    //Mi sposto alla fine
    fseek(in_file, 0, SEEK_END);
    
    //Trovo il numero di caratteri
    len = ftell (in_file);
    
    fseek(in_file, -1L, SEEK_CUR);
    
    while(len > 0)
    {
        ch = fgetc(in_file);
        fseek(in_file, -2L, SEEK_CUR);
        printf("%c", ch);
        len--;
    }

    return 0;
}