/* rot13 - Ein Prg zum decodieren von rot13 */

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


int main(int argc, char **argv)
{
    char *ABC;
    char *abc;
    int c;
    FILE *in, *out;

    if (argc != 3)
    {
        printf ("$VER: ROT13 1.0 (25.10.94)");
        printf ("\ngeschrieben von Helmut Kindler");
        printf ("\n\nAufruf: %s <infile> <outfile>\n", argv[0]);
        exit(0);
    }

    if ((in = fopen (argv[1], "r")) == NULL)
    {
        printf ("%s: Kann \"%s\" nicht zum Lesen öffnen\n", argv[0], argv[1]);
        exit(0);
    }

    if ((out = fopen (argv[2], "w")) == NULL)
    {
        printf ("%s: Kann \"%s\" nicht zum Schreiben öffnen\n", argv[0], argv[2]);
        fclose (in);
        exit(0);
    }

    ABC = "NOPQRSTUVWXYZABCDEFGHIJKLM";
    abc = "nopqrstuvwxyzabcdefghijklm";

    while ((c = fgetc (in)) != EOF)
    {
        //if (isupper(c))
        if ((c>='A') & (c<='Z'))
        {
            c = c - 'A';
            c = ABC[c];
        }
        //if (islower(c))
        if ((c>='a') & (c<='z'))
        {
            c = c - 'a';
            c = abc[c];
        }
        fprintf (out, "%c", c);
    }
    fclose (in);
    fclose (out);
}