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I'm stuck (apologies if I just didn't find the answer to this - I did read a number of answers and didn't see a solution to this problem).

I have a line in my code to print "ciphertext:" before the output of the program. However, my output will correctly create one word and then wrap around to start overwriting the "ciphertext:". For example - keyword is bacon, plaintext is Meet me at the park at eleven am. The output should be: ciphertext: Negh zf av huf pcfx bt gzrwep oz My output is: `wep ozext: Negh It works if I add a \n after every letter...

Any help would be greatly appreciated. I am very new to this, so my code probably has quite a number of errors.

#include <cs50.h>
#include <ctype.h>
#include <stdio.h>
#include <string.h>

// giving the program a heads-up that a function will be defined later
int shift(char c);

// gettting an argument in the command line
int main(int argc, string argv[])
{
    // checking the number of words in command line
    if (argc==2)
{
    // creating a constant for using the second word in command line
    const int KEY = 1;

    // string length of argv1
    int w = strlen(argv[KEY]);

    // loop 1 to check for digits in the second argument of the command line
    for (int z = 0; z < w; z++)
    {
        // checking for digits
        if isdigit(argv[KEY][z])
        {
            printf("Usage: ./vigenere keyword\n");
            return 1;
        }
    }

    // getting the text to cipher
    string s = get_string("plaintext: ");

    // Ciphertext will be shown here
    printf("ciphertext: ");

    //Putting the string length here because it was causing problems with the output
    int j = strlen(s);

    // loop 2 - let's cipher that text by looping the key and the plaintext
    for (int x = 0, i = 0; i < j && x < w; i++)
    {
        // Creating the integer for converting
        int d = (int) s[i];

        // Wrapping around the key loop
        if (x < (w-1))
        {
            // numeric value to shift the key
            int v = shift(argv[KEY][x]);

            // turning character into integer
            if isupper(s[i])
            {
                int up = (((d - 'A') + v) % 26) + 'A';
                printf("%c", (char) up);

                // Wrapping around the key by going up one in the counter
                x++;
            }

            // Change lower case by X
            else if islower(s[i])
            {
                int low = (((d - 'a') + v) % 26) + 'a';
                printf("%c", (char) low);

                // Wrapping around the key by going up one in the counter
                x++;
            }

            // Non changed characters
            else
            {
                printf("%c", (char) d);
            }
        }

        // second part of the loop to wrap back to zero
        else
        {
            // numeric value to shift the text
            int v = shift(argv[KEY][x]);

            // turning character into integer
            if isupper(s[i])
            {
                int up = (((d - 'A') + v) % 26) + 'A';
                printf("%c", (char) up);

                // Wrapping around the key by going back to zero
                x = 0;
            }

            // Change lower case by X
            else if islower(s[i])
            {
                int low = (((d - 'a') -+ v) % 26) + 'a';
                printf("%c", (char) low);

                // Wrapping around the key by going back to zero
                x = 0;
            }

            // Non changed characters
            else
            {
                printf("%c", (char) d);
            }
        }
    }
    printf("\n");
    return 0;
}
else
{
    printf("Usage: ./vigenere keyword\n");
}
}


int shift(char c)
{
if isupper(c)
{
    int u = c - 'A';
    printf("%c", (char) u);
    return u;
}
else
{
    int l = c - 'a';
    printf("%c", (char) l);
    return l;
}
}
1

You've got a few issues, but the one most affecting you is that you are printing values in your shift function that aren't printable. You shouldn't be printing anything in your shift function. What happens is you end up with, say, a value of 8 (backspace) or a value of 13 (carriage return), which, when printed to the terminal, do exactly that. You end up seeing your text overwritten.

| improve this answer | |
  • Thank you! This fixed that issue. Now to fix the rest. – mallhair Mar 27 '19 at 19:23

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