Output adds wierd symbols when using a liberal string vs a variable

Question

i am doing a homework project which changes a string to morse code and it should take the output of "date" linux command

//Takes a char and converts it to morse code
char *morseEncode(char x)
{
    switch (x)
    {
    case 'a':
        return ".-";
    case 'b':
        return "-...";
  ....etc
        //numbers
    case '0':
        return ".-..";
  .... etc
        return "..-";

    //Others,mostly for date formats
    case ' ':
        return " ";
    case ':':
        return "---... ";
    case '-':
        return "-....- ";
    case '+':
        return ".-.-.";
    case '/':
        return "-..-.";

    //default
    default:
        printf("Error:Unknown Character\n");
    }
}


//gets date from linux terminal command date
char *getDate()
{
    char *res = (char *)malloc(100 * sizeof(char));
    FILE *fp = popen("date", "r");
    fgets(res, 100, fp);
    res[strlen(res) - 1] = '\0';
    pclose(fp);
    return res;
}


char *morseCode(char *s)
{
    char *str = (char *)malloc(sizeof(char) * strlen(s)+100);
    for (int i = 0; s[i] != '\0'; i++)
        strcat(str, morseEncode(s[i]));
    return str;
}

//changes a string to all lower letters since morseEncode function is for lower letters
char *strlwr(char *str)
{
    unsigned char *p = (unsigned char *)str;

    while (*p)
    {
        *p = tolower((unsigned char)*p);
        p++;
    }
        return str;
}

int main(int argc, char *argv[])
{
    char date[100]="thu jan  2 03:08:56 +04 2020"; //OUTPUT 1
    //char date[100];
    //strcpy (date,getDate()); //when this isnt commented OUTPUT 2
    printf("Morse Code of %s is:\t %s\n", date, morseCode(strlwr(date)));
    return 0;
}

The output 1 when i send the string is -......- .---.--. -. .-..------... .-..----... --.-.-. .-.-..-...--. -..-..-..-.. which is good,but when it gets it from the function

OUTPUT 2

Morse Code of thu jan 2 03:08:56 +04 2020 is:
$��-......- .---.--. -. .-..------... .-..----... --.-.-. .-.-..-...--. -..-..-..-..

As you can see it adds some weird symbols to the output

`char *str = (char *)malloc(sizeof(char) * strlen(s)+100);` <<-- malloc does not initialize the memory to all zeros. The strcat() expects a nul-terminated string. Performance-wise :there is also : https://www.joelonsoftware.com/2001/12/11/back-to-basics/ — wildplasser, Jan 01 '20 at 23:29
You should initialize the first character of `malloc`ed array to the null character in the function `morseCode` (just after `malloc` call): `str[0] = '\0';`, so that `strcat` works. Also, you must check the array bounds before `strcat` call; it is possible that you may overrun your array. — Lxer Lx, Jan 01 '20 at 23:40
btw the `asctime` function produces a date string that is *almost the same* as the one produced by date. — Antti Haapala -- Слава Україні, Jan 02 '20 at 00:10
string literals are `const char*` but you're returning `char*` — phuclv, Jan 02 '20 at 02:57

Output adds wierd symbols when using a liberal string vs a variable

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