Odd characters in string output C++

Question

I keep getting this odd problem where these characters appear in my char array called day[3]. My goal is to use the computers clock and get the date and time. I put that into a string called dayHolder and want to just add the day it to a char array called day. But when I do this it gets a lot of odd characters. I understand that the string should end with '\0' but cant seem to get day to just display "Fri"....

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <time.h>
#include <string>


using namespace std;

int main() {
    // Functions
    functions myFunc;

    //Variables + installations  
    string dayHolder;
    char day[3];
    char whitespace = ' ';
    time_t current = time(0);

    dayHolder = ctime(&current);


    for (int i = 0; i < 3; i++)
    {
        day[i] = dayHolder[i];
    }



    cout << ctime(&current) << endl;
    cout << dayHolder << endl;
    cout << day << endl;


    return 0;
}

enter image description here

So what can I do to fix this problem? I am sure its something simple that I am overlooking so any advise or suggestions would be appreciated thanks.

Since you understand that string must be null terminated. Then why you don't char day[4] ... day[3] = '\0';? — Dimitrios Bouzas
– Dimitrios Bouzas, Commented Sep 12, 2014 at 20:18

AlexD · Accepted Answer · 2014-09-12 20:29:46Z

3

char day[3] is not zero-terminated.

Try

char day[4];

....

for (int i = 0; i < 3; i++)
{
    day[i] = dayHolder[i];
}
day[3] = 0; // or '\0' as @DeepBlackDwarf suggested

Or, alternatively

string day = dayHolder.substr(0, 3);

edited Sep 12, 2014 at 20:29

answered Sep 12, 2014 at 20:18

AlexD

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2 Comments

T.Malo Over a year ago

Hey, wow that worked! I am going to look it up after I post this but I thought that char arrays start at base 0. So in the case of Fri 0 = F, 1 = r, 2 = i, 3 = null i.e \0. Is how does making the memory of the array 4 fix this?

AlexD Over a year ago

There is no 3. day[3] declares an array or three elements, with indices 0, 1, 2. In addition, array is not initialized by default (but see the answer of fbrereto).

BlackDwarf · Accepted Answer · 2014-09-12 20:19:27Z

2

You have to add an extra '\0' character at the end of the string, ie declare a char day[4] and assign the last char with day[3] = '\0'.

answered Sep 12, 2014 at 20:19

BlackDwarf

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Comments

fbrereto · Accepted Answer · 2014-09-12 20:22:26Z

2

You need to null-terminate, as has been mentioned. First you'll need to add another byte for the null. Another option is to zero out the buffer initially:

char day[4] = { 0 };

As long as you don't overwrite day[3] that value will stay 0 and the string will stay a valid c-string.

answered Sep 12, 2014 at 20:22

fbrereto

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2 Comments

Bill Lynch Over a year ago

Except that they write 3 characters in, so unless the buffer is larger you still won't have a terminating null character.

Void - Othman Over a year ago

One more for the null terminator: char day[4] = { 0 }

macfij · Accepted Answer · 2014-09-12 20:29:58Z

1

That happens because cout keeps on writing to stdout until it meets a null terminator, hence the garbage values. Since you are using a C-style string, you should always remember to include an additional space in order to null terminate your string (e.g. you want to store 3 chars, so buffer should have size of 4). Others already mentioned that you need a bigger buffer and put there a \0 at the end.

answered Sep 12, 2014 at 20:29

macfij

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Comments

Dimitrios Bouzas · Accepted Answer · 2014-09-12 20:44:40Z

1

Why don't you use std::string since you've already included string header:

time_t current = time(0);
string dayHolder = ctime(&current);
string day(dayHolder.begin(), dayHolder.begin() + 3);

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answered Sep 12, 2014 at 20:44

Dimitrios Bouzas

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