CODEWITHSUNDEEP
c++time
aleio1
aleio1

Reputation: 94

Calling ctime twice produces same output with different inputs

I have this simple piece of code

#include <iostream>
#include <ctime>

using namespace std;

int main()
{

    time_t now = time(0);
    tm timeDate;
    strptime("2023-2-10 15:03","%Y-%m-%d %H:%M", &timeDate);

    time_t time_input = mktime(&timeDate);
    char* dt = ctime(&now);
    char* dt2 = ctime(&time_input);

    cout << "The local date and time is: " << dt << endl;
    cout << "The input date and time is: " << dt2 << endl;
    return 0;
}

that should print those two dates. But I receive the same date according to which is processed first.

The local date and time is: Fri Feb 10 15:03:00 2023
The input date and time is: Fri Feb 10 15:03:00 2023

or

The local date and time is: Mon Feb 13 12:32:17 2023
The input date and time is: Mon Feb 13 12:32:17 2023

Upvotes: 1

Views: 80

Answers (1)

Botje
Botje

Reputation: 30817

The ctime function is not reentrant, which means that you cannot safely call it multiple times and reuse the same output. Instead, use the ctime_r function which writes its output into a buffer you supply and then the times will be different.

Upvotes: 5

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