std::ctime(3)

💅 std::ctime(3) — C++ Standard Libary 💅

okay bestie, welcome to the std::ctime(3) page from the C++ Standard Libary. It’s giving “turn a std::time_t into a cute lil calendar string,” and we are keeping every detail exactly where it belongs. ✨

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🎀 NAME 🎀

std::ctime - std::ctime

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🦋 Synopsis 🦋

Defined in header <ctime>

char* ctime( const std::time_t* time );

Converts given time since epoch to a calendar local time and then to a textual representation, as if by calling std::asctime(std::localtime(time)). The resulting string has the following format:

Www Mmm dd hh:mm:ss yyyy\n

• Www — the day of the week (one of Mon, Tue, Wed, Thu, Fri, Sat, Sun).
• Mmm — the month (one of Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec).
• dd — the day of the month.
• hh — hours.
• mm — minutes.
• ss — seconds.
• yyyy — years.

The function does not support localization. 🫶

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🍓 Parameters 🍓

• time — pointer to a std::time_t object specifying the time to print.

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🫶 Return value 🫶

Pointer to a static null-terminated character string holding the textual representation of date and time. The string may be shared between std::asctime and std::ctime, and may be overwritten on each invocation of any of those functions. 😭

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💀 Notes 💀

This function returns a pointer to static data and is not thread-safe. In addition, it modifies the static std::tm object which may be shared with std::gmtime and std::localtime. POSIX marks this function obsolete and recommends std::strftime instead.

🚨 The behavior may be undefined for the values of std::time_t that result in the string longer than 25 characters (e.g. year 10000). Not me getting nervous at year 10000 💀

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🧪 Example 🧪

Run this code:

// Run this code

#include <cassert>
#include <cstring>
#include <ctime>
#include <iostream>

int main()
{
    std::time_t result = std::time(nullptr);
    std::cout << std::ctime(&result);

    char buffer[32];
    std::strncpy(buffer, std::ctime(&result), 26);
    assert('\n' == buffer[std::strlen(buffer) - 1]);
    std::cout << buffer;
}

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🌈 Possible output 🌈

Mon Oct 11 17:10:55 2021
Mon Oct 11 17:10:55 2021

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👀 See also 👀

• asctime — converts a std::tm object to a textual representation (function)
• strftime — converts a std::tm object to custom textual representation (function)
• put_time — formats and outputs a date/time value according to the specified format (C++11) (function template)
• C documentation for ctime

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source/version/date vibes: http://cppreference.com · 2024.06.10 · page std::ctime(3) — mwah, stay safe and don’t trust static buffers 💖