Difference between revisions of "cpp/chrono/c/ctime"

Latest revision as of 22:19, 19 August 2023

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.

[edit] Parameters

[edit] 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.

[edit] 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).

[edit] Example

#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;
}

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

[edit] See also