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std::asctime(3) C++ Standard Libary std::asctime(3) NAME std::asctime - std::asctime Synopsis Defined in header <ctime> char* asctime( const std::tm* time_ptr ); Converts given calendar time std::tm to a textual representation of the following fixed 25-character form: Www Mmm dd hh:mm:ss yyyy\n * Www - three-letter English abbreviated day of the week from time_ptr->tm_wday, one of Mon, Tue, Wed, Thu, Fri, Sat, Sun. * Mmm - three-letter English abbreviated month name from time_ptr->tm_mon, one of Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec. * dd - 2-digit day of the month from timeptr->tm_mday as if printed by sprintf using %2d * hh - 2-digit hour from timeptr->tm_hour as if printed by sprintf using %.2d * mm - 2-digit minute from timeptr->tm_min as if printed by sprintf using %.2d * ss - 2-digit second from timeptr->tm_sec as if printed by sprintf using %.2d * yyyy - 4-digit year from timeptr->tm_year + 1900 as if printed by sprintf using %4d The behavior is undefined if any member of *time_ptr is outside its normal range The behavior is undefined if the calendar year indicated by time_ptr->tm_year has more than 4 digits or is less than the year 1000. The function does not support localization, and the newline charac- ter cannot be removed. The function modifies static storage and is not thread-safe. Parameters time_ptr - pointer to a std::tm object specifying the time to print 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. Notes This function returns a pointer to static data and is not thread- safe. POSIX marks this function obsolete and recommends locale-dependent std::strftime instead. In std::locale("C") the std::strftime format string "%c\n" will be an exact match to std::asctime output, while in other locales the format string "%a %b %e %H:%M:%S %Y\n" will be a potentially closer but not always exact match. POSIX limits undefined behaviors only to the cases when the output string would be longer than 25 characters, when timeptr->tm_wday or timeptr->tm_mon are not within the expected ranges, or when timeptr->tm_year exceeds INT_MAX-1990. Some implementations handle timeptr->tm_mday==0 as meaning the last day of the preceding month. Example // Run this code #include <ctime> #include <iomanip> #include <iostream> int main() { const std::time_t now = std::time(nullptr); for (const char *localeName : {"C", "en_US.utf8", "de_DE.utf8", "ja_JP.utf8" }) { std::cout << "locale " << localeName << ":" "\n" << std::left; std::locale::global(std::locale(localeName)); std::cout << std::setw(40) << " asctime" << std::asc- time(std::localtime(&now)); // strftime output for comparison: char buf[64]; if (strftime(buf, sizeof buf, "%c\n", std::localtime(&now))) { std::cout << std::setw(40) << " strftime %c" << buf; } if (strftime(buf, sizeof buf, "%a %b %e %H:%M:%S %Y\n", std::localtime(&now))) { std::cout << std::setw(40) << " strftime %a %b %e %H:%M:%S %Y" << buf; } std::cout << '\n'; } } Possible output: locale C: asctime Wed Nov 4 00:45:01 2020 strftime %c Wed Nov 4 00:45:01 2020 strftime %a %b %e %H:%M:%S %Y Wed Nov 4 00:45:01 2020 locale en_US.utf8: asctime Wed Nov 4 00:45:01 2020 strftime %c Wed 04 Nov 2020 12:45:01 AM UTC strftime %a %b %e %H:%M:%S %Y Wed Nov 4 00:45:01 2020 locale de_DE.utf8: asctime Wed Nov 4 00:45:01 2020 strftime %c Mi 04 Nov 2020 00:45:01 UTC strftime %a %b %e %H:%M:%S %Y Mi Nov 4 00:45:01 2020 locale ja_JP.utf8: asctime Wed Nov 4 00:45:01 2020 strftime %c 20201104 004501 strftime %a %b %e %H:%M:%S %Y 11 4 00:45:01 2020 See also ctime converts a std::time_t 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) http://cppreference.com 2022.07.31 std::asctime(3)
NAME | Synopsis | Parameters | Return value | Notes | Example | Possible output: | See also
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