std::asctime
<ctime>
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 ofMon,Tue,Wed,Thu,Fri,Sat,Sun.Mmm- three-letter English abbreviated month name from time_ptr->tm_mon, one ofJan,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 character cannot be removed.
The function modifies static storage and is not thread-safe.
Contents
[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. 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.
[edit] Example
#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::asctime(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 2020年11月04日 00時45分01秒 strftime %a %b %e %H:%M:%S %Y 水 11月 4 00:45:01 2020
[edit] See also
(function template) [edit]