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Defined in header <ctime> | ||
char* asctime(conststd::tm* time_ptr); | ||
Converts given calendar timestd::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 fromtime_ptr->tm_wday, one ofMon,Tue,Wed,Thu,Fri,Sat,Sun.Mmm - three-letter English abbreviated month name fromtime_ptr->tm_mon, one ofJan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec.dd - 2-digit day of the month fromtimeptr->tm_mday as if printed bysprintf using%2d.hh - 2-digit hour fromtimeptr->tm_hour as if printed bysprintf using%.2d.mm - 2-digit minute fromtimeptr->tm_min as if printed bysprintf using%.2d.ss - 2-digit second fromtimeptr->tm_sec as if printed bysprintf using%.2d.yyyy - 4-digit year fromtimeptr->tm_year+1900 as if printed bysprintf 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 bytime_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 |
| time_ptr | - | pointer to astd::tm object specifying the time to print |
Pointer to a static null-terminated character string holding the textual representation of date and time. The string may be shared betweenstd::asctime andstd::ctime, and may be overwritten on each invocation of any of those functions.
This function returns a pointer to static data and is not thread-safe. POSIX marks this function obsolete and recommends locale-dependentstd::strftime instead. Instd::locale("C") thestd::strftime format string"%c\n" will be an exact match tostd::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, whentimeptr->tm_wday ortimeptr->tm_mon are not within the expected ranges, or whentimeptr->tm_year exceedsINT_MAX-1990.
Some implementations handletimeptr->tm_mday==0 as meaning the last day of the preceding month.
#include <ctime>#include <iomanip>#include <iostream> int main(){conststd::time_t now=std::time(nullptr); for(constchar* 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
| converts astd::time_t object to a textual representation (function)[edit] | |
| converts astd::tm object to custom textual representation (function)[edit] | |
(C++11) | formats and outputs a date/time value according to the specified format (function template)[edit] |
C documentation forasctime | |
