The strftime() function is defined in <ctime> header file.
strftime() prototype
size_t strftime( char* str, size_t count, const char* format, const tm* time );
The strftime() function takes 4 arguments: str, count, format and time.
The date and time information pointed to by time is converted to a null-terminated multibyte character based on the value of format and is stored in the array pointed to by str. At most count bytes are written.
strftime() Parameters
- str: Pointer to the first element of the character array to store the result.
- count: Maximum number of bytes to write.
- format: Pointer to a null-terminated multibyte character string specifying the format of conversion. The format string consists of conversion specifier (beginning with % and optionally followed by E or O) and other ordinary characters.
The ordinary characters including the terminating null character are copied as it is to the output string.strftime() format specifiers Conversion Specifier Description Used Fields % Writes the character % n Writes newline character t Writes horizontal tab character Year Y Writes 4 digits of year, e.g. 2011 tm_year EY Writes 4 digits of year in locale's alternative representation tm_year y Writes last 2 digits of year, range [00, 99] tm_year Oy Writes the last 2 digits of year in locale's alternative representation tm_year Ey Writes year as offset from locale's alternative calendar period %EC (locale-dependent) tm_year C Writes first 2 digits of year, range [00,99] tm_year EC Writes name of the base year (period) in the locale's alternative representation, tm_year G Writes ISO 8601 week-based year, i.e. the year that contains the specified week. tm_year, tm_wday, tm_yday g Writes last 2 digits of ISO 8601 week-based year, i.e. the year that contains the specified week (range [00,99]). tm_year, tm_wday, tm_yday Month b Writes abbreviated month name, e.g. Jan tm_mon h Same as b tm_mon B Writes full month name, e.g. January tm_mon m Writes month as a decimal number, range [01,12] tm_mon Om Writes month using the locale's alternative numeric system tm_mon Week U Writes week of the year as a decimal number from 00 to 53 (Sunday is the first day of the week) tm_year, tm_wday, tm_yday OU Writes week of the year as by %U using the alternative numeric system tm_year, tm_wday, tm_yday W Writes week of the year as a decimal number from 00 to 53 (Monday is the first day of the week) tm_year, tm_wday, tm_yday OW Writes week of the year as by %W using the alternative numeric system tm_year, tm_wday, tm_yday V Writes ISO 8601 week of the year (range [01,53]). tm_year, tm_wday, tm_yday OV Writes week of the year, as by %V, using the alternative numeric system tm_year, tm_wday, tm_yday Day of the year/month j Writes day of the year as a decimal number, range [001,366] tm_yday d Writes day of the month as a decimal number, range[01,31] tm_mday Od Writes day of the month, as by %d, using the alternative numeric system tm_mday e Writes day of the month as a decimal number, range[1,31] tm_mday Oe Writes day of the month, as by %e, using the alternative numeric system tm_mday Day of the week a Writes abbreviated weekday name, e.g. Fri (locale dependent) tm_wday A Writes full weekday name, e.g. Friday (locale dependent) tm_wday w Writes weekday as a decimal number, range [0-6] (Sunday is 0) tm_wday Ow Writes weekday as by %w, using the alternative numeric system tm_wday u Writes weekday as a decimal number, where Monday is 1 (ISO 8601 format), range [1-7] tm_wday Ou Writes weekday as by %u, using the alternative numeric system tm_wday Hour, minute, second H Writes hour as a decimal number, range [00,23] tm_hour OH Writes hour as by %H, using the alternative numeric system tm_hour I Writes hour as a decimal number, range[01,12] tm_hour OI Writes hour as by %I, using the alternative numeric system tm_hour M Writes minute as a decimal number, range [00,59] tm_min OM Writes minute as by %M, using the alternative numeric system tm_min S Writes second as a decimal number, range [00,60] tm_sec OS Writes second as by %S, using the alternative numeric system tm_sec Other c Writes standard date and time string, e.g. Sun Oct 17 04:41:13 2010 (locale dependent) all Ec Writes locale's alternative date and time string all x Writes localized date representation (locale dependent) all Ex Writes locale's alternative date representation all X Writes localized time representation (locale dependent) all EX Writes locale's alternative time representation all D Equivalent to "%m/%d/%y" tm_mon, tm_mday, tm_year F Equivalent to "%Y-%m-%d" tm_mon, tm_mday, tm_year r Writes localized 12-hour clock time tm_hour, tm_min, tm_sec R Equivalent to "%H:%M" tm_hour, tm_min T Equivalent to "%H:%M:%S tm_hour, tm_min, tm_sec P Writes localized a.m. or p.m. (locale dependent) tm_hour z writes offset from UTC in the ISO 8601 format (e.g. -0545), or no characters if the time zone information is not available tm_isdst Z Writes time zone name or abbreviation, or nothing if the time zone information is not available (locale dependent) tm_isdst - time: The date and time information to convert.
strftime() Return value
- On success, the strftime() function returns the number of bytes written into the character array pointed to by str not including the terminating '\0'.
- If count was reached before the entire string could be stored, 0 is returned and the contents are undefined.
Example: How strftime() function works?
#include <ctime>
#include <iostream>
using namespace std;
int main()
{
time_t curr_time;
tm * curr_tm;
char date_string[100];
char time_string[100];
time(&curr_time);
curr_tm = localtime(&curr_time);
strftime(date_string, 50, "Today is %B %d, %Y", curr_tm);
strftime(time_string, 50, "Current time is %T", curr_tm);
cout << date_string << endl;
cout << time_string << endl;
return 0;
}
When you run the program, the output will be:
Today is April 21, 2017 Current time is 11:20:42
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