linux strftime的格式

<ctime>

size_t strftime ( char * ptr, size_t maxsize, const char * format, const struct tm * timeptr );

Format time to string

Copies into ptr the content of format, expanding its format tags into the corresponding values as specified bytimeptr, with a limit of maxsize characters.

Parameters

ptr

Pointer to the destination array where the resulting C string is copied.

maxsize

Maximum number of characters to be copied to ptr.

format

C string containing any combination of regular characters and special format specifiers. These format specifiers are replaced by the function to the corresponding values to represent the time specified in timeptr. They all begin with a percentage (%) sign, and are:

specifier	Replaced by	Example
%a	Abbreviated weekday name *	Thu
%A	Full weekday name *	Thursday
%b	Abbreviated month name *	Aug
%B	Full month name *	August
%c	Date and time representation *	Thu Aug 23 14:55:02 2001
%d	Day of the month (01-31)	23
%H	Hour in 24h format (00-23)	14
%I	Hour in 12h format (01-12)	02
%j	Day of the year (001-366)	235
%m	Month as a decimal number (01-12)	08
%M	Minute (00-59)	55
%p	AM or PM designation	PM
%S	Second (00-61)	02
%U	Week number with the first Sunday as the first day of week one (00-53)	33
%w	Weekday as a decimal number with Sunday as 0 (0-6)	4
%W	Week number with the first Monday as the first day of week one (00-53)	34
%x	Date representation *	08/23/01
%X	Time representation *	14:55:02
%y	Year, last two digits (00-99)	01
%Y	Year	2001
%Z	Timezone name or abbreviation	CDT
%%	A % sign	%

* The specifiers whose description is marked with an asterisk (*) are locale-dependent.

timeptr

Pointer to a tm structure that contains a calendar time broken down into its components (see tm).

Return Value

If the resulting C string fits in less than maxsize characters including the terminating null-character, the total number of characters copied to ptr (not including the terminating null-character) is returned.
Otherwise, zero is returned and the contents of the array are indeterminate.

Portability

This description corresponds to the C++ version of this function (which is the same as in the ISO-C Standard of 1990). C compilers may support additional specifiers and modifiers for the format parameter of this function, which are not described here.

Example

/* strftime example */
#include <stdio.h>
#include <time.h>

int main ()
{
  time_t rawtime;
  struct tm * timeinfo;
  char buffer [80];

  time ( &rawtime );
  timeinfo = localtime ( &rawtime );

  strftime (buffer,80,"Now it's %I:%M%p.",timeinfo);
  puts (buffer);
  
  return 0;
}

Example output:

Now it's 03:21PM.

See also

ctime

Convert time_t value to string (function)

asctime

Convert tm structure to string (function)