Strftime() in C

Introduction:

The time.h header file contains a definition for the strftime function. Its purpose is to generate and save a string in the specified format. It makes use of the time values kept in a specific tm struct.

Syntax

The syntax for the strftime() method is provided below.

Size_tstrftime(char *str, size_tmaxsize, const char *format, const struct tm *timeptr)

The parameters or arguments used:

Str-

It is a pointer to the target array where the copied C string from the result is stored.

Maxsize −

It is the maximum character count that can be copied to str.

Format −

It is the C string that can contain any mixture of alphabetic and numeric characters as well as unique format specifiers. The function replaces these format specifiers with the correct values to represent the time supplied in tm.

These are the format specifiers:

Specifier	Replaced by	Example
%a	Weekday's abbreviated name	Mon
%A	Weekday's full name	Monday
%b	Shortened month name	Feb
%B	Month's full name	February
%c	Display of time and date	Sun Aug 19 02:56:02 2012
%d	(01-31) Day of the month	19
%H	Hour (00-23) in 24-hour format	14
%I	(01-12) hour in a 12-hour format	05
%j	Date (from 001 to 366)	231
%m	Month expressed as a decimal (01-12)	08
%M	(Minute 00:59)	55
%p	AM or PM time zone	PM
%S	(00-61)second	02
%U	Week number, with the first Sunday serving as week one's first day (00-53)	33
%w	Sunday is represented by the number 0 (0-6) on a weekday.	4
%W	Week number, with the first Monday serving as week one's first day (00-53)	34
%x	Representing dates	08/19/12
%X	Representation of time	02:50:06
%y	Last two digits of the year (00-99)	01
%Y	Year	2012
%Z	Name or shorthand for the time zone	CDT
%%	A% symbol	%

The timeptr -

It is a pointer to a tm structure that holds the components of a calendar time, as seen below.

Struct tm {
   Int time_sec;         /* seconds, from 0 to 59          */
   Int time_min;         /* minutes, 0 to 59.           */
   Int time_hour;        /* hours between 0 and 23             */
   Int time_mday;        /* range of 1 to 31 days in the month  */
   Int time_mon;         /* range from 0 to 11 months             */
   Int time_year;        /* how many years have passed since 1900   */
   Int time_wday;        /* weekday with a value between 0 and 6   */
   Int time_yday;        /* has a value between 0 and 365.  */
   Int time_isdst;       /* daytime extending hours         */	
};

Return Value

The total number of characters copied to str (excluding the ending null-character) is returned if the resulting C string can be written in fewer than size characters (which includes the terminating null-character), in which case zero is returned.

Example

The strftime() method is used in the example below.

#include <stdio.h>
#include <time.h>

int main () {
time_trawtime;
   struct tm *info;
   char buffer1[100];

time( &rawtime );

   Info = localtime( &rawtime );

strftime(buffer1,80,"%x - %I:%M%p", info);
printf("The Formatted date & time is : |%s|\n", buffer1 );

return(0);
}

Output:

The Formatted date & time is : |06/03/23 - 05:17PM|

Example:2

// A C program that demonstrates how strftime() works
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#define Size 50

int main ()
{
	time_tt ;
	struct tm *tmp ;
	char MY_TIME[Size];
	time( &t );
	
	//In order to fill a tm structure with values that correspond to the local time, localtime() uses the time pointed to by t.
	
	tmp = localtime( &t );
	
	// displaying time with strftime
	strftime(MY_TIME, sizeof(MY_TIME), "%x - %I:%M%p", tmp);
	
	printf("The Formatted date & time : %s\n", MY_TIME );
	return(0);
}

Output:

The Formatted date &time : 06/03/23 - 05:42PM

Explanation:

Here all the essential header files (stdlib.h, stdio.h, and time.h) are added. The size of the character array MY_TIME is defined by the Size constant, which will store the formatted date and time.

To obtain the current time in seconds since the Unix epoch (January 1, 1970), the time() function is used with the address of t as an argument. The address of t is passed as an argument when the localtime() method is called. The MY_TIME array contains the formatted date and time.

Using printf(), the formatted date and time are displayed on the terminal. The main() function comes to a close, and the program returns 0 to signify that it ran successfully.

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