C Library Function - strftime()
Description
The C library function sizet strftime(char *str, sizet maxsize, const char *format, const struct tm *timeptr) formats the time represented by the structure timeptr according to the formatting rules defined in format and stores it in str.
Declaration
Here is the declaration for the strftime() function.
size_t strftime(char *str, size_t maxsize, const char *format, const struct tm *timeptr)
Parameters
str -- This is a pointer to the destination array where the resulting C string is copied.
maxsize -- This is the maximum number of characters to be copied to str.
format -- This is a C string containing any combination of regular characters and special format specifiers. These format specifiers are replaced by the function with the corresponding values representing the time specified in the tm structure. The format specifiers are:
| Specifier | Replaced by | Example |
|---|---|---|
| %a | Abbreviated weekday name | Sun |
| %A | Full weekday name | Sunday |
| %b | Abbreviated month name | Mar |
| %B | Full month name | March |
| %c | Date and time representation | Sun Aug 19 02:56:02 2012 |
| %d | Day of the month (01-31) | 19 |
| %H | Hour in 24-hour format (00-23) | 14 |
| %I | Hour in 12-hour format (01-12) | 05 |
| %j | Day of the year (001-366) | 231 |
| %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 of the year, with the first Sunday as the first day of the first week (00-53) | 33 |
| %w | Weekday as a decimal number, with Sunday as 0 (0-6) | 4 |
| %W | Week number of the year, with the first Monday as the first day of the first week (00-53) | 34 |
| %x | Date representation | 08/19/12 |
| %X | Time representation | 02:50:06 |
| %y | Year, last two digits (00-99) | 01 |
| %Y | Year | 2012 |
| %Z | Time zone name or abbreviation | CDT |
| %% | A % character | % |
- timeptr -- This is a pointer to a tm structure that contains a calendar time broken down into its components:
struct tm { int tm_sec; /* Seconds, range 0 to 59 */ int tm_min; /* Minutes, range 0 to 59 */ int tm_hour; /* Hours, range 0 to 23 */ int tm_mday; /* Day of the month, range 1 to 31 */ int tm_mon; /* Month, range 0 to 11 */ int tm_year; /* Years since 1900 */ int tm_wday; /* Day of the week, range 0 to 6 */ int tm_yday; /* Day of the year, range 0 to 365 */ int tm_isdst; /* Daylight saving time */ };
Return Value
If the resulting C string is less than size characters long (including the terminating null character), the total number of characters (excluding the null character) copied to str is returned; otherwise, zero is returned.
Example
The following example demonstrates the use of the strftime() function.
#include <stdio.h>
#include <time.h>
int main ()
{
time_t rawtime;
struct tm *info;
char buffer[80];
time( &rawtime );
info = localtime( &rawtime );
strftime(buffer, 80, "%Y-%m-%d %H:%M:%S", info);
printf("Formatted date & time : |%s|\n", buffer );
return(0);
}
Let's compile and run the above program, which will produce the following result:
Formatted date & time : |2018-09-19 08:59:07|