STRFTIME(3)
NAME
strftime - format date and time
SYNOPSIS
#include <<time.h>>
size_t strftime(char *s, size_t max, const char *format,
const struct tm *tm);
DESCRIPTION
The strftime() function formats the broken-down time tm
according to the format specification format and places
the result in the character array s of size max.
Ordinary characters placed in the format string are copied
to s without conversion. Conversion specifiers are intro-
duced by a `%' character, and are replaced in s as fol-
lows:
%a The abbreviated weekday name according to the cur-
rent locale.
%A The full weekday name according to the current
locale.
%b The abbreviated month name according to the current
locale.
%B The full month name according to the current
locale.
%c The preferred date and time representation for the
current locale.
%d The day of the month as a decimal number (range 01
to 31).
%H The hour as a decimal number using a 24-hour clock
(range 00 to 23).
%I The hour as a decimal number using a 12-hour clock
(range 01 to 12).
%j The day of the year as a decimal number (range 001
to 366).
%m The month as a decimal number (range 01 to 12).
%M The minute as a decimal number.
%p Either `am' or `pm' according to the given time
value, or the corresponding strings for the current
locale.
%S The second as a decimal number.
%U The week number of the current year as a decimal
number, starting with the first Sunday as the first
day of the first week.
%W The week number of the current year as a decimal
number, starting with the first Monday as the first
day of the first week.
%w The day of the week as a decimal, Sunday being 0.
%x The preferred date representation for the current
locale without the time.
%X The preferred time representation for the current
locale without the date.
%y The year as a decimal number without a century
(range 00 to 99).
%Y The year as a decimal number including the century.
%Z The time zone or name or abbreviation.
%% A literal `%' character.
The broken-down time structure tm is defined in <time.h>
as follows:
struct tm
{
int tm_sec; /* seconds */
int tm_min; /* minutes */
int tm_hour; /* hours */
int tm_mday; /* day of the month */
int tm_mon; /* month */
int tm_year; /* year */
int tm_wday; /* day of the week */
int tm_yday; /* day in the year */
int tm_isdst; /* daylight saving time */
};
The members of the tm structure are:
tm_sec The number of seconds after the minute, normally in
the range 0 to 59, but can be up to 61 to allow for
leap seconds.
tm_min The number of minutes after the hour, in the range
0 to 59.
tm_hour
The number of hours past midnight, in the range 0
to 23.
tm_mday
The day of the month, in the range 1 to 31.
tm_mon The number of months since January, in the range 0
to 11.
tm_year
The number of years since 1900.
tm_wday
The number of days since Sunday, in the range 0 to
6.
tm_yday
The number of days since January 1, in the range 0
to 365.
tm_isdst
A flag that indicates whether daylight saving time
is in effect at the time described. The value is
positive if daylight saving time is in effect, zero
if it is not, and negative if the information is
not available.
RETURN VALUE
The strftime() function returns the number of characters
placed in the array s, not including the terminating NULL
character, provided the string, including the terminating
NULL, fits. Otherwise, it returns 0, and the contents of
the array is undefined. (Thus at least since libc 4.4.4;
very old versions of libc, such as libc 4.4.1, would
return max if the array was too small.)
Note that the return value 0 does not necessarily indicate
an error; for example, in many locales %p yields an empty
string.
CONFORMING TO
ANSI C, SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
date(1) time(2) ctime(3) setlocale(3) sprintf(3)