strftime,
strftime_l — format date and
time
Standard C Library (libc, -lc)
#include
<time.h>
size_t
strftime(char *restrict s,
size_t maxsize, const char *restrict
format, const struct tm *restrict timeptr);
#include <time.h>
#include <xlocale.h>
size_t
strftime_l(char *restrict s,
size_t maxsize, const char *restrict
format, const struct tm *restrict timeptr,
locale_t loc);
The
strftime()
function formats the information from timeptr into the
buffer s, according to the string pointed to by
format.
The format string consists of zero or more
conversion specifications and ordinary characters. All ordinary characters
are copied directly into the buffer. A conversion specification consists of
a percent sign “‘%’” and
one other character.
No more than maxsize
characters will be placed into the array. If the total number of resulting
characters, including the terminating NUL character, is not more than
maxsize,
strftime()
returns the number of characters in the array, not counting the terminating
NUL. Otherwise, zero is returned and the buffer contents are
indeterminate.
Although the
strftime()
function uses the current locale, the
strftime_l()
function may be passed a locale directly. See
xlocale(3) for more information.
The conversion specifications are copied to the buffer after
expansion as follows:-
%A- is replaced by national representation of the full weekday name.
%a- is replaced by national representation of the abbreviated weekday
name.
%B- is replaced by national representation of the full month name.
%b- is replaced by national representation of the abbreviated month name.
%C- is replaced by (year / 100) as decimal number; single digits are preceded
by a zero.
%c- is replaced by national representation of time and date.
%D- is equivalent to “
%m/%d/%y”.
%d- is replaced by the day of the month as a decimal number (01-31).
%E*
%O*- POSIX locale extensions. The sequences %Ec %EC %Ex %EX %Ey %EY %Od %Oe %OH
%OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy are supposed to provide alternate
representations.
Additionally %OB implemented to represent alternative months
names (used standalone, without day mentioned).
%e- is replaced by the day of the month as a decimal number (1-31); single
digits are preceded by a blank.
%F- is equivalent to “
%Y-%m-%d”.
%G- is replaced by a year as a decimal number with century. This year is the
one that contains the greater part of the week (Monday as the first day of
the week).
%g- is replaced by the same year as in
“
%G”, but as a decimal number
without century (00-99).
%H- is replaced by the hour (24-hour clock) as a decimal number (00-23).
%h- the same as
%b.
%I- is replaced by the hour (12-hour clock) as a decimal number (01-12).
%j- is replaced by the day of the year as a decimal number (001-366).
%k- is replaced by the hour (24-hour clock) as a decimal number (0-23); single
digits are preceded by a blank.
%l- is replaced by the hour (12-hour clock) as a decimal number (1-12); single
digits are preceded by a blank.
%M- is replaced by the minute as a decimal number (00-59).
%m- is replaced by the month as a decimal number (01-12).
%n- is replaced by a newline.
%O*- the same as
%E*.
%p- is replaced by national representation of either "ante meridiem"
(a.m.) or "post meridiem" (p.m.) as appropriate.
%R- is equivalent to “
%H:%M”.
%r- is equivalent to “
%I:%M:%S %p”.
%S- is replaced by the second as a decimal number (00-60).
%s- is replaced by the number of seconds since the Epoch, UTC (see
mktime(3)).
%T- is equivalent to “
%H:%M:%S”.
%t- is replaced by a tab.
%U- is replaced by the week number of the year (Sunday as the first day of the
week) as a decimal number (00-53).
%u- is replaced by the weekday (Monday as the first day of the week) as a
decimal number (1-7).
%V- is replaced by the week number of the year (Monday as the first day of the
week) as a decimal number (01-53). If the week containing January 1 has
four or more days in the new year, then it is week 1; otherwise it is the
last week of the previous year, and the next week is week 1.
%v- is equivalent to “
%e-%b-%Y”.
%W- is replaced by the week number of the year (Monday as the first day of the
week) as a decimal number (00-53).
%w- is replaced by the weekday (Sunday as the first day of the week) as a
decimal number (0-6).
%X- is replaced by national representation of the time.
%x- is replaced by national representation of the date.
%Y- is replaced by the year with century as a decimal number.
%y- is replaced by the year without century as a decimal number (00-99).
%Z- is replaced by the time zone name.
%z- is replaced by the time zone offset from UTC; a leading plus sign stands
for east of UTC, a minus sign for west of UTC, hours and minutes follow
with two digits each and no delimiter between them (common form for RFC
822 date headers).
%+- is replaced by national representation of the date and time (the format is
similar to that produced by
date(1)).
%-*- GNU libc extension. Do not do any padding when performing numerical
outputs.
%_*- GNU libc extension. Explicitly specify space for padding.
%0*- GNU libc extension. Explicitly specify zero for padding.
%%- is replaced by ‘
%’.
The strftime() function conforms to
ISO/IEC 9899:1990 (“ISO C90”)
with a lot of extensions including
‘%C’,
‘%D’,
‘%E*’,
‘%e’,
‘%G’,
‘%g’,
‘%h’,
‘%k’,
‘%l’,
‘%n’,
‘%O*’,
‘%R’,
‘%r’,
‘%s’,
‘%T’,
‘%t’,
‘%u’,
‘%V’,
‘%z’, and
‘%+’.
The peculiar week number and year in the replacements of
‘%G’,
‘%g’, and
‘%V’ are defined in ISO 8601:
1988.
There is no conversion specification for the phase of the
moon.
The strftime() function does not correctly
handle multibyte characters in the format
argument.