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IABSD.fr/src/lib/libc/time/strftime.3
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.\" $OpenBSD: strftime.3,v 1.38 2019/05/16 13:35:17 schwarze Exp $ .\" .\" Copyright (c) 1989, 1991 The Regents of the University of California. .\" All rights reserved. .\" .\" This code is derived from software contributed to Berkeley by .\" the American National Standards Committee X3, on Information .\" Processing Systems. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" from: @(#)strftime.3 5.12 (Berkeley) 6/29/91 .\" .Dd $Mdocdate: May 16 2019 $ .Dt STRFTIME 3 .Os .Sh NAME .Nm strftime , .Nm strftime_l .Nd format date and time .Sh SYNOPSIS .In time.h .Ft size_t .Fo strftime .Fa "char *buf" .Fa "size_t maxsize" .Fa "const char *format" .Fa "const struct tm *timeptr" .Fc .Ft size_t .Fo strftime_l .Fa "char *buf" .Fa "size_t maxsize" .Fa "const char *format" .Fa "const struct tm *timeptr" .Fa "locale_t locale" .Fc .Sh DESCRIPTION These functions format the information from .Fa timeptr (as described in .Xr mktime 3 ) into the buffer .Fa buf according to the string pointed to by .Fa format . .Pp The .Fa 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 .Ql % and one other character. .Pp No more than .Fa maxsize characters will be placed into the array. .Pp Each conversion specification is replaced by the characters as follows which are then copied into the buffer. .Bl -tag -width "xxxx" .It Cm \&%A is replaced by the locale's full weekday name. .It Cm \&%a is replaced by the locale's abbreviated weekday name. .It Cm \&%B is replaced by the locale's full month name. .It Cm \&%b No or Cm \&%h is replaced by the locale's abbreviated month name. .It Cm \&%C is replaced by the century (a year divided by 100 and truncated to an integer) as a decimal number (00\-99). .It Cm \&%c is replaced by the locale's appropriate date and time representation. .It Cm \&%D is replaced by the date in the format .Dq Li %m/%d/%y . .It Cm \&%d is replaced by the day of the month as a decimal number (01\-31). .It Cm \&%e is replaced by the day of month as a decimal number (1\-31); single digits are preceded by a blank. .It Cm \&%F is replaced by the date in the format .Dq Li %Y-%m-%d . .It Cm \&%G is replaced by the .St -iso8601 year with century as a decimal number. .It Cm \&%g is replaced by the .St -iso8601 year without century as a decimal number (00\-99). .It Cm \&%H is replaced by the hour (24-hour clock) as a decimal number (00\-23). .It Cm \&%I is replaced by the hour (12-hour clock) as a decimal number (01\-12). .It Cm \&%j is replaced by the day of the year as a decimal number (001\-366). .It Cm \&%k is replaced by the hour (24-hour clock) as a decimal number (0\-23); single digits are preceded by a blank. .It Cm \&%l is replaced by the hour (12-hour clock) as a decimal number (1\-12); single digits are preceded by a blank. .It Cm \&%M is replaced by the minute as a decimal number (00\-59). .It Cm %m is replaced by the month as a decimal number (01\-12). .It Cm %n is replaced by a newline. .It Cm %p is replaced by the locale's equivalent of either .Dq AM or .Dq PM . .It Cm \&%R is replaced by the time in the format .Dq Li %H:%M . .It Cm \&%r is replaced by the locale's representation of 12-hour clock time using AM/PM notation. .It Cm \&%S is replaced by the second as a decimal number (00\-60). The range of seconds is (00\-60) instead of (00\-59) to allow for the periodic occurrence of leap seconds. .It Cm %s is replaced by the number of seconds since the Epoch, UTC (see .Xr mktime 3 ) . .It Cm \&%T is replaced by the time in the format .Dq Li %H:%M:%S . .It Cm \&%t is replaced by a tab. .It Cm \&%U is replaced by the week number of the year (Sunday as the first day of the week) as a decimal number (00\-53). .It Cm \&%u is replaced by the weekday (Monday as the first day of the week) as a decimal number (1\-7). .It Cm \&%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 week 53 of the previous year, and the next week is week 1. .It Cm \&%v is replaced by the date in the format .Dq Li "%e-%b-%Y" . .It Cm \&%W is replaced by the week number of the year (Monday as the first day of the week) as a decimal number (00\-53). .It Cm \&%w is replaced by the weekday (Sunday as the first day of the week) as a decimal number (0\-6). .It Cm \&%X is replaced by the locale's appropriate time representation. .It Cm \&%x is replaced by the locale's appropriate date representation. .It Cm \&%Y is replaced by the year with century as a decimal number. .It Cm \&%y is replaced by the year without century as a decimal number (00\-99). .It Cm \&%Z is replaced by the time zone name, or by the empty string if this is not determinable. .It Cm \&%z is replaced by the offset from UTC in the format .Dq Li +HHMM or .Dq Li -HHMM as appropriate, with positive values representing locations east of Greenwich, or by the empty string if this is not determinable. .It Cm %% is replaced by .Ql % . .It Cm %+ is replaced by the date and time in .Xr date 1 format. .El .Pp The .Ox implementation always uses the C locale and ignores the global locale, the thread-specific locale, and the .Fa locale argument. .Sh RETURN VALUES If the total number of resulting characters, including the terminating NUL character, is not more than .Fa maxsize , .Fn strftime returns the number of characters placed in the array, not counting the terminating NUL. Otherwise, zero is returned. .Sh SEE ALSO .Xr date 1 , .Xr printf 1 , .Xr ctime 3 , .Xr getenv 3 , .Xr printf 3 , .Xr strptime 3 , .Xr time 3 , .Xr tzset 3 , .Xr tzfile 5 .Sh STANDARDS The .Fn strftime function conforms to .St -isoC-99 , and .Fn strftime_l to .St -p1003.1-2008 , except that the .Ql E and .Ql O conversion modifiers are ignored by this implementation. .Pp The .Ql \&%k , .Ql \&%l , .Ql \&%s , .Ql \&%v , and .Ql \&%+ conversion specifications are extensions. .Pp Use of the .St -iso8601 conversions may produce non-intuitive results. Week 01 of a year is per definition the first week which has the Thursday in this year, which is equivalent to the week which contains the fourth day of January. In other words, the first week of a new year is the week which has the majority of its days in the new year. Week 01 might also contain days from the previous year and the week before week 01 of a year is the last week (52 or 53) of the previous year even if it contains days from the new year. A week starts with Monday (day 1) and ends with Sunday (day 7). For example, the first week of the year 1997 lasts from 1996-12-30 to 1997-01-05. .Sh HISTORY A predecessor to .Fn strftime , .Fn ptime , first appeared in .At v1 . The .Fn strftime function has been available since .Bx 4.3 Reno , and .Fn strftime_l since .Ox 6.2 . .Sh AUTHORS .An Keith Bostic implemented the .Bx version of .Fn strftime in 1989. .Sh CAVEATS On systems other than .Ox , the .Dv LC_TIME .Xr locale 1 category can cause erratic output; see CAVEATS in .Xr setlocale 3 for details. .Sh BUGS There is no conversion specification for the phase of the moon. .Pp Note that while this implementation of .Fn strftime will always NUL terminate .Fa buf , other implementations may not do so when .Fa maxsize is not large enough to store the entire time string. The contents of .Fa buf are implementation specific in this case.