1.\" Copyright (c) 1989, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)strftime.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd November 4, 2004 36.Dt STRFTIME 3 37.Os 38.Sh NAME 39.Nm strftime 40.Nd format date and time 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In time.h 45.Ft size_t 46.Fo strftime 47.Fa "char * restrict buf" 48.Fa "size_t maxsize" 49.Fa "const char * restrict format" 50.Fa "const struct tm * restrict timeptr" 51.Fc 52.Sh DESCRIPTION 53The 54.Fn strftime 55function formats the information from 56.Fa timeptr 57into the buffer 58.Fa buf 59according to the string pointed to by 60.Fa format . 61.Pp 62The 63.Fa format 64string consists of zero or more conversion specifications and 65ordinary characters. 66All ordinary characters are copied directly into the buffer. 67A conversion specification consists of a percent sign 68.Dq Ql % 69and one other character. 70.Pp 71No more than 72.Fa maxsize 73characters will be placed into the array. 74If the total number of resulting characters, including the terminating 75NUL character, is not more than 76.Fa maxsize , 77.Fn strftime 78returns the number of characters in the array, not counting the 79terminating NUL. 80Otherwise, zero is returned and the buffer contents are indeterminate. 81.Pp 82The conversion specifications are copied to the buffer after expansion 83as follows:- 84.Bl -tag -width "xxxx" 85.It Cm \&%A 86is replaced by national representation of the full weekday name. 87.It Cm %a 88is replaced by national representation of 89the abbreviated weekday name. 90.It Cm \&%B 91is replaced by national representation of the full month name. 92.It Cm %b 93is replaced by national representation of 94the abbreviated month name. 95.It Cm \&%C 96is replaced by (year / 100) as decimal number; single 97digits are preceded by a zero. 98.It Cm %c 99is replaced by national representation of time and date. 100.It Cm \&%D 101is equivalent to 102.Dq Li %m/%d/%y . 103.It Cm %d 104is replaced by the day of the month as a decimal number (01-31). 105.It Cm %E* %O* 106POSIX locale extensions. 107The sequences 108%Ec %EC %Ex %EX %Ey %EY 109%Od %Oe %OH %OI %Om %OM 110%OS %Ou %OU %OV %Ow %OW %Oy 111are supposed to provide alternate 112representations. 113.Pp 114Additionally %OB implemented 115to represent alternative months names 116(used standalone, without day mentioned). 117.It Cm %e 118is replaced by the day of the month as a decimal number (1-31); single 119digits are preceded by a blank. 120.It Cm \&%F 121is equivalent to 122.Dq Li %Y-%m-%d . 123.It Cm \&%G 124is replaced by a year as a decimal number with century. 125This year is the one that contains the greater part of 126the week (Monday as the first day of the week). 127.It Cm %g 128is replaced by the same year as in 129.Dq Li %G , 130but as a decimal number without century (00-99). 131.It Cm \&%H 132is replaced by the hour (24-hour clock) as a decimal number (00-23). 133.It Cm %h 134the same as 135.Cm %b . 136.It Cm \&%I 137is replaced by the hour (12-hour clock) as a decimal number (01-12). 138.It Cm %j 139is replaced by the day of the year as a decimal number (001-366). 140.It Cm %k 141is replaced by the hour (24-hour clock) as a decimal number (0-23); 142single digits are preceded by a blank. 143.It Cm %l 144is replaced by the hour (12-hour clock) as a decimal number (1-12); 145single digits are preceded by a blank. 146.It Cm \&%M 147is replaced by the minute as a decimal number (00-59). 148.It Cm %m 149is replaced by the month as a decimal number (01-12). 150.It Cm %n 151is replaced by a newline. 152.It Cm %O* 153the same as 154.Cm %E* . 155.It Cm %p 156is replaced by national representation of either 157"ante meridiem" 158or 159"post meridiem" 160as appropriate. 161.It Cm \&%R 162is equivalent to 163.Dq Li %H:%M . 164.It Cm %r 165is equivalent to 166.Dq Li %I:%M:%S %p . 167.It Cm \&%S 168is replaced by the second as a decimal number (00-60). 169.It Cm %s 170is replaced by the number of seconds since the Epoch, UTC (see 171.Xr mktime 3 ) . 172.It Cm \&%T 173is equivalent to 174.Dq Li %H:%M:%S . 175.It Cm %t 176is replaced by a tab. 177.It Cm \&%U 178is replaced by the week number of the year (Sunday as the first day of 179the week) as a decimal number (00-53). 180.It Cm %u 181is replaced by the weekday (Monday as the first day of the week) 182as a decimal number (1-7). 183.It Cm \&%V 184is replaced by the week number of the year (Monday as the first day of 185the week) as a decimal number (01-53). 186If the week containing January 1871 has four or more days in the new year, then it is week 1; otherwise 188it is the last week of the previous year, and the next week is week 1. 189.It Cm %v 190is equivalent to 191.Dq Li %e-%b-%Y . 192.It Cm \&%W 193is replaced by the week number of the year (Monday as the first day of 194the week) as a decimal number (00-53). 195.It Cm %w 196is replaced by the weekday (Sunday as the first day of the week) 197as a decimal number (0-6). 198.It Cm \&%X 199is replaced by national representation of the time. 200.It Cm %x 201is replaced by national representation of the date. 202.It Cm \&%Y 203is replaced by the year with century as a decimal number. 204.It Cm %y 205is replaced by the year without century as a decimal number (00-99). 206.It Cm \&%Z 207is replaced by the time zone name. 208.It Cm %z 209is replaced by the time zone offset from UTC; a leading plus sign stands for 210east of UTC, a minus sign for west of UTC, hours and minutes follow 211with two digits each and no delimiter between them (common form for 212RFC 822 date headers). 213.It Cm %+ 214is replaced by national representation of the date and time 215(the format is similar to that produced by 216.Xr date 1 ) . 217.It Cm %-* 218GNU libc extension. 219Do not do any padding when performing numerical outputs. 220.It Cm %_* 221GNU libc extension. 222Explicitly specify space for padding. 223.It Cm %0* 224GNU libc extension. 225Explicitly specify zero for padding. 226.It Cm %% 227is replaced by 228.Ql % . 229.El 230.Sh SEE ALSO 231.Xr date 1 , 232.Xr printf 1 , 233.Xr ctime 3 , 234.Xr printf 3 , 235.Xr strptime 3 , 236.Xr wcsftime 3 237.Sh STANDARDS 238The 239.Fn strftime 240function 241conforms to 242.St -isoC 243with a lot of extensions including 244.Ql %C , 245.Ql \&%D , 246.Ql %E* , 247.Ql %e , 248.Ql %G , 249.Ql %g , 250.Ql %h , 251.Ql %k , 252.Ql %l , 253.Ql %n , 254.Ql %O* , 255.Ql \&%R , 256.Ql %r , 257.Ql %s , 258.Ql \&%T , 259.Ql %t , 260.Ql %u , 261.Ql \&%V , 262.Ql %z , 263.Ql %+ . 264.Pp 265The peculiar week number and year in the replacements of 266.Ql %G , 267.Ql %g 268and 269.Ql \&%V 270are defined in ISO 8601: 1988. 271.Sh BUGS 272There is no conversion specification for the phase of the moon. 273.Pp 274The 275.Fn strftime 276function does not correctly handle multibyte characters in the 277.Fa format 278argument. 279