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.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)strftime.3 8.1 (Berkeley) 6/4/93 37.\" $FreeBSD: src/lib/libc/stdtime/strftime.3,v 1.18.2.10 2003/05/24 00:01:31 keramida Exp $ 38.\" $DragonFly: src/lib/libc/stdtime/strftime.3,v 1.3 2007/05/17 08:19:00 swildner Exp $ 39.\" 40.Dd January 4, 2003 41.Dt STRFTIME 3 42.Os 43.Sh NAME 44.Nm strftime 45.Nd format date and time 46.Sh LIBRARY 47.Lb libc 48.Sh SYNOPSIS 49.In time.h 50.Ft size_t 51.Fo strftime 52.Fa "char * restrict buf" 53.Fa "size_t maxsize" 54.Fa "const char * restrict format" 55.Fa "const struct tm * restrict timeptr" 56.Fc 57.Sh DESCRIPTION 58The 59.Fn strftime 60function formats the information from 61.Fa timeptr 62into the buffer 63.Fa buf 64according to the string pointed to by 65.Fa format . 66.Pp 67The 68.Fa format 69string consists of zero or more conversion specifications and 70ordinary characters. 71All ordinary characters are copied directly into the buffer. 72A conversion specification consists of a percent sign 73.Dq Ql % 74and one other character. 75.Pp 76No more than 77.Fa maxsize 78characters will be placed into the array. 79If the total number of resulting characters, including the terminating 80NUL character, is not more than 81.Fa maxsize , 82.Fn strftime 83returns the number of characters in the array, not counting the 84terminating NUL. 85Otherwise, zero is returned and the buffer contents are indeterminate. 86.Pp 87The conversion specifications are copied to the buffer after expansion 88as follows:- 89.Bl -tag -width "xxxx" 90.It Cm \&%A 91is replaced by national representation of the full weekday name. 92.It Cm %a 93is replaced by national representation of 94the abbreviated weekday name. 95.It Cm \&%B 96is replaced by national representation of the full month name. 97.It Cm %b 98is replaced by national representation of 99the abbreviated month name. 100.It Cm \&%C 101is replaced by (year / 100) as decimal number; single 102digits are preceded by a zero. 103.It Cm %c 104is replaced by national representation of time and date. 105.It Cm \&%D 106is equivalent to 107.Dq Li %m/%d/%y . 108.It Cm %d 109is replaced by the day of the month as a decimal number (01-31). 110.It Cm \&%E* Cm \&%O* 111POSIX locale extensions. 112The sequences 113%Ec %EC %Ex %EX %Ey %EY 114%Od %Oe %OH %OI %Om %OM 115%OS %Ou %OU %OV %Ow %OW %Oy 116are supposed to provide alternate 117representations. 118.Pp 119Additionally %OB implemented 120to represent alternative months names 121(used standalone, without day mentioned). 122.It Cm %e 123is replaced by the day of month as a decimal number (1-31); single 124digits are preceded by a blank. 125.It Cm \&%F 126is equivalent to 127.Dq Li %Y-%m-%d . 128.It Cm \&%G 129is replaced by a year as a decimal number with century. 130This year is the one that contains the greater part of 131the week (Monday as the first day of the week). 132.It Cm %g 133is replaced by the same year as in 134.Dq Li %G , 135but as a decimal number without century (00-99). 136.It Cm \&%H 137is replaced by the hour (24-hour clock) as a decimal number (00-23). 138.It Cm %h 139the same as %b. 140.It Cm \&%I 141is replaced by the hour (12-hour clock) as a decimal number (01-12). 142.It Cm %j 143is replaced by the day of the year as a decimal number (001-366). 144.It Cm %k 145is replaced by the hour (24-hour clock) as a decimal number (0-23); 146single digits are preceded by a blank. 147.It Cm %l 148is replaced by the hour (12-hour clock) as a decimal number (1-12); 149single digits are preceded by a blank. 150.It Cm \&%M 151is replaced by the minute as a decimal number (00-59). 152.It Cm %m 153is replaced by the month as a decimal number (01-12). 154.It Cm %n 155is replaced by a newline. 156.It Cm \&%O* 157the same as %E*. 158.It Cm %p 159is replaced by national representation of either 160"ante meridiem" 161or 162"post meridiem" 163as appropriate. 164.It Cm \&%R 165is equivalent to 166.Dq Li %H:%M . 167.It Cm %r 168is equivalent to 169.Dq Li %I:%M:%S %p . 170.It Cm \&%S 171is replaced by the second as a decimal number (00-60). 172.It Cm %s 173is replaced by the number of seconds since the Epoch, UTC (see 174.Xr mktime 3 ) . 175.It Cm \&%T 176is equivalent to 177.Dq Li %H:%M:%S . 178.It Cm %t 179is replaced by a tab. 180.It Cm \&%U 181is replaced by the week number of the year (Sunday as the first day of 182the week) as a decimal number (00-53). 183.It Cm %u 184is replaced by the weekday (Monday as the first day of the week) 185as a decimal number (1-7). 186.It Cm \&%V 187is replaced by the week number of the year (Monday as the first day of 188the week) as a decimal number (01-53). If the week containing January 1891 has four or more days in the new year, then it is week 1; otherwise 190it is the last week of the previous year, and the next week is week 1. 191.It Cm %v 192is equivalent to 193.Dq Li %e-%b-%Y . 194.It Cm \&%W 195is replaced by the week number of the year (Monday as the first day of 196the week) as a decimal number (00-53). 197.It Cm %w 198is replaced by the weekday (Sunday as the first day of the week) 199as a decimal number (0-6). 200.It Cm \&%X 201is replaced by national representation of the time. 202.It Cm %x 203is replaced by national representation of the date. 204.It Cm \&%Y 205is replaced by the year with century as a decimal number. 206.It Cm %y 207is replaced by the year without century as a decimal number (00-99). 208.It Cm \&%Z 209is replaced by the time zone name. 210.It Cm \&%z 211is replaced by the time zone offset from UTC; a leading plus sign stands for 212east of UTC, a minus sign for west of UTC, hours and minutes follow 213with two digits each and no delimiter between them (common form for 214RFC 822 date headers). 215.It Cm %+ 216is replaced by national representation of the date and time 217(the format is similar to that produced by 218.Xr date 1 ) . 219.It Cm %% 220is replaced by 221.Ql % . 222.El 223.Sh SEE ALSO 224.Xr date 1 , 225.Xr printf 1 , 226.Xr ctime 3 , 227.Xr printf 3 , 228.Xr strptime 3 229.Sh STANDARDS 230The 231.Fn strftime 232function 233conforms to 234.St -isoC 235with a lot of extensions including 236.Ql %C , 237.Ql \&%D , 238.Ql %E* , 239.Ql %e , 240.Ql %G , 241.Ql %g , 242.Ql %h , 243.Ql %k , 244.Ql %l , 245.Ql %n , 246.Ql %O* , 247.Ql \&%R , 248.Ql %r , 249.Ql %s , 250.Ql \&%T , 251.Ql %t , 252.Ql %u , 253.Ql \&%V , 254.Ql %z , 255.Ql %+ . 256.Pp 257The peculiar week number and year in the replacements of 258.Ql %G , 259.Ql %g 260and 261.Ql \&%V 262are defined in ISO 8601: 1988. 263.Sh BUGS 264There is no conversion specification for the phase of the moon. 265