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.\" $FreeBSD$ 38.\" 39.Dd October 4, 1997 40.Dt STRFTIME 3 41.Os 42.Sh NAME 43.Nm strftime 44.Nd format date and time 45.Sh LIBRARY 46.Lb libc 47.Sh SYNOPSIS 48.In time.h 49.Ft size_t 50.Fn strftime "char *buf" "size_t maxsize" "const char *format" "const struct tm *timeptr" 51.Sh DESCRIPTION 52The 53.Fn strftime 54function formats the information from 55.Fa timeptr 56into the buffer 57.Fa buf 58according to the string pointed to by 59.Fa format . 60.Pp 61The 62.Fa format 63string consists of zero or more conversion specifications and 64ordinary characters. 65All ordinary characters are copied directly into the buffer. 66A conversion specification consists of a percent sign 67.Dq Ql % 68and one other character. 69.Pp 70No more than 71.Fa maxsize 72characters will be placed into the array. 73If the total number of resulting characters, including the terminating 74NUL character, is not more than 75.Fa maxsize , 76.Fn strftime 77returns the number of characters in the array, not counting the 78terminating NUL. 79Otherwise, zero is returned and the buffer contents are indeterminate. 80.Pp 81The conversion specifications are copied to the buffer after expansion 82as follows:- 83.Bl -tag -width "xxxx" 84.It Cm \&%A 85is replaced by national representation of the full weekday name. 86.It Cm %a 87is replaced by national representation of 88the abbreviated weekday name. 89.It Cm \&%B 90is replaced by national representation of the full month name. 91.It Cm %b 92is replaced by national representation of 93the abbreviated month name. 94.It Cm \&%C 95is replaced by (year / 100) as decimal number; single 96digits are preceded by a zero. 97.It Cm %c 98is replaced by national representation of time and date. 99.It Cm \&%D 100is equivalent to 101.Dq Li %m/%d/%y . 102.It Cm %d 103is replaced by the day of the month as a decimal number (01-31). 104.It Cm \&%E* Cm \&%O* 105POSIX locale extensions. 106The sequences 107%Ec %EC %Ex %EX %Ey %EY 108%Od %Oe %OH %OI %Om %OM 109%OS %Ou %OU %OV %Ow %OW %Oy 110are supposed to provide alternate 111representations. 112.Pp 113Additionly %OB implemented 114to represent alternative months names 115(used standalone, without day mentioned). 116.It Cm %e 117is replaced by the day of month as a decimal number (1-31); single 118digits are preceded by a blank. 119.It Cm \&%F 120is equivalent to 121.Dq Li %Y-%m-%d . 122.It Cm \&%G 123is replaced by a year as a decimal number with century. 124This year is the one that contains the greater part of 125the week (Monday as the first day of the week). 126.It Cm %g 127is replaced by the same year as in 128.Dq Li %G , 129but as a decimal number without century (00-99). 130.It Cm \&%H 131is replaced by the hour (24-hour clock) as a decimal number (00-23). 132.It Cm %h 133the same as %b. 134.It Cm \&%I 135is replaced by the hour (12-hour clock) as a decimal number (01-12). 136.It Cm %j 137is replaced by the day of the year as a decimal number (001-366). 138.It Cm %k 139is replaced by the hour (24-hour clock) as a decimal number (0-23); 140single digits are preceded by a blank. 141.It Cm %l 142is replaced by the hour (12-hour clock) as a decimal number (1-12); 143single digits are preceded by a blank. 144.It Cm \&%M 145is replaced by the minute as a decimal number (00-59). 146.It Cm %m 147is replaced by the month as a decimal number (01-12). 148.It Cm %n 149is replaced by a newline. 150.It Cm \&%O* 151the same as %E*. 152.It Cm %p 153is replaced by national representation of either 154"ante meridiem" 155or 156"post meridiem" 157as appropriate. 158.It Cm \&%R 159is equivalent to 160.Dq Li %H:%M . 161.It Cm %r 162is equivalent to 163.Dq Li %I:%M:%S %p . 164.It Cm \&%S 165is replaced by the second as a decimal number (00-60). 166.It Cm %s 167is replaced by the number of seconds since the Epoch, UTC (see 168.Xr mktime 3 ) . 169.It Cm \&%T 170is equivalent to 171.Dq Li %H:%M:%S . 172.It Cm %t 173is replaced by a tab. 174.It Cm \&%U 175is replaced by the week number of the year (Sunday as the first day of 176the week) as a decimal number (00-53). 177.It Cm %u 178is replaced by the weekday (Monday as the first day of the week) 179as a decimal number (1-7). 180.It Cm \&%V 181is replaced by the week number of the year (Monday as the first day of 182the week) as a decimal number (01-53). If the week containing January 1831 has four or more days in the new year, then it is week 1; otherwise 184it is the last week of the previous year, and the next week is week 1. 185.It Cm %v 186is equivalent to 187.Dq Li %e-%b-%Y . 188.It Cm \&%W 189is replaced by the week number of the year (Monday as the first day of 190the week) as a decimal number (00-53). 191.It Cm %w 192is replaced by the weekday (Sunday as the first day of the week) 193as a decimal number (0-6). 194.It Cm \&%X 195is replaced by national representation of the time. 196.It Cm %x 197is replaced by national representation of the date. 198.It Cm \&%Y 199is replaced by the year with century as a decimal number. 200.It Cm %y 201is replaced by the year without century as a decimal number (00-99). 202.It Cm \&%Z 203is replaced by the time zone name. 204.It Cm \&%z 205is replaced by the time zone offset from UTC; a leading plus sign stands for 206east of UTC, a minus sign for west of UTC, hours and minutes follow 207with two digits each and no delimiter between them (common form for 208RFC 822 date headers). 209.It Cm %+ 210is replaced by national representation of the date and time 211(the format is similar to that produced by 212.Xr date 1 ) . 213.It Cm %% 214is replaced by 215.Ql % . 216.El 217.Sh SEE ALSO 218.Xr date 1 , 219.Xr printf 1 , 220.Xr ctime 3 , 221.Xr printf 3 , 222.Xr strptime 3 223.Sh STANDARDS 224The 225.Fn strftime 226function 227conforms to 228.St -isoC 229with a lot of extensions including 230.Ql %C , 231.Ql \&%D , 232.Ql %E* , 233.Ql %e , 234.Ql %G , 235.Ql %g , 236.Ql %h , 237.Ql %k , 238.Ql %l , 239.Ql %n , 240.Ql %O* , 241.Ql \&%R , 242.Ql %r , 243.Ql %s , 244.Ql \&%T , 245.Ql %t , 246.Ql %u , 247.Ql \&%V , 248.Ql %z , 249.Ql %+ . 250.Pp 251The peculiar week number and year in the replacements of 252.Ql %G , 253.Ql %g 254and 255.Ql \&%V 256are defined in ISO 8601: 1988. 257.Sh BUGS 258There is no conversion specification for the phase of the moon. 259