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 January 4, 2003 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.Fo strftime 51.Fa "char * restrict buf" 52.Fa "size_t maxsize" 53.Fa "const char * restrict format" 54.Fa "const struct tm * restrict timeptr" 55.Fc 56.Sh DESCRIPTION 57The 58.Fn strftime 59function formats the information from 60.Fa timeptr 61into the buffer 62.Fa buf 63according to the string pointed to by 64.Fa format . 65.Pp 66The 67.Fa format 68string consists of zero or more conversion specifications and 69ordinary characters. 70All ordinary characters are copied directly into the buffer. 71A conversion specification consists of a percent sign 72.Dq Ql % 73and one other character. 74.Pp 75No more than 76.Fa maxsize 77characters will be placed into the array. 78If the total number of resulting characters, including the terminating 79NUL character, is not more than 80.Fa maxsize , 81.Fn strftime 82returns the number of characters in the array, not counting the 83terminating NUL. 84Otherwise, zero is returned and the buffer contents are indeterminate. 85.Pp 86The conversion specifications are copied to the buffer after expansion 87as follows:- 88.Bl -tag -width "xxxx" 89.It Cm \&%A 90is replaced by national representation of the full weekday name. 91.It Cm %a 92is replaced by national representation of 93the abbreviated weekday name. 94.It Cm \&%B 95is replaced by national representation of the full month name. 96.It Cm %b 97is replaced by national representation of 98the abbreviated month name. 99.It Cm \&%C 100is replaced by (year / 100) as decimal number; single 101digits are preceded by a zero. 102.It Cm %c 103is replaced by national representation of time and date. 104.It Cm \&%D 105is equivalent to 106.Dq Li %m/%d/%y . 107.It Cm %d 108is replaced by the day of the month as a decimal number (01-31). 109.It Cm \&%E* Cm \&%O* 110POSIX locale extensions. 111The sequences 112%Ec %EC %Ex %EX %Ey %EY 113%Od %Oe %OH %OI %Om %OM 114%OS %Ou %OU %OV %Ow %OW %Oy 115are supposed to provide alternate 116representations. 117.Pp 118Additionly %OB implemented 119to represent alternative months names 120(used standalone, without day mentioned). 121.It Cm %e 122is replaced by the day of month as a decimal number (1-31); single 123digits are preceded by a blank. 124.It Cm \&%F 125is equivalent to 126.Dq Li %Y-%m-%d . 127.It Cm \&%G 128is replaced by a year as a decimal number with century. 129This year is the one that contains the greater part of 130the week (Monday as the first day of the week). 131.It Cm %g 132is replaced by the same year as in 133.Dq Li %G , 134but as a decimal number without century (00-99). 135.It Cm \&%H 136is replaced by the hour (24-hour clock) as a decimal number (00-23). 137.It Cm %h 138the same as %b. 139.It Cm \&%I 140is replaced by the hour (12-hour clock) as a decimal number (01-12). 141.It Cm %j 142is replaced by the day of the year as a decimal number (001-366). 143.It Cm %k 144is replaced by the hour (24-hour clock) as a decimal number (0-23); 145single digits are preceded by a blank. 146.It Cm %l 147is replaced by the hour (12-hour clock) as a decimal number (1-12); 148single digits are preceded by a blank. 149.It Cm \&%M 150is replaced by the minute as a decimal number (00-59). 151.It Cm %m 152is replaced by the month as a decimal number (01-12). 153.It Cm %n 154is replaced by a newline. 155.It Cm \&%O* 156the same as %E*. 157.It Cm %p 158is replaced by national representation of either 159"ante meridiem" 160or 161"post meridiem" 162as appropriate. 163.It Cm \&%R 164is equivalent to 165.Dq Li %H:%M . 166.It Cm %r 167is equivalent to 168.Dq Li %I:%M:%S %p . 169.It Cm \&%S 170is replaced by the second as a decimal number (00-60). 171.It Cm %s 172is replaced by the number of seconds since the Epoch, UTC (see 173.Xr mktime 3 ) . 174.It Cm \&%T 175is equivalent to 176.Dq Li %H:%M:%S . 177.It Cm %t 178is replaced by a tab. 179.It Cm \&%U 180is replaced by the week number of the year (Sunday as the first day of 181the week) as a decimal number (00-53). 182.It Cm %u 183is replaced by the weekday (Monday as the first day of the week) 184as a decimal number (1-7). 185.It Cm \&%V 186is replaced by the week number of the year (Monday as the first day of 187the week) as a decimal number (01-53). 188If 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.Xr wcsftime 3 230.Sh STANDARDS 231The 232.Fn strftime 233function 234conforms to 235.St -isoC 236with a lot of extensions including 237.Ql %C , 238.Ql \&%D , 239.Ql %E* , 240.Ql %e , 241.Ql %G , 242.Ql %g , 243.Ql %h , 244.Ql %k , 245.Ql %l , 246.Ql %n , 247.Ql %O* , 248.Ql \&%R , 249.Ql %r , 250.Ql %s , 251.Ql \&%T , 252.Ql %t , 253.Ql %u , 254.Ql \&%V , 255.Ql %z , 256.Ql %+ . 257.Pp 258The peculiar week number and year in the replacements of 259.Ql %G , 260.Ql %g 261and 262.Ql \&%V 263are defined in ISO 8601: 1988. 264.Sh BUGS 265There is no conversion specification for the phase of the moon. 266.Pp 267The 268.Fn strftime 269function does not correctly handle multibyte characters in the 270.Fa format 271argument. 272