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.\" $FreeBSD: src/lib/libc/stdtime/strftime.3,v 1.18.2.10 2003/05/24 00:01:31 keramida Exp $ 37.\" 38.Dd October 19, 2008 39.Dt STRFTIME 3 40.Os 41.Sh NAME 42.Nm strftime 43.Nd format date and time 44.Sh LIBRARY 45.Lb libc 46.Sh SYNOPSIS 47.In time.h 48.Ft size_t 49.Fo strftime 50.Fa "char * restrict buf" 51.Fa "size_t maxsize" 52.Fa "const char * restrict format" 53.Fa "const struct tm * restrict timeptr" 54.Fc 55.Sh DESCRIPTION 56The 57.Fn strftime 58function formats the information from 59.Fa timeptr 60into the buffer 61.Fa buf 62according to the string pointed to by 63.Fa format . 64.Pp 65The 66.Fa format 67string consists of zero or more conversion specifications and 68ordinary characters. 69All ordinary characters are copied directly into the buffer. 70A conversion specification consists of a percent sign 71.Dq Ql % 72and one other character. 73.Pp 74No more than 75.Fa maxsize 76characters will be placed into the array. 77If the total number of resulting characters, including the terminating 78NUL character, is not more than 79.Fa maxsize , 80.Fn strftime 81returns the number of characters in the array, not counting the 82terminating NUL. 83Otherwise, zero is returned and the buffer contents are indeterminate. 84.Pp 85The conversion specifications are copied to the buffer after expansion 86as follows:- 87.Bl -tag -width "xxxx" 88.It Cm \&%A 89is replaced by national representation of the full weekday name. 90.It Cm %a 91is replaced by national representation of 92the abbreviated weekday name. 93.It Cm \&%B 94is replaced by national representation of the full month name. 95.It Cm %b 96is replaced by national representation of 97the abbreviated month name. 98.It Cm \&%C 99is replaced by (year / 100) as decimal number; single 100digits are preceded by a zero. 101.It Cm %c 102is replaced by national representation of time and date. 103.It Cm \&%D 104is equivalent to 105.Dq Li %m/%d/%y . 106.It Cm %d 107is replaced by the day of the month as a decimal number (01-31). 108.It Cm \&%E* Cm \&%O* 109POSIX locale extensions. 110The sequences 111%Ec %EC %Ex %EX %Ey %EY 112%Od %Oe %OH %OI %Om %OM 113%OS %Ou %OU %OV %Ow %OW %Oy 114are supposed to provide alternate 115representations. 116.Pp 117Additionally %OB implemented 118to represent alternative months names 119(used standalone, without day mentioned). 120.It Cm %e 121is replaced by the day of month as a decimal number (1-31); single 122digits are preceded by a blank. 123.It Cm \&%F 124is replaced by the date in the format 125.Dq Li %Y-%m-%d . 126.It Cm \&%G 127is replaced by a year as a decimal number with century. 128This year is the one that contains the greater part of 129the week (Monday as the first day of the week). 130.It Cm %g 131is replaced by the same year as in 132.Dq Li %G , 133but as a decimal number without century (00-99). 134.It Cm \&%H 135is replaced by the hour (24-hour clock) as a decimal number (00-23). 136.It Cm %h 137the same as %b. 138.It Cm \&%I 139is replaced by the hour (12-hour clock) as a decimal number (01-12). 140.It Cm %j 141is replaced by the day of the year as a decimal number (001-366). 142.It Cm %k 143is replaced by the hour (24-hour clock) as a decimal number (0-23); 144single digits are preceded by a blank. 145.It Cm %l 146is replaced by the hour (12-hour clock) as a decimal number (1-12); 147single digits are preceded by a blank. 148.It Cm \&%M 149is replaced by the minute as a decimal number (00-59). 150.It Cm %m 151is replaced by the month as a decimal number (01-12). 152.It Cm %n 153is replaced by a newline. 154.It Cm \&%O* 155the same as %E*. 156.It Cm %p 157is replaced by national representation of either 158"ante meridiem" 159or 160"post meridiem" 161as appropriate. 162.It Cm \&%R 163is equivalent to 164.Dq Li %H:%M . 165.It Cm %r 166is equivalent to 167.Dq Li %I:%M:%S %p . 168.It Cm \&%S 169is replaced by the second as a decimal number (00-60). 170.It Cm %s 171is replaced by the number of seconds since the Epoch, UTC (see 172.Xr mktime 3 ) . 173.It Cm \&%T 174is equivalent to 175.Dq Li %H:%M:%S . 176.It Cm %t 177is replaced by a tab. 178.It Cm \&%U 179is replaced by the week number of the year (Sunday as the first day of 180the week) as a decimal number (00-53). 181.It Cm %u 182is replaced by the weekday (Monday as the first day of the week) 183as a decimal number (1-7). 184.It Cm \&%V 185is replaced by the week number of the year (Monday as the first day of 186the week) as a decimal number (01-53). If 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, 208or by the empty string if this is not determinable. 209.It Cm \&%z 210is replaced by the offset from UTC in the format 211.Li ++HHMM 212or 213.Li --HHMM 214as appropriate, 215with positive values representing locations east of Greenwich, 216or by the empty string if this is not determinable. 217.It Cm %+ 218is replaced by national representation of the date and time 219(the format is similar to that produced by 220.Xr date 1 ) . 221.It Cm %% 222is replaced by 223.Ql % . 224.El 225.Sh SEE ALSO 226.Xr date 1 , 227.Xr printf 1 , 228.Xr ctime 3 , 229.Xr printf 3 , 230.Xr strptime 3 231.Sh STANDARDS 232The 233.Fn strftime 234function 235conforms to 236.St -isoC 237with a lot of extensions including 238.Ql %C , 239.Ql \&%D , 240.Ql %E* , 241.Ql %e , 242.Ql %G , 243.Ql %g , 244.Ql %h , 245.Ql %k , 246.Ql %l , 247.Ql %n , 248.Ql %O* , 249.Ql \&%R , 250.Ql %r , 251.Ql %s , 252.Ql \&%T , 253.Ql %t , 254.Ql %u , 255.Ql \&%V , 256.Ql %z , 257.Ql %+ . 258.Pp 259The peculiar week number and year in the replacements of 260.Ql %G , 261.Ql %g 262and 263.Ql \&%V 264are defined in ISO 8601: 1988. 265.Sh BUGS 266There is no conversion specification for the phase of the moon. 267