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.\" 38.Dd October 4, 1997 39.Dt STRFTIME 3 40.Os 41.Sh NAME 42.Nm strftime 43.Nd format date and time 44.Sh SYNOPSIS 45.Fd #include <time.h> 46.Ft size_t 47.Fn strftime "char *buf" "size_t maxsize" "const char *format" "const struct tm *timeptr" 48.Sh DESCRIPTION 49The 50.Fn strftime 51function formats the information from 52.Fa timeptr 53into the buffer 54.Fa buf 55according to the string pointed to by 56.Fa format . 57.Pp 58The 59.Fa format 60string consists of zero or more conversion specifications and 61ordinary characters. 62All ordinary characters are copied directly into the buffer. 63A conversion specification consists of a percent sign 64.Dq Ql % 65and one other character. 66.Pp 67No more than 68.Fa maxsize 69characters will be placed into the array. 70If the total number of resulting characters, including the terminating 71null character, is not more than 72.Fa maxsize , 73.Fn strftime 74returns the number of characters in the array, not counting the 75terminating null. 76Otherwise, zero is returned and the buffer contents is indeterminate. 77.Pp 78Each conversion specification is replaced by the characters as 79follows which are then copied into the buffer. 80.Bl -tag -width "xxxx" 81.It Cm \&%A 82is replaced by national representation of the full weekday name. 83.It Cm %a 84is replaced by national representation of 85the abbreviated weekday name, where the abbreviation 86is the first three characters. 87.It Cm \&%B 88is replaced by national representation of the full month name. 89.It Cm %b 90is replaced by national representation of 91the abbreviated month name, where the abbreviation is 92the first three characters. 93.It Cm \&%C 94is replaced by (year / 100) as decimal number; single 95digits are preceded by a zero. 96.It Cm %c 97is replaced by national representation of time and date 98(the format is similar with produced by 99.Xr asctime 3 ) . 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* 106POSIX locale extensions. 107The sequences 108%Ec %EC %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.It Cm %e 114is replaced by the day of month as a decimal number (1-31); single 115digits are preceded by a blank. 116.It Cm \&%G 117is replaced by a year as a decimal number with century. 118This year is the one that contains the greater part of 119the week (Monday as the first day of the week). 120.It Cm %g 121is replaced by the same year as in 122.Dq Li %G , 123but as a decimal number without century (00-99). 124.It Cm \&%H 125is replaced by the hour (24-hour clock) as a decimal number (00-23). 126.It Cm %h 127the same as %b. 128.It Cm \&%I 129is replaced by the hour (12-hour clock) as a decimal number (01-12). 130.It Cm %j 131is replaced by the day of the year as a decimal number (001-366). 132.It Cm %k 133is replaced by the hour (24-hour clock) as a decimal number (0-23); 134single digits are preceded by a blank. 135.It Cm %l 136is replaced by the hour (12-hour clock) as a decimal number (1-12); 137single digits are preceded by a blank. 138.It Cm \&%M 139is replaced by the minute as a decimal number (00-59). 140.It Cm %m 141is replaced by the month as a decimal number (01-12). 142.It Cm %n 143is replaced by a newline. 144.It Cm \&%O* 145the same as %E*. 146.It Cm %p 147is replaced by national representation of either 148"ante meridiem" 149or 150"post meridiem" 151as appropriate. 152.It Cm \&%R 153is equivalent to 154.Dq Li %H:%M . 155.It Cm %r 156is equivalent to 157.Dq Li %I:%M:%S %p . 158.It Cm \&%S 159is replaced by the second as a decimal number (00-60). 160.It Cm %s 161is replaced by the number of seconds since the Epoch, UTC (see 162.Xr mktime 3 ) . 163.It Cm \&%T 164is equivalent to 165.Dq Li %H:%M:%S . 166.It Cm %t 167is replaced by a tab. 168.It Cm \&%U 169is replaced by the week number of the year (Sunday as the first day of 170the week) as a decimal number (00-53). 171.It Cm %u 172is replaced by the weekday (Monday as the first day of the week) 173as a decimal number (1-7). 174.It Cm \&%V 175is replaced by the week number of the year (Monday as the first day of 176the week) as a decimal number (01-53). If the week containing January 1771 has four or more days in the new year, then it is week 1; otherwise 178it is the last week of the previous year, and the next week is week 1. 179.It Cm %v 180is equivalent to 181.Dq Li %e-%b-%Y . 182.It Cm \&%W 183is replaced by the week number of the year (Monday as the first day of 184the week) as a decimal number (00-53). 185.It Cm %w 186is replaced by the weekday (Sunday as the first day of the week) 187as a decimal number (0-6). 188.It Cm \&%X 189is replaced by national representation of the time. 190.It Cm %x 191is replaced by national representation of the date. 192.It Cm \&%Y 193is replaced by the year with century as a decimal number. 194.It Cm %y 195is replaced by the year without century as a decimal number (00-99). 196.It Cm \&%Z 197is replaced by the time zone name. 198.It Cm %+ 199is replaced by national representation of the date and time 200(the format is similar with produced by 201.Xr date 1 ) . 202.It Cm %% 203is replaced by 204.Ql % . 205.El 206.Sh SEE ALSO 207.Xr date 1 , 208.Xr printf 1 , 209.Xr ctime 3 , 210.Xr printf 3 , 211.Xr strptime 3 212.Sh STANDARDS 213The 214.Fn strftime 215function 216conforms to 217.St -ansiC 218with a lot of extensions including 219.Ql %C , 220.Ql %D , 221.Ql %E* , 222.Ql %e , 223.Ql %G , 224.Ql %g , 225.Ql %h , 226.Ql %k , 227.Ql %l , 228.Ql %n , 229.Ql %O* , 230.Ql \&%R , 231.Ql %r , 232.Ql %s , 233.Ql \&%T , 234.Ql %t , 235.Ql %u , 236.Ql \&%V , 237.Ql %+ . 238 239The peculiar week number and year in the replacements of 240.Ql %G , 241.Ql %g 242and 243.Ql \&%V 244are defined in ISO 8601: 1988. 245 246.Sh BUGS 247There is no conversion specification for the phase of the moon. 248