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. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.Dd June 25, 2012 33.Dt STRFTIME 3 34.Os 35.Sh NAME 36.Nm strftime 37.Nd format date and time 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In time.h 42.Ft size_t 43.Fo strftime 44.Fa "char * restrict buf" 45.Fa "size_t maxsize" 46.Fa "const char * restrict format" 47.Fa "const struct tm * restrict timeptr" 48.Fc 49.Ft size_t 50.Fn strftime_l "char *restrict buf" "size_t maxsize" "const char * restrict format" "const struct tm *restrict timeptr" "locale_t loc" 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 . 60The function 61.Fn strftime_l 62does the same as 63.Fn strftime 64but takes an explicit locale rather than using the current locale. 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* %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 118Additionally %OB implemented 119to represent alternative months names 120(used standalone, without day mentioned). 121.It Cm %e 122is replaced by the day of the 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 139.Cm %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 158.Cm %E* . 159.It Cm %p 160is replaced by national representation of either 161"ante meridiem" (a.m.) 162or 163"post meridiem" (p.m.) 164as appropriate. 165.It Cm \&%R 166is equivalent to 167.Dq Li %H:%M . 168.It Cm %r 169is equivalent to 170.Dq Li %I:%M:%S %p . 171.It Cm \&%S 172is replaced by the second as a decimal number (00-60). 173.It Cm %s 174is replaced by the number of seconds since the Epoch, UTC (see 175.Xr mktime 3 ) . 176.It Cm \&%T 177is equivalent to 178.Dq Li %H:%M:%S . 179.It Cm %t 180is replaced by a tab. 181.It Cm \&%U 182is replaced by the week number of the year (Sunday as the first day of 183the week) as a decimal number (00-53). 184.It Cm %u 185is replaced by the weekday (Monday as the first day of the week) 186as a decimal number (1-7). 187.It Cm \&%V 188is replaced by the week number of the year (Monday as the first day of 189the week) as a decimal number (01-53). 190If the week containing January 1911 has four or more days in the new year, then it is week 1; otherwise 192it is the last week of the previous year, and the next week is week 1. 193.It Cm %v 194is equivalent to 195.Dq Li %e-%b-%Y . 196.It Cm \&%W 197is replaced by the week number of the year (Monday as the first day of 198the week) as a decimal number (00-53). 199.It Cm %w 200is replaced by the weekday (Sunday as the first day of the week) 201as a decimal number (0-6). 202.It Cm \&%X 203is replaced by national representation of the time. 204.It Cm %x 205is replaced by national representation of the date. 206.It Cm \&%Y 207is replaced by the year with century as a decimal number. 208.It Cm %y 209is replaced by the year without century as a decimal number (00-99). 210.It Cm \&%Z 211is replaced by the time zone name. 212.It Cm %z 213is replaced by the time zone offset from UTC; a leading plus sign stands for 214east of UTC, a minus sign for west of UTC, hours and minutes follow 215with two digits each and no delimiter between them (common form for 216RFC 822 date headers). 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 %-* 222GNU libc extension. 223Do not do any padding when performing numerical outputs. 224.It Cm %_* 225GNU libc extension. 226Explicitly specify space for padding. 227.It Cm %0* 228GNU libc extension. 229Explicitly specify zero for padding. 230.It Cm %% 231is replaced by 232.Ql % . 233.El 234.Sh SEE ALSO 235.Xr date 1 , 236.Xr printf 1 , 237.Xr ctime 3 , 238.Xr printf 3 , 239.Xr strptime 3 , 240.Xr wcsftime 3 241.Sh STANDARDS 242The 243.Fn strftime 244function 245conforms to 246.St -isoC 247with a lot of extensions including 248.Ql \&%C , 249.Ql \&%D , 250.Ql %E* , 251.Ql %e , 252.Ql %G , 253.Ql %g , 254.Ql %h , 255.Ql %k , 256.Ql %l , 257.Ql %n , 258.Ql %O* , 259.Ql \&%R , 260.Ql %r , 261.Ql %s , 262.Ql \&%T , 263.Ql %t , 264.Ql %u , 265.Ql \&%V , 266.Ql %z , 267.Ql %+ . 268.Pp 269The peculiar week number and year in the replacements of 270.Ql %G , 271.Ql %g 272and 273.Ql \&%V 274are defined in 275.St -iso8601 . 276The 277.Fn strftime_l 278function conforms to 279.St -p1003.1-2008 . 280.Sh BUGS 281There is no conversion specification for the phase of the moon. 282.Pp 283The 284.Fn strftime 285function does not correctly handle multibyte characters in the 286.Fa format 287argument. 288