stdtime/strftime.3

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  36 .\"     @(#)strftime.3  8.1 (Berkeley) 6/4/93
  37 .\" $FreeBSD: src/lib/libc/stdtime/strftime.3,v 1.18.2.7 2001/12/14 18:33:59 ru Exp $
  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
  52 The
  53 .Fn strftime
  54 function formats the information from
  55 .Fa timeptr
  56 into the buffer
  57 .Fa buf
  58 according to the string pointed to by
  59 .Fa format .
  60 .Pp
  61 The
  62 .Fa format
  63 string consists of zero or more conversion specifications and
  64 ordinary characters.
  65 All ordinary characters are copied directly into the buffer.
  66 A conversion specification consists of a percent sign
  67 .Dq Ql %
  68 and one other character.
  69 .Pp
  70 No more than
  71 .Fa maxsize
  72 characters will be placed into the array.
  73 If the total number of resulting characters, including the terminating
  74 NUL character, is not more than
  75 .Fa maxsize ,
  76 .Fn strftime
  77 returns the number of characters in the array, not counting the
  78 terminating NUL.
  79 Otherwise, zero is returned and the buffer contents is indeterminate.
  80 .Pp
  81 The conversion specifications are copied to the buffer after expansion
  82 as follows:-
  83 .Bl -tag -width "xxxx"
  84 .It Cm \&%A
  85 is replaced by national representation of the full weekday name.
  86 .It Cm %a
  87 is replaced by national representation of
  88 the abbreviated weekday name, where the abbreviation
  89 is the first three characters.
  90 .It Cm \&%B
  91 is replaced by national representation of the full month name.
  92 .It Cm %b
  93 is replaced by national representation of
  94 the abbreviated month name, where the abbreviation is
  95 the first three characters.
  96 .It Cm \&%C
  97 is replaced by (year / 100) as decimal number; single
  98 digits are preceded by a zero.
  99 .It Cm %c
 100 is replaced by national representation of time and date.
 101 The format is similar to that produced by
 102 .Xr ctime 3
 103 and is
 104 equivalent to "%a %Ef %T %Y".
 105 It also implies the
 106 "3+1+6+1+8+1+4" format of output.
 107 .It Cm \&%D
 108 is equivalent to
 109 .Dq Li %m/%d/%y .
 110 .It Cm %d
 111 is replaced by the day of the month as a decimal number (01-31).
 112 .It Cm \&%E* Cm \&%O*
 113 POSIX locale extensions.
 114 The sequences
 115 %Ec %EC %Ex %EX %Ey %EY
 116 %Od %Oe %OH %OI %Om %OM
 117 %OS %Ou %OU %OV %Ow %OW %Oy
 118 are supposed to provide alternate
 119 representations.
 120 .Pp
 121 Additionly %Ef implemented to represent short month name / day
 122 order of the date, %EF to represent long month name / day
 123 order
 124 and %OB to represent alternative months names
 125 (used standalone, without day mentioned).
 126 .It Cm %e
 127 is replaced by the day of month as a decimal number (1-31); single
 128 digits are preceded by a blank.
 129 .It Cm \&%G
 130 is replaced by a year as a decimal number with century.
 131 This year is the one that contains the greater part of
 132 the week (Monday as the first day of the week).
 133 .It Cm %g
 134 is replaced by the same year as in
 135 .Dq Li %G ,
 136 but as a decimal number without century (00-99).
 137 .It Cm \&%H
 138 is replaced by the hour (24-hour clock) as a decimal number (00-23).
 139 .It Cm %h
 140 the same as %b.
 141 .It Cm \&%I
 142 is replaced by the hour (12-hour clock) as a decimal number (01-12).
 143 .It Cm %j
 144 is replaced by the day of the year as a decimal number (001-366).
 145 .It Cm %k
 146 is replaced by the hour (24-hour clock) as a decimal number (0-23);
 147 single digits are preceded by a blank.
 148 .It Cm %l
 149 is replaced by the hour (12-hour clock) as a decimal number (1-12);
 150 single digits are preceded by a blank.
 151 .It Cm \&%M
 152 is replaced by the minute as a decimal number (00-59).
 153 .It Cm %m
 154 is replaced by the month as a decimal number (01-12).
 155 .It Cm %n
 156 is replaced by a newline.
 157 .It Cm \&%O*
 158 the same as %E*.
 159 .It Cm %p
 160 is replaced by national representation of either
 161 "ante meridiem"
 162 or
 163 "post meridiem"
 164 as appropriate.
 165 .It Cm \&%R
 166 is equivalent to
 167 .Dq Li %H:%M .
 168 .It Cm %r
 169 is equivalent to
 170 .Dq Li %I:%M:%S %p .
 171 .It Cm \&%S
 172 is replaced by the second as a decimal number (00-60).
 173 .It Cm %s
 174 is replaced by the number of seconds since the Epoch, UTC (see
 175 .Xr mktime 3 ) .
 176 .It Cm \&%T
 177 is equivalent to
 178 .Dq Li %H:%M:%S .
 179 .It Cm %t
 180 is replaced by a tab.
 181 .It Cm \&%U
 182 is replaced by the week number of the year (Sunday as the first day of
 183 the week) as a decimal number (00-53).
 184 .It Cm %u
 185 is replaced by the weekday (Monday as the first day of the week)
 186 as a decimal number (1-7).
 187 .It Cm \&%V
 188 is replaced by the week number of the year (Monday as the first day of
 189 the week) as a decimal number (01-53).  If the week containing January
 190 1 has four or more days in the new year, then it is week 1; otherwise
 191 it is the last week of the previous year, and the next week is week 1.
 192 .It Cm %v
 193 is equivalent to
 194 .Dq Li %e-%b-%Y .
 195 .It Cm \&%W
 196 is replaced by the week number of the year (Monday as the first day of
 197 the week) as a decimal number (00-53).
 198 .It Cm %w
 199 is replaced by the weekday (Sunday as the first day of the week)
 200 as a decimal number (0-6).
 201 .It Cm \&%X
 202 is replaced by national representation of the time.
 203 .It Cm %x
 204 is replaced by national representation of the date.
 205 .It Cm \&%Y
 206 is replaced by the year with century as a decimal number.
 207 .It Cm %y
 208 is replaced by the year without century as a decimal number (00-99).
 209 .It Cm \&%Z
 210 is replaced by the time zone name.
 211 .It Cm \&%z
 212 is replaced by the time zone offset from UTC; a leading plus sign stands for
 213 east of UTC, a minus sign for west of UTC, hours and minutes follow
 214 with two digits each and no delimiter between them (common form for
 215 RFC 822 date headers).
 216 .It Cm %+
 217 is replaced by national representation of the date and time
 218 (the format is similar to that produced by
 219 .Xr date 1 ) .
 220 .It Cm %%
 221 is replaced by
 222 .Ql % .
 223 .El
 224 .Sh SEE ALSO
 225 .Xr date 1 ,
 226 .Xr printf 1 ,
 227 .Xr ctime 3 ,
 228 .Xr printf 3 ,
 229 .Xr strptime 3
 230 .Sh STANDARDS
 231 The
 232 .Fn strftime
 233 function
 234 conforms to
 235 .St -isoC
 236 with 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
 258 The peculiar week number and year in the replacements of
 259 .Ql %G ,
 260 .Ql %g
 261 and
 262 .Ql \&%V
 263 are defined in ISO 8601: 1988.
 264 .Sh BUGS
 265 There is no conversion specification for the phase of the moon.