stdtime/FreeBSD/strftime.3

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  36 .\"     @(#)strftime.3  8.1 (Berkeley) 6/4/93
  37 .\" $FreeBSD: src/lib/libc/stdtime/strftime.3,v 1.34 2004/07/02 23:52:12 ru Exp $
  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
  57 The
  58 .Fn strftime
  59 function formats the information from
  60 .Fa timeptr
  61 into the buffer
  62 .Fa buf
  63 according to the string pointed to by
  64 .Fa format .
  65 .Pp
  66 The
  67 .Fa format
  68 string consists of zero or more conversion specifications and
  69 ordinary characters.
  70 All ordinary characters are copied directly into the buffer.
  71 A conversion specification consists of a percent sign
  72 .Dq Ql %
  73 and one other character.
  74 .Pp
  75 No more than
  76 .Fa maxsize
  77 characters will be placed into the array.
  78 If the total number of resulting characters, including the terminating
  79 NUL character, is not more than
  80 .Fa maxsize ,
  81 .Fn strftime
  82 returns the number of characters in the array, not counting the
  83 terminating NUL.
  84 Otherwise, zero is returned and the buffer contents are indeterminate.
  85 .Pp
  86 The conversion specifications are copied to the buffer after expansion
  87 as follows:-
  88 .Bl -tag -width "xxxx"
  89 .It Cm \&%A
  90 is replaced by national representation of the full weekday name.
  91 .It Cm %a
  92 is replaced by national representation of
  93 the abbreviated weekday name.
  94 .It Cm \&%B
  95 is replaced by national representation of the full month name.
  96 .It Cm %b
  97 is replaced by national representation of
  98 the abbreviated month name.
  99 .It Cm \&%C
 100 is replaced by (year / 100) as decimal number; single
 101 digits are preceded by a zero.
 102 .It Cm %c
 103 is replaced by national representation of time and date.
 104 .It Cm \&%D
 105 is equivalent to
 106 .Dq Li %m/%d/%y .
 107 .It Cm %d
 108 is replaced by the day of the month as a decimal number (01-31).
 109 .It Cm \&%E* Cm \&%O*
 110 POSIX locale extensions.
 111 The sequences
 112 %Ec %EC %Ex %EX %Ey %EY
 113 %Od %Oe %OH %OI %Om %OM
 114 %OS %Ou %OU %OV %Ow %OW %Oy
 115 are supposed to provide alternate
 116 representations.
 117 .Pp
 118 Additionly %OB implemented
 119 to represent alternative months names
 120 (used standalone, without day mentioned).
 121 .It Cm %e
 122 is replaced by the day of month as a decimal number (1-31); single
 123 digits are preceded by a blank.
 124 .It Cm \&%F
 125 is equivalent to
 126 .Dq Li %Y-%m-%d .
 127 .It Cm \&%G
 128 is replaced by a year as a decimal number with century.
 129 This year is the one that contains the greater part of
 130 the week (Monday as the first day of the week).
 131 .It Cm %g
 132 is replaced by the same year as in
 133 .Dq Li %G ,
 134 but as a decimal number without century (00-99).
 135 .It Cm \&%H
 136 is replaced by the hour (24-hour clock) as a decimal number (00-23).
 137 .It Cm %h
 138 the same as %b.
 139 .It Cm \&%I
 140 is replaced by the hour (12-hour clock) as a decimal number (01-12).
 141 .It Cm %j
 142 is replaced by the day of the year as a decimal number (001-366).
 143 .It Cm %k
 144 is replaced by the hour (24-hour clock) as a decimal number (0-23);
 145 single digits are preceded by a blank.
 146 .It Cm %l
 147 is replaced by the hour (12-hour clock) as a decimal number (1-12);
 148 single digits are preceded by a blank.
 149 .It Cm \&%M
 150 is replaced by the minute as a decimal number (00-59).
 151 .It Cm %m
 152 is replaced by the month as a decimal number (01-12).
 153 .It Cm %n
 154 is replaced by a newline.
 155 .It Cm \&%O*
 156 the same as %E*.
 157 .It Cm %p
 158 is replaced by national representation of either
 159 "ante meridiem"
 160 or
 161 "post meridiem"
 162 as appropriate.
 163 .It Cm \&%R
 164 is equivalent to
 165 .Dq Li %H:%M .
 166 .It Cm %r
 167 is equivalent to
 168 .Dq Li %I:%M:%S %p .
 169 .It Cm \&%S
 170 is replaced by the second as a decimal number (00-60).
 171 .It Cm %s
 172 is replaced by the number of seconds since the Epoch, UTC (see
 173 .Xr mktime 3 ) .
 174 .It Cm \&%T
 175 is equivalent to
 176 .Dq Li %H:%M:%S .
 177 .It Cm %t
 178 is replaced by a tab.
 179 .It Cm \&%U
 180 is replaced by the week number of the year (Sunday as the first day of
 181 the week) as a decimal number (00-53).
 182 .It Cm %u
 183 is replaced by the weekday (Monday as the first day of the week)
 184 as a decimal number (1-7).
 185 .It Cm \&%V
 186 is replaced by the week number of the year (Monday as the first day of
 187 the week) as a decimal number (01-53).
 188 If the week containing January
 189 1 has four or more days in the new year, then it is week 1; otherwise
 190 it is the last week of the previous year, and the next week is week 1.
 191 .It Cm %v
 192 is equivalent to
 193 .Dq Li %e-%b-%Y .
 194 .It Cm \&%W
 195 is replaced by the week number of the year (Monday as the first day of
 196 the week) as a decimal number (00-53).
 197 .It Cm %w
 198 is replaced by the weekday (Sunday as the first day of the week)
 199 as a decimal number (0-6).
 200 .It Cm \&%X
 201 is replaced by national representation of the time.
 202 .It Cm %x
 203 is replaced by national representation of the date.
 204 .It Cm \&%Y
 205 is replaced by the year with century as a decimal number.
 206 .It Cm %y
 207 is replaced by the year without century as a decimal number (00-99).
 208 .It Cm \&%Z
 209 is replaced by the time zone name.
 210 .It Cm \&%z
 211 is replaced by the time zone offset from UTC; a leading plus sign stands for
 212 east of UTC, a minus sign for west of UTC, hours and minutes follow
 213 with two digits each and no delimiter between them (common form for
 214 RFC 822 date headers).
 215 .It Cm %+
 216 is 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 %%
 220 is 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
 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.
 266 .Pp
 267 The
 268 .Fn strftime
 269 function does not correctly handle multibyte characters in the
 270 .Fa format
 271 argument.