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 1.34 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 .Nm strftime_l
  45 .Nd format date and time
  46 .Sh LIBRARY
  47 .Lb libc
  48 .Sh SYNOPSIS
  49 .In time.h
  50 .Ft size_t
  51 .Fo strftime
  52 .Fa "char *restrict s"
  53 .Fa "size_t maxsize"
  54 .Fa "const char *restrict format"
  55 .Fa "const struct tm *restrict timeptr"
  56 .Fc
  57 .In time.h
  58 .In xlocale.h
  59 .Ft size_t
  60 .Fo strftime_l
  61 .Fa "char *restrict s"
  62 .Fa "size_t maxsize"
  63 .Fa "const char *restrict format"
  64 .Fa "const struct tm *restrict timeptr"
  65 .Fa "locale_t loc"
  66 .Fc
  67 .Sh DESCRIPTION
  68 The
  69 .Fn strftime
  70 function formats the information from
  71 .Fa timeptr
  72 into the buffer
  73 .Fa s ,
  74 according to the string pointed to by
  75 .Fa format .
  76 .Pp
  77 The
  78 .Fa format
  79 string consists of zero or more conversion specifications and
  80 ordinary characters.
  81 All ordinary characters are copied directly into the buffer.
  82 A conversion specification consists of a percent sign
  83 .Dq Ql %
  84 and one other character.
  85 .Pp
  86 No more than
  87 .Fa maxsize
  88 characters will be placed into the array.
  89 If the total number of resulting characters, including the terminating
  90 NUL character, is not more than
  91 .Fa maxsize ,
  92 .Fn strftime
  93 returns the number of characters in the array, not counting the
  94 terminating NUL.
  95 Otherwise, zero is returned and the buffer contents are indeterminate.
  96 .Pp
  97 Although the
  98 .Fn strftime
  99 function uses the current locale, the
 100 .Fn strftime_l
 101 function may be passed a locale directly. See
 102 .Xr xlocale 3
 103 for more information.
 104 .Pp
 105 The conversion specifications are copied to the buffer after expansion
 106 as follows:-
 107 .Bl -tag -width "xxxx"
 108 .It Cm \&%A
 109 is replaced by national representation of the full weekday name.
 110 .It Cm %a
 111 is replaced by national representation of
 112 the abbreviated weekday name.
 113 .It Cm \&%B
 114 is replaced by national representation of the full month name.
 115 .It Cm %b
 116 is replaced by national representation of
 117 the abbreviated month name.
 118 .It Cm \&%C
 119 is replaced by (year / 100) as decimal number; single
 120 digits are preceded by a zero.
 121 .It Cm %c
 122 is replaced by national representation of time and date.
 123 .It Cm \&%D
 124 is equivalent to
 125 .Dq Li %m/%d/%y .
 126 .It Cm %d
 127 is replaced by the day of the month as a decimal number (01-31).
 128 .It Cm \&%E* Cm \&%O*
 129 POSIX locale extensions.
 130 The sequences
 131 %Ec %EC %Ex %EX %Ey %EY
 132 %Od %Oe %OH %OI %Om %OM
 133 %OS %Ou %OU %OV %Ow %OW %Oy
 134 are supposed to provide alternate
 135 representations.
 136 .Pp
 137 Additionly %OB implemented
 138 to represent alternative months names
 139 (used standalone, without day mentioned).
 140 .It Cm %e
 141 is replaced by the day of month as a decimal number (1-31); single
 142 digits are preceded by a blank.
 143 .It Cm \&%F
 144 is equivalent to
 145 .Dq Li %Y-%m-%d .
 146 .It Cm \&%G
 147 is replaced by a year as a decimal number with century.
 148 This year is the one that contains the greater part of
 149 the week (Monday as the first day of the week).
 150 .It Cm %g
 151 is replaced by the same year as in
 152 .Dq Li %G ,
 153 but as a decimal number without century (00-99).
 154 .It Cm \&%H
 155 is replaced by the hour (24-hour clock) as a decimal number (00-23).
 156 .It Cm %h
 157 the same as %b.
 158 .It Cm \&%I
 159 is replaced by the hour (12-hour clock) as a decimal number (01-12).
 160 .It Cm %j
 161 is replaced by the day of the year as a decimal number (001-366).
 162 .It Cm %k
 163 is replaced by the hour (24-hour clock) as a decimal number (0-23);
 164 single digits are preceded by a blank.
 165 .It Cm %l
 166 is replaced by the hour (12-hour clock) as a decimal number (1-12);
 167 single digits are preceded by a blank.
 168 .It Cm \&%M
 169 is replaced by the minute as a decimal number (00-59).
 170 .It Cm %m
 171 is replaced by the month as a decimal number (01-12).
 172 .It Cm %n
 173 is replaced by a newline.
 174 .It Cm \&%O*
 175 the same as %E*.
 176 .It Cm %p
 177 is replaced by national representation of either
 178 "ante meridiem"
 179 or
 180 "post meridiem"
 181 as appropriate.
 182 .It Cm \&%R
 183 is equivalent to
 184 .Dq Li %H:%M .
 185 .It Cm %r
 186 is equivalent to
 187 .Dq Li %I:%M:%S %p .
 188 .It Cm \&%S
 189 is replaced by the second as a decimal number (00-60).
 190 .It Cm %s
 191 is replaced by the number of seconds since the Epoch, UTC (see
 192 .Xr mktime 3 ) .
 193 .It Cm \&%T
 194 is equivalent to
 195 .Dq Li %H:%M:%S .
 196 .It Cm %t
 197 is replaced by a tab.
 198 .It Cm \&%U
 199 is replaced by the week number of the year (Sunday as the first day of
 200 the week) as a decimal number (00-53).
 201 .It Cm %u
 202 is replaced by the weekday (Monday as the first day of the week)
 203 as a decimal number (1-7).
 204 .It Cm \&%V
 205 is replaced by the week number of the year (Monday as the first day of
 206 the week) as a decimal number (01-53).
 207 If the week containing January
 208 1 has four or more days in the new year, then it is week 1; otherwise
 209 it is the last week of the previous year, and the next week is week 1.
 210 .It Cm %v
 211 is equivalent to
 212 .Dq Li %e-%b-%Y .
 213 .It Cm \&%W
 214 is replaced by the week number of the year (Monday as the first day of
 215 the week) as a decimal number (00-53).
 216 .It Cm %w
 217 is replaced by the weekday (Sunday as the first day of the week)
 218 as a decimal number (0-6).
 219 .It Cm \&%X
 220 is replaced by national representation of the time.
 221 .It Cm %x
 222 is replaced by national representation of the date.
 223 .It Cm \&%Y
 224 is replaced by the year with century as a decimal number.
 225 .It Cm %y
 226 is replaced by the year without century as a decimal number (00-99).
 227 .It Cm \&%Z
 228 is replaced by the time zone name.
 229 .It Cm \&%z
 230 is replaced by the time zone offset from UTC; a leading plus sign stands for
 231 east of UTC, a minus sign for west of UTC, hours and minutes follow
 232 with two digits each and no delimiter between them (common form for
 233 RFC 822 date headers).
 234 .It Cm %+
 235 is replaced by national representation of the date and time
 236 (the format is similar to that produced by
 237 .Xr date 1 ) .
 238 .It Cm %%
 239 is replaced by
 240 .Ql % .
 241 .El
 242 .Sh SEE ALSO
 243 .Xr date 1 ,
 244 .Xr printf 1 ,
 245 .Xr ctime 3 ,
 246 .Xr printf 3 ,
 247 .Xr strptime 3 ,
 248 .Xr wcsftime 3 ,
 249 .Xr xlocale 3
 250 .Sh STANDARDS
 251 The
 252 .Fn strftime
 253 function
 254 conforms to
 255 .St -isoC
 256 with a lot of extensions including
 257 .Ql %C ,
 258 .Ql \&%D ,
 259 .Ql %E* ,
 260 .Ql %e ,
 261 .Ql %G ,
 262 .Ql %g ,
 263 .Ql %h ,
 264 .Ql %k ,
 265 .Ql %l ,
 266 .Ql %n ,
 267 .Ql %O* ,
 268 .Ql \&%R ,
 269 .Ql %r ,
 270 .Ql %s ,
 271 .Ql \&%T ,
 272 .Ql %t ,
 273 .Ql %u ,
 274 .Ql \&%V ,
 275 .Ql %z ,
 276 and
 277 .Ql %+ .
 278 .Pp
 279 The peculiar week number and year in the replacements of
 280 .Ql %G ,
 281 .Ql %g ,
 282 and
 283 .Ql \&%V
 284 are defined in ISO 8601: 1988.
 285 .Sh BUGS
 286 There is no conversion specification for the phase of the moon.
 287 .Pp
 288 The
 289 .Fn strftime
 290 function does not correctly handle multibyte characters in the
 291 .Fa format
 292 argument.