1 '\" te
   2 .\" Copyright (c) 2014 Gary Mills
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  13 .TH STRFTIME 3C "Jan 1, 2014"
  14 .SH NAME
  15 strftime, cftime, ascftime \- convert date and time to string
  16 .SH SYNOPSIS
  17 .LP
  18 .nf
  19 #include <time.h>
  20 
  21 \fBsize_t\fR \fBstrftime\fR(\fBchar *restrict\fR \fIs\fR, \fBsize_t\fR \fImaxsize\fR,
  22      \fBconst char *restrict\fR \fIformat\fR,
  23      \fBconst struct tm *restrict\fR \fItimeptr\fR);
  24 .fi
  25 
  26 .LP
  27 .nf
  28 \fBint\fR \fBcftime\fR(\fBchar *\fR\fIs\fR, \fBchar *\fR\fIformat\fR, \fBconst time_t *\fR\fIclock\fR);
  29 .fi
  30 
  31 .LP
  32 .nf
  33 \fBint\fR \fBascftime\fR(\fBchar *\fR\fIs\fR, \fBconst char *\fR\fIformat\fR,
  34      \fBconst struct tm *\fR\fItimeptr\fR);
  35 .fi
  36 
  37 .SH DESCRIPTION
  38 .sp
  39 .LP
  40 The \fBstrftime()\fR, \fBascftime()\fR, and \fBcftime()\fR functions place
  41 bytes into the array pointed to by \fIs\fR as controlled by the string pointed
  42 to by \fIformat\fR. The \fIformat\fR string consists of zero or more conversion
  43 specifications and ordinary characters.  A conversion specification consists of
  44 a '\fB%\fR' (percent) character and one or two terminating conversion
  45 characters that determine the conversion specification's behavior.  All
  46 ordinary characters (including the terminating null byte) are copied unchanged
  47 into the array pointed to by \fIs\fR. If copying takes place between objects
  48 that overlap, the behavior is undefined. For \fBstrftime()\fR, no more than
  49 \fImaxsize\fR bytes are placed into the array.
  50 .sp
  51 .LP
  52 If \fIformat\fR is \fB(char *)0\fR, then the locale's default format is used.
  53 For \fBstrftime()\fR the default format is the same as \fB%c\fR; for
  54 \fBcftime()\fR and \fBascftime()\fR the default format is the same as \fB%+\fR.
  55 \fBcftime()\fR and \fBascftime()\fR first try to use the value of the
  56 environment variable \fBCFTIME\fR, and if that is undefined or empty, the
  57 default format is used.
  58 .sp
  59 .LP
  60 Each conversion specification is replaced by appropriate characters as
  61 described in the following list. The appropriate characters are determined by
  62 the \fBLC_TIME\fR category of the program's locale and by the values contained
  63 in the structure pointed to by \fItimeptr\fR for \fBstrftime()\fR and
  64 \fBascftime()\fR, and by the time represented by \fIclock\fR for
  65 \fBcftime()\fR.
  66 .sp
  67 .ne 2
  68 .na
  69 \fB\fB%%\fR\fR
  70 .ad
  71 .RS 6n
  72 Same as \fB%\fR.
  73 .RE
  74 
  75 .sp
  76 .ne 2
  77 .na
  78 \fB\fB%a\fR\fR
  79 .ad
  80 .RS 6n
  81 Locale's abbreviated weekday name.
  82 .RE
  83 
  84 .sp
  85 .ne 2
  86 .na
  87 \fB\fB%A\fR\fR
  88 .ad
  89 .RS 6n
  90 Locale's full weekday name.
  91 .RE
  92 
  93 .sp
  94 .ne 2
  95 .na
  96 \fB\fB%b\fR\fR
  97 .ad
  98 .RS 6n
  99 Locale's abbreviated month name.
 100 .RE
 101 
 102 .sp
 103 .ne 2
 104 .na
 105 \fB\fB%B\fR\fR
 106 .ad
 107 .RS 6n
 108 Locale's full month name.
 109 .RE
 110 
 111 .sp
 112 .ne 2
 113 .na
 114 \fB\fB%c\fR\fR
 115 .ad
 116 .RS 6n
 117 Locale's appropriate date and time representation.
 118 .RE
 119 
 120 .sp
 121 .ne 2
 122 .na
 123 \fB\fB%C\fR\fR
 124 .ad
 125 .RS 6n
 126 Century number (the year divided by 100 and truncated to an integer as a
 127 decimal number [01,99]).
 128 .RE
 129 
 130 .sp
 131 .ne 2
 132 .na
 133 \fB\fB%d\fR\fR
 134 .ad
 135 .RS 6n
 136 Day of month [01,31].
 137 .RE
 138 
 139 .sp
 140 .ne 2
 141 .na
 142 \fB\fB%D\fR\fR
 143 .ad
 144 .RS 6n
 145 Date as \fB%m\fR/\fB%d\fR/\fB%y\fR.
 146 .RE
 147 
 148 .sp
 149 .ne 2
 150 .na
 151 \fB\fB%e\fR\fR
 152 .ad
 153 .RS 6n
 154 Day of month [1,31]; single  digits are preceded by a space.
 155 .RE
 156 
 157 .sp
 158 .ne 2
 159 .na
 160 \fB\fB%F\fR\fR
 161 .ad
 162 .RS 6n
 163 Equivalent to \fB%Y\fR-\fB%m\fR-\fB%d\fR (the ISO 8601:2000 standard date
 164 format).
 165 .RE
 166 
 167 .sp
 168 .ne 2
 169 .na
 170 \fB\fB%g\fR\fR
 171 .ad
 172 .RS 6n
 173 Week-based year within century [00,99].
 174 .RE
 175 
 176 .sp
 177 .ne 2
 178 .na
 179 \fB\fB%G\fR\fR
 180 .ad
 181 .RS 6n
 182 Week-based year, including the century [0000,9999].
 183 .RE
 184 
 185 .sp
 186 .ne 2
 187 .na
 188 \fB\fB%h\fR\fR
 189 .ad
 190 .RS 6n
 191 Locale's abbreviated month name.
 192 .RE
 193 
 194 .sp
 195 .ne 2
 196 .na
 197 \fB\fB%H\fR\fR
 198 .ad
 199 .RS 6n
 200 Hour (24-hour clock) [00,23].
 201 .RE
 202 
 203 .sp
 204 .ne 2
 205 .na
 206 \fB\fB%I\fR\fR
 207 .ad
 208 .RS 6n
 209 Hour (12-hour clock) [01,12].
 210 .RE
 211 
 212 .sp
 213 .ne 2
 214 .na
 215 \fB\fB%j\fR\fR
 216 .ad
 217 .RS 6n
 218 Day number of year [001,366].
 219 .RE
 220 
 221 .sp
 222 .ne 2
 223 .na
 224 \fB\fB%k\fR\fR
 225 .ad
 226 .RS 6n
 227 Hour (24-hour clock) [0,23]; single digits are preceded by a space.
 228 .RE
 229 
 230 .sp
 231 .ne 2
 232 .na
 233 \fB\fB%l\fR\fR
 234 .ad
 235 .RS 6n
 236 Hour (12-hour clock) [1,12]; single digits are preceded by a space.
 237 .RE
 238 
 239 .sp
 240 .ne 2
 241 .na
 242 \fB\fB%m\fR\fR
 243 .ad
 244 .RS 6n
 245 Month number [01,12].
 246 .RE
 247 
 248 .sp
 249 .ne 2
 250 .na
 251 \fB\fB%M\fR\fR
 252 .ad
 253 .RS 6n
 254 Minute [00,59].
 255 .RE
 256 
 257 .sp
 258 .ne 2
 259 .na
 260 \fB\fB%n\fR\fR
 261 .ad
 262 .RS 6n
 263 Insert a NEWLINE.
 264 .RE
 265 
 266 .sp
 267 .ne 2
 268 .na
 269 \fB\fB%p\fR\fR
 270 .ad
 271 .RS 6n
 272 Locale's equivalent of either a.m. or p.m.
 273 .RE
 274 
 275 .sp
 276 .ne 2
 277 .na
 278 \fB\fB%r\fR\fR
 279 .ad
 280 .RS 6n
 281 Appropriate time representation in 12-hour clock format with \fB%p\fR.
 282 .RE
 283 
 284 .sp
 285 .ne 2
 286 .na
 287 \fB\fB%R\fR\fR
 288 .ad
 289 .RS 6n
 290 Time as \fB%H\fR:\fB%M\fR.
 291 .RE
 292 
 293 .sp
 294 .ne 2
 295 .na
 296 \fB\fB%s\fR\fR
 297 .ad
 298 .RS 6n
 299 Seconds since 00:00:00 UTC, January 1, 1970.
 300 .RE
 301 
 302 .sp
 303 .ne 2
 304 .na
 305 \fB\fB%S\fR\fR
 306 .ad
 307 .RS 6n
 308 Seconds [00,60]; the range of values is [00,60] rather than [00,59] to allow
 309 for the occasional leap second.
 310 .RE
 311 
 312 .sp
 313 .ne 2
 314 .na
 315 \fB\fB%t\fR\fR
 316 .ad
 317 .RS 6n
 318 Insert a TAB.
 319 .RE
 320 
 321 .sp
 322 .ne 2
 323 .na
 324 \fB\fB%T\fR\fR
 325 .ad
 326 .RS 6n
 327 Time as \fB%H\fR:\fB%M\fR:\fB%S\fR.
 328 .RE
 329 
 330 .sp
 331 .ne 2
 332 .na
 333 \fB\fB%u\fR\fR
 334 .ad
 335 .RS 6n
 336 Weekday as a decimal number [1,7], with 1 representing Monday. See \fBNOTES\fR
 337 below.
 338 .RE
 339 
 340 .sp
 341 .ne 2
 342 .na
 343 \fB\fB%U\fR\fR
 344 .ad
 345 .RS 6n
 346 Week number of year as a decimal number [00,53], with Sunday as the first day
 347 of week 1.
 348 .RE
 349 
 350 .sp
 351 .ne 2
 352 .na
 353 \fB\fB%v\fR\fR
 354 .ad
 355 .RS 6n
 356 Date as \fB%e\fR-\fB%b\fR-\fB%Y\fR.
 357 .RE
 358 
 359 .sp
 360 .ne 2
 361 .na
 362 \fB\fB%V\fR\fR
 363 .ad
 364 .RS 6n
 365 The ISO 8601 week number as a decimal number [01,53]. In the ISO 8601
 366 week-based system, weeks begin on a Monday and week 1 of the year is the week
 367 that includes both January 4th and the first Thursday of the year.  If the
 368 first Monday of January is the 2nd, 3rd, or 4th, the preceding days are part of
 369 the last week of the preceding year.  See \fBNOTES\fR below.
 370 .RE
 371 
 372 .sp
 373 .ne 2
 374 .na
 375 \fB\fB%w\fR\fR
 376 .ad
 377 .RS 6n
 378 Weekday as a decimal number [0,6], with 0 representing Sunday.
 379 .RE
 380 
 381 .sp
 382 .ne 2
 383 .na
 384 \fB\fB%W\fR\fR
 385 .ad
 386 .RS 6n
 387 Week number of year as a decimal number [00,53], with Monday as the first day
 388 of week 1.
 389 .RE
 390 
 391 .sp
 392 .ne 2
 393 .na
 394 \fB\fB%x\fR\fR
 395 .ad
 396 .RS 6n
 397 Locale's appropriate date representation.
 398 .RE
 399 
 400 .sp
 401 .ne 2
 402 .na
 403 \fB\fB%X\fR\fR
 404 .ad
 405 .RS 6n
 406 Locale's appropriate time representation.
 407 .RE
 408 
 409 .sp
 410 .ne 2
 411 .na
 412 \fB\fB%y\fR\fR
 413 .ad
 414 .RS 6n
 415 Year within century [00,99].
 416 .RE
 417 
 418 .sp
 419 .ne 2
 420 .na
 421 \fB\fB%Y\fR\fR
 422 .ad
 423 .RS 6n
 424 Year, including the century (for example 1993).
 425 .RE
 426 
 427 .sp
 428 .ne 2
 429 .na
 430 \fB\fB%z\fR\fR
 431 .ad
 432 .RS 6n
 433 Replaced by offset from UTC in ISO 8601:2000 standard format (\fB+hhmm\fR or
 434 \fB-hhmm\fR), or by no characters if no time zone is determinable. For example,
 435 "-0430" means 4 hours 30 minutes behind UTC (west of Greenwich). If
 436 \fBtm_isdst\fR is zero, the standard time offset is used.  If \fBtm_isdst\fR is
 437 greater than zero, the daylight savings time offset if used. If \fBtm_isdst\fR
 438 is negative, no characters are returned.
 439 .RE
 440 
 441 .sp
 442 .ne 2
 443 .na
 444 \fB\fB%Z\fR\fR
 445 .ad
 446 .RS 6n
 447 Time zone name or abbreviation, or no bytes if no time zone information exists.
 448 .RE
 449 
 450 .sp
 451 .ne 2
 452 .na
 453 \fB\fB%+\fR\fR
 454 .ad
 455 .RS 6n
 456 Locale's date and time representation as produced by \fBdate\fR(1).
 457 .RE
 458 
 459 .sp
 460 .LP
 461 If a conversion specification does not correspond to any of the above or to any
 462 of the modified conversion specifications listed below, the behavior is
 463 undefined and \fB0\fR is returned.
 464 .sp
 465 .LP
 466 The difference between \fB%U\fR and \fB%W\fR (and also between modified
 467 conversion specifications \fB%OU\fR and \fB%OW\fR) lies in which day is counted
 468 as the first of the week. Week number 1 is the first week in January starting
 469 with a Sunday for \fB%U\fR or a Monday for \fB%W\fR. Week number 0 contains
 470 those days before the first Sunday or Monday in January for \fB%U\fR and
 471 \fB%W\fR, respectively.
 472 .SS "Modified Conversion Specifications"
 473 .sp
 474 .LP
 475 Some conversion specifications can be modified by the \fBE\fR and \fBO\fR
 476 modifiers to indicate that an alternate format or specification should be used
 477 rather than the one normally used by the unmodified conversion specification.
 478 If the alternate format or specification does not exist in the current locale,
 479 the behavior will be as if the unmodified specification were used.
 480 .sp
 481 .ne 2
 482 .na
 483 \fB\fB%Ec\fR\fR
 484 .ad
 485 .RS 7n
 486 Locale's alternate appropriate date and time representation.
 487 .RE
 488 
 489 .sp
 490 .ne 2
 491 .na
 492 \fB\fB%EC\fR\fR
 493 .ad
 494 .RS 7n
 495 Name of the base year (period) in the locale's alternate representation.
 496 .RE
 497 
 498 .sp
 499 .ne 2
 500 .na
 501 \fB\fB%Eg\fR\fR
 502 .ad
 503 .RS 7n
 504 Offset from \fB%EC\fR of the week-based year in the locale's alternative
 505 representation.
 506 .RE
 507 
 508 .sp
 509 .ne 2
 510 .na
 511 \fB\fB%EG\fR\fR
 512 .ad
 513 .RS 7n
 514 Full alternative representation of the week-based year.
 515 .RE
 516 
 517 .sp
 518 .ne 2
 519 .na
 520 \fB\fB%Ex\fR\fR
 521 .ad
 522 .RS 7n
 523 Locale's alternate date representation.
 524 .RE
 525 
 526 .sp
 527 .ne 2
 528 .na
 529 \fB\fB%EX\fR\fR
 530 .ad
 531 .RS 7n
 532 Locale's alternate time representation.
 533 .RE
 534 
 535 .sp
 536 .ne 2
 537 .na
 538 \fB\fB%Ey\fR\fR
 539 .ad
 540 .RS 7n
 541 Offset from \fB%EC\fR (year only) in the locale's alternate representation.
 542 .RE
 543 
 544 .sp
 545 .ne 2
 546 .na
 547 \fB\fB%EY\fR\fR
 548 .ad
 549 .RS 7n
 550 Full alternate year representation.
 551 .RE
 552 
 553 .sp
 554 .ne 2
 555 .na
 556 \fB\fB%Od\fR\fR
 557 .ad
 558 .RS 7n
 559 Day of the month using the locale's alternate numeric symbols.
 560 .RE
 561 
 562 .sp
 563 .ne 2
 564 .na
 565 \fB\fB%Oe\fR\fR
 566 .ad
 567 .RS 7n
 568 Same as \fB%Od\fR.
 569 .RE
 570 
 571 .sp
 572 .ne 2
 573 .na
 574 \fB\fB%Og\fR\fR
 575 .ad
 576 .RS 7n
 577 Week-based year (offset from \fB%C\fR) in the locale's alternate representation
 578 and using the locale's alternate numeric symbols.
 579 .RE
 580 
 581 .sp
 582 .ne 2
 583 .na
 584 \fB\fB%OH\fR\fR
 585 .ad
 586 .RS 7n
 587 Hour (24-hour clock) using the locale's alternate numeric symbols.
 588 .RE
 589 
 590 .sp
 591 .ne 2
 592 .na
 593 \fB\fB%OI\fR\fR
 594 .ad
 595 .RS 7n
 596 Hour (12-hour clock) using the locale's alternate numeric symbols.
 597 .RE
 598 
 599 .sp
 600 .ne 2
 601 .na
 602 \fB\fB%Om\fR\fR
 603 .ad
 604 .RS 7n
 605 Month using the locale's alternate numeric symbols.
 606 .RE
 607 
 608 .sp
 609 .ne 2
 610 .na
 611 \fB\fB%OM\fR\fR
 612 .ad
 613 .RS 7n
 614 Minutes using the locale's alternate numeric symbols.
 615 .RE
 616 
 617 .sp
 618 .ne 2
 619 .na
 620 \fB\fB%OS\fR\fR
 621 .ad
 622 .RS 7n
 623 Seconds using the locale's alternate numeric symbols.
 624 .RE
 625 
 626 .sp
 627 .ne 2
 628 .na
 629 \fB\fB%Ou\fR\fR
 630 .ad
 631 .RS 7n
 632 Weekday as a number in the locale's alternate numeric symbols.
 633 .RE
 634 
 635 .sp
 636 .ne 2
 637 .na
 638 \fB\fB%OU\fR\fR
 639 .ad
 640 .RS 7n
 641 Week number of the year (Sunday as the first day of the week) using the
 642 locale's alternate numeric symbols.
 643 .RE
 644 
 645 .sp
 646 .ne 2
 647 .na
 648 \fB\fB%Ow\fR\fR
 649 .ad
 650 .RS 7n
 651 Number of the weekday (Sunday=0) using the  locale's alternate numeric symbols.
 652 .RE
 653 
 654 .sp
 655 .ne 2
 656 .na
 657 \fB\fB%OW\fR\fR
 658 .ad
 659 .RS 7n
 660 Week number of the year (Monday as the first day of the week) using the
 661 locale's alternate numeric symbols.
 662 .RE
 663 
 664 .sp
 665 .ne 2
 666 .na
 667 \fB\fB%Oy\fR\fR
 668 .ad
 669 .RS 7n
 670 Year (offset from \fB%C\fR) in the locale's alternate representation and using
 671 the locale's alternate numeric symbols.
 672 .RE
 673 
 674 .SS "Selecting the Output Language"
 675 .sp
 676 .LP
 677 By default, the output of \fBstrftime()\fR, \fBcftime()\fR, and
 678 \fBascftime()\fR appear in U.S. English. The user can request that the output
 679 of \fBstrftime()\fR, \fBcftime()\fR, or \fBascftime()\fR be in a specific
 680 language by setting the \fBLC_TIME\fR category using \fBsetlocale()\fR.
 681 .SS "Time Zone"
 682 .sp
 683 .LP
 684 Local time zone information is used as though \fBtzset\fR(3C) were called.
 685 .SH RETURN VALUES
 686 .sp
 687 .LP
 688 The \fBstrftime()\fR, \fBcftime()\fR, and \fBascftime()\fR functions return the
 689 number of characters placed into the array pointed to by \fIs\fR, not including
 690 the terminating null character. If the total number of resulting characters
 691 including the terminating null character is more than \fImaxsize\fR,
 692 \fBstrftime()\fR returns \fB0\fR and the contents of the array are
 693 indeterminate.
 694 .SH EXAMPLES
 695 .LP
 696 \fBExample 1 \fRAn example of the \fBstrftime()\fR function.
 697 .sp
 698 .LP
 699 The following example illustrates the use of \fBstrftime()\fR for the
 700 \fBPOSIX\fR locale. It shows what the string in \fIstr\fR would look like if
 701 the structure pointed to by \fItmptr\fR contains the values corresponding to
 702 Thursday, August 28, 1986 at 12:44:36.
 703 
 704 .sp
 705 .in +2
 706 .nf
 707 \fBstrftime (str, strsize, "%A %b %d %j", tmptr)\fR
 708 .fi
 709 .in -2
 710 
 711 .sp
 712 .LP
 713 This results in \fIstr\fR containing "Thursday Aug 28 240".
 714 
 715 .SH ATTRIBUTES
 716 .sp
 717 .LP
 718 See \fBattributes\fR(5) for descriptions of the following attributes:
 719 .sp
 720 
 721 .sp
 722 .TS
 723 box;
 724 c | c
 725 l | l .
 726 ATTRIBUTE TYPE  ATTRIBUTE VALUE
 727 _
 728 CSI     Enabled
 729 _
 730 Interface Stability     Committed
 731 _
 732 MT-Level        MT-Safe
 733 _
 734 Standard        See below.
 735 .TE
 736 
 737 .sp
 738 .LP
 739 For \fBstrftime()\fR, see \fBstandards\fR(5).
 740 .SH SEE ALSO
 741 .sp
 742 .LP
 743 \fBdate\fR(1), \fBctime\fR(3C), \fBmktime\fR(3C), \fBsetlocale\fR(3C),
 744 \fBstrptime\fR(3C), \fBtzset\fR(3C), \fBTIMEZONE\fR(4), \fBzoneinfo\fR(4),
 745 \fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)
 746 .SH NOTES
 747 .sp
 748 .LP
 749 The conversion specification for \fB%V\fR was changed in the Solaris 7 release.
 750 This change was based on the public review draft of the ISO C9x standard at
 751 that time. Previously, the specification stated that if the week containing 1
 752 January had fewer than four days in the new year, it became week 53 of the
 753 previous year. The ISO C9x standard committee subsequently recognized that that
 754 specification had been incorrect.
 755 .sp
 756 .LP
 757 The conversion specifications for \fB%g\fR, \fB%G\fR, \fB%Eg\fR, \fB%EG\fR, and
 758 \fB%Og\fR were added in the Solaris 7 release.  This change was based on the
 759 public review draft of the ISO C9x standard at that time. These specifications
 760 are evolving.  If the ISO C9x standard is finalized with a different
 761 conclusion, these specifications will change to conform to the ISO C9x standard
 762 decision.
 763 .sp
 764 .LP
 765 The conversion specification for \fB%u\fR was changed in the Solaris 8 release.
 766 This change was based on the XPG4 specification.
 767 .sp
 768 .LP
 769 If using the \fB%Z\fR specifier and \fBzoneinfo\fR timezones and if the input
 770 date is outside the range 20:45:52 UTC, December  13, 1901 to 03:14:07 UTC,
 771 January 19, 2038, the timezone name may not be correct.