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  46 .\" Copyright (c) 2014 Gary Mills
  47 .\" Copyright 2014 Garrett D'Amore <garrett@damore.org>
  48 .\"
  49 .TH STRFTIME 3C "Mar 30, 2019"
  50 .SH NAME
  51 strftime, strftime_l cftime, ascftime \- convert date and time to string
  52 .SH SYNOPSIS
  53 .LP
  54 .nf
  55 #include <time.h>
  56 
  57 \fBsize_t\fR \fBstrftime\fR(\fBchar *restrict\fR \fIs\fR, \fBsize_t\fR \fImaxsize\fR,
  58      \fBconst char *restrict\fR \fIformat\fR,
  59      \fBconst struct tm *restrict\fR \fItimeptr\fR);
  60 .fi
  61 .LP
  62 .nf
  63 \fBsize_t\fR \fBstrftime_l\fR(\fBchar *restrict\fR \fIs\fR, \fBsize_t\fR \fImaxsize\fR,
  64      \fBconst char *restrict\fR \fIformat\fR,
  65      \fBconst struct tm *restrict\fR \fItimeptr\fR, \fBlocale_t\fR \fIloc\fR);
  66 .fi
  67 .LP
  68 .nf
  69 \fBint\fR \fBcftime\fR(\fBchar *\fR\fIs\fR, \fBchar *\fR\fIformat\fR, \fBconst time_t *\fR\fIclock\fR);
  70 .fi
  71 .LP
  72 .nf
  73 \fBint\fR \fBascftime\fR(\fBchar *\fR\fIs\fR, \fBconst char *\fR\fIformat\fR,
  74      \fBconst struct tm *\fR\fItimeptr\fR);
  75 .fi
  76 
  77 .SH DESCRIPTION
  78 .LP
  79 The \fBstrftime()\fR, \fBstrftime_l()\fR, \fBascftime()\fR, and \fBcftime()\fR
  80 functions place
  81 bytes into the array pointed to by \fIs\fR as controlled by the string pointed
  82 to by \fIformat\fR. The \fIformat\fR string consists of zero or more conversion
  83 specifications and ordinary characters.  A conversion specification consists of
  84 a '\fB%\fR' (percent) character and one or two terminating conversion
  85 characters that determine the conversion specification's behavior.  All
  86 ordinary characters (including the terminating null byte) are copied unchanged
  87 into the array pointed to by \fIs\fR. If copying takes place between objects
  88 that overlap, the behavior is undefined. For \fBstrftime()\fR, no more than
  89 \fImaxsize\fR bytes are placed into the array. The \fBstrftime_l()\fR function
  90 behaves identically to \fBstrftime()\fR function, but instead of operating in
  91 the current locale, it operates in the locale specified by \fIloc\fR.
  92 .LP
  93 If \fIformat\fR is \fBNULL\fR, then the locale's default format is used.
  94 For \fBstrftime()\fR the default format is the same as \fB%c\fR; for
  95 \fBcftime()\fR and \fBascftime()\fR the default format is the same as \fB%+\fR.
  96 \fBcftime()\fR and \fBascftime()\fR first try to use the value of the
  97 environment variable \fBCFTIME\fR, and if that is undefined or empty, the
  98 default format is used.
  99 .LP
 100 Each conversion specification is replaced by appropriate characters as
 101 described in the following list. The appropriate characters are determined by
 102 the \fBLC_TIME\fR category of the program's locale and by the values contained
 103 in the structure pointed to by \fItimeptr\fR for \fBstrftime()\fR and
 104 \fBascftime()\fR, and by the time represented by \fIclock\fR for
 105 \fBcftime()\fR.
 106 .sp
 107 .ne 2
 108 .na
 109 \fB\fB%%\fR\fR
 110 .ad
 111 .RS 6n
 112 Same as \fB%\fR.
 113 .RE
 114 
 115 .sp
 116 .ne 2
 117 .na
 118 \fB\fB%a\fR\fR
 119 .ad
 120 .RS 6n
 121 Locale's abbreviated weekday name.
 122 .RE
 123 
 124 .sp
 125 .ne 2
 126 .na
 127 \fB\fB%A\fR\fR
 128 .ad
 129 .RS 6n
 130 Locale's full weekday name.
 131 .RE
 132 
 133 .sp
 134 .ne 2
 135 .na
 136 \fB\fB%b\fR\fR
 137 .ad
 138 .RS 6n
 139 Locale's abbreviated month name.
 140 .RE
 141 
 142 .sp
 143 .ne 2
 144 .na
 145 \fB\fB%B\fR\fR
 146 .ad
 147 .RS 6n
 148 Locale's full month name.
 149 .RE
 150 
 151 .sp
 152 .ne 2
 153 .na
 154 \fB\fB%c\fR\fR
 155 .ad
 156 .RS 6n
 157 Locale's appropriate date and time representation.
 158 In the C locale, this format is:
 159 .sp
 160 .in +2
 161 .nf
 162 %a %b %e %H:%M:%S %Y
 163 .fi
 164 .in -2
 165 .sp
 166 Other locales may have different locale-specific formats.
 167 .RE
 168 
 169 .sp
 170 .ne 2
 171 .na
 172 \fB\fB%C\fR\fR
 173 .ad
 174 .RS 6n
 175 Century number (the year divided by 100 and truncated to an integer as a
 176 decimal number [01,99]).
 177 .RE
 178 
 179 .sp
 180 .ne 2
 181 .na
 182 \fB\fB%d\fR\fR
 183 .ad
 184 .RS 6n
 185 Day of month [01,31].
 186 .RE
 187 
 188 .sp
 189 .ne 2
 190 .na
 191 \fB\fB%D\fR\fR
 192 .ad
 193 .RS 6n
 194 Date as \fB%m\fR/\fB%d\fR/\fB%y\fR.
 195 .RE
 196 
 197 .sp
 198 .ne 2
 199 .na
 200 \fB\fB%e\fR\fR
 201 .ad
 202 .RS 6n
 203 Day of month [1,31]; single  digits are preceded by a space.
 204 .RE
 205 
 206 .sp
 207 .ne 2
 208 .na
 209 \fB\fB%F\fR\fR
 210 .ad
 211 .RS 6n
 212 Equivalent to \fB%Y\fR-\fB%m\fR-\fB%d\fR (the ISO 8601:2000 standard date
 213 format).
 214 .RE
 215 
 216 .sp
 217 .ne 2
 218 .na
 219 \fB\fB%g\fR\fR
 220 .ad
 221 .RS 6n
 222 Week-based year within century [00,99].
 223 .RE
 224 
 225 .sp
 226 .ne 2
 227 .na
 228 \fB\fB%G\fR\fR
 229 .ad
 230 .RS 6n
 231 Week-based year, including the century [0000,9999].
 232 .RE
 233 
 234 .sp
 235 .ne 2
 236 .na
 237 \fB\fB%h\fR\fR
 238 .ad
 239 .RS 6n
 240 Locale's abbreviated month name.
 241 .RE
 242 
 243 .sp
 244 .ne 2
 245 .na
 246 \fB\fB%H\fR\fR
 247 .ad
 248 .RS 6n
 249 Hour (24-hour clock) [00,23].
 250 .RE
 251 
 252 .sp
 253 .ne 2
 254 .na
 255 \fB\fB%I\fR\fR
 256 .ad
 257 .RS 6n
 258 Hour (12-hour clock) [01,12].
 259 .RE
 260 
 261 .sp
 262 .ne 2
 263 .na
 264 \fB\fB%j\fR\fR
 265 .ad
 266 .RS 6n
 267 Day number of year [001,366].
 268 .RE
 269 
 270 .sp
 271 .ne 2
 272 .na
 273 \fB\fB%k\fR\fR
 274 .ad
 275 .RS 6n
 276 Hour (24-hour clock) [0,23]; single digits are preceded by a space.
 277 .RE
 278 
 279 .sp
 280 .ne 2
 281 .na
 282 \fB\fB%l\fR\fR
 283 .ad
 284 .RS 6n
 285 Hour (12-hour clock) [1,12]; single digits are preceded by a space.
 286 .RE
 287 
 288 .sp
 289 .ne 2
 290 .na
 291 \fB\fB%m\fR\fR
 292 .ad
 293 .RS 6n
 294 Month number [01,12].
 295 .RE
 296 
 297 .sp
 298 .ne 2
 299 .na
 300 \fB\fB%M\fR\fR
 301 .ad
 302 .RS 6n
 303 Minute [00,59].
 304 .RE
 305 
 306 .sp
 307 .ne 2
 308 .na
 309 \fB\fB%n\fR\fR
 310 .ad
 311 .RS 6n
 312 Insert a NEWLINE.
 313 .RE
 314 
 315 .sp
 316 .ne 2
 317 .na
 318 \fB\fB%p\fR\fR
 319 .ad
 320 .RS 6n
 321 Locale's equivalent of either a.m. or p.m.
 322 .RE
 323 
 324 .sp
 325 .ne 2
 326 .na
 327 \fB\fB%r\fR\fR
 328 .ad
 329 .RS 6n
 330 Appropriate time representation in 12-hour clock format with \fB%p\fR.
 331 .RE
 332 
 333 .sp
 334 .ne 2
 335 .na
 336 \fB\fB%R\fR\fR
 337 .ad
 338 .RS 6n
 339 Time as \fB%H\fR:\fB%M\fR.
 340 .RE
 341 
 342 .sp
 343 .ne 2
 344 .na
 345 \fB\fB%s\fR\fR
 346 .ad
 347 .RS 6n
 348 Seconds since 00:00:00 UTC, January 1, 1970.
 349 .RE
 350 
 351 .sp
 352 .ne 2
 353 .na
 354 \fB\fB%S\fR\fR
 355 .ad
 356 .RS 6n
 357 Seconds [00,60]; the range of values is [00,60] rather than [00,59] to allow
 358 for the occasional leap second.
 359 .RE
 360 
 361 .sp
 362 .ne 2
 363 .na
 364 \fB\fB%t\fR\fR
 365 .ad
 366 .RS 6n
 367 Insert a TAB.
 368 .RE
 369 
 370 .sp
 371 .ne 2
 372 .na
 373 \fB\fB%T\fR\fR
 374 .ad
 375 .RS 6n
 376 Time as \fB%H\fR:\fB%M\fR:\fB%S\fR.
 377 .RE
 378 
 379 .sp
 380 .ne 2
 381 .na
 382 \fB\fB%u\fR\fR
 383 .ad
 384 .RS 6n
 385 Weekday as a decimal number [1,7], with 1 representing Monday. See \fBNOTES\fR
 386 below.
 387 .RE
 388 
 389 .sp
 390 .ne 2
 391 .na
 392 \fB\fB%U\fR\fR
 393 .ad
 394 .RS 6n
 395 Week number of year as a decimal number [00,53], with Sunday as the first day
 396 of week 1.
 397 .RE
 398 
 399 .sp
 400 .ne 2
 401 .na
 402 \fB\fB%v\fR\fR
 403 .ad
 404 .RS 6n
 405 Date as \fB%e\fR-\fB%b\fR-\fB%Y\fR.
 406 .RE
 407 
 408 .sp
 409 .ne 2
 410 .na
 411 \fB\fB%V\fR\fR
 412 .ad
 413 .RS 6n
 414 The ISO 8601 week number as a decimal number [01,53]. In the ISO 8601
 415 week-based system, weeks begin on a Monday and week 1 of the year is the week
 416 that includes both January 4th and the first Thursday of the year.  If the
 417 first Monday of January is the 2nd, 3rd, or 4th, the preceding days are part of
 418 the last week of the preceding year.  See \fBNOTES\fR below.
 419 .RE
 420 
 421 .sp
 422 .ne 2
 423 .na
 424 \fB\fB%w\fR\fR
 425 .ad
 426 .RS 6n
 427 Weekday as a decimal number [0,6], with 0 representing Sunday.
 428 .RE
 429 
 430 .sp
 431 .ne 2
 432 .na
 433 \fB\fB%W\fR\fR
 434 .ad
 435 .RS 6n
 436 Week number of year as a decimal number [00,53], with Monday as the first day
 437 of week 1.
 438 .RE
 439 
 440 .sp
 441 .ne 2
 442 .na
 443 \fB\fB%x\fR\fR
 444 .ad
 445 .RS 6n
 446 Locale's appropriate date representation.
 447 .RE
 448 
 449 .sp
 450 .ne 2
 451 .na
 452 \fB\fB%X\fR\fR
 453 .ad
 454 .RS 6n
 455 Locale's appropriate time representation.
 456 .RE
 457 
 458 .sp
 459 .ne 2
 460 .na
 461 \fB\fB%y\fR\fR
 462 .ad
 463 .RS 6n
 464 Year within century [00,99].
 465 .RE
 466 
 467 .sp
 468 .ne 2
 469 .na
 470 \fB\fB%Y\fR\fR
 471 .ad
 472 .RS 6n
 473 Year, including the century (for example 1993).
 474 .RE
 475 
 476 .sp
 477 .ne 2
 478 .na
 479 \fB\fB%z\fR\fR
 480 .ad
 481 .RS 6n
 482 Replaced by offset from UTC in ISO 8601:2000 standard format (\fB+hhmm\fR or
 483 \fB-hhmm\fR), or by no characters if no time zone is determinable. For example,
 484 "-0430" means 4 hours 30 minutes behind UTC (west of Greenwich). If
 485 \fBtm_isdst\fR is zero, the standard time offset is used.  If \fBtm_isdst\fR is
 486 greater than zero, the daylight savings time offset if used. If \fBtm_isdst\fR
 487 is negative, no characters are returned.
 488 .RE
 489 
 490 .sp
 491 .ne 2
 492 .na
 493 \fB\fB%Z\fR\fR
 494 .ad
 495 .RS 6n
 496 Time zone name or abbreviation, or no bytes if no time zone information exists.
 497 .RE
 498 
 499 .sp
 500 .ne 2
 501 .na
 502 \fB\fB%+\fR\fR
 503 .ad
 504 .RS 6n
 505 Locale's date and time representation as produced by \fBdate\fR(1).
 506 .RE
 507 
 508 .LP
 509 If a conversion specification does not correspond to any of the above or to any
 510 of the modified conversion specifications listed below, the behavior is
 511 undefined and \fB0\fR is returned.
 512 .LP
 513 The difference between \fB%U\fR and \fB%W\fR (and also between modified
 514 conversion specifications \fB%OU\fR and \fB%OW\fR) lies in which day is counted
 515 as the first of the week. Week number 1 is the first week in January starting
 516 with a Sunday for \fB%U\fR or a Monday for \fB%W\fR. Week number 0 contains
 517 those days before the first Sunday or Monday in January for \fB%U\fR and
 518 \fB%W\fR, respectively.
 519 .SS "Modified Conversion Specifications"
 520 .LP
 521 Some conversion specifications can be modified by the \fBE\fR and \fBO\fR
 522 modifiers to indicate that an alternate format or specification should be used
 523 rather than the one normally used by the unmodified conversion specification.
 524 If the alternate format or specification does not exist in the current locale,
 525 the behavior will be as if the unmodified specification were used.
 526 .sp
 527 .ne 2
 528 .na
 529 \fB\fB%Ec\fR\fR
 530 .ad
 531 .RS 7n
 532 Locale's alternate appropriate date and time representation.
 533 .RE
 534 
 535 .sp
 536 .ne 2
 537 .na
 538 \fB\fB%EC\fR\fR
 539 .ad
 540 .RS 7n
 541 Name of the base year (period) in the locale's alternate representation.
 542 .RE
 543 
 544 .sp
 545 .ne 2
 546 .na
 547 \fB\fB%Eg\fR\fR
 548 .ad
 549 .RS 7n
 550 Offset from \fB%EC\fR of the week-based year in the locale's alternative
 551 representation.
 552 .RE
 553 
 554 .sp
 555 .ne 2
 556 .na
 557 \fB\fB%EG\fR\fR
 558 .ad
 559 .RS 7n
 560 Full alternative representation of the week-based year.
 561 .RE
 562 
 563 .sp
 564 .ne 2
 565 .na
 566 \fB\fB%Ex\fR\fR
 567 .ad
 568 .RS 7n
 569 Locale's alternate date representation.
 570 .RE
 571 
 572 .sp
 573 .ne 2
 574 .na
 575 \fB\fB%EX\fR\fR
 576 .ad
 577 .RS 7n
 578 Locale's alternate time representation.
 579 .RE
 580 
 581 .sp
 582 .ne 2
 583 .na
 584 \fB\fB%Ey\fR\fR
 585 .ad
 586 .RS 7n
 587 Offset from \fB%EC\fR (year only) in the locale's alternate representation.
 588 .RE
 589 
 590 .sp
 591 .ne 2
 592 .na
 593 \fB\fB%EY\fR\fR
 594 .ad
 595 .RS 7n
 596 Full alternate year representation.
 597 .RE
 598 
 599 .sp
 600 .ne 2
 601 .na
 602 \fB\fB%Od\fR\fR
 603 .ad
 604 .RS 7n
 605 Day of the month using the locale's alternate numeric symbols.
 606 .RE
 607 
 608 .sp
 609 .ne 2
 610 .na
 611 \fB\fB%Oe\fR\fR
 612 .ad
 613 .RS 7n
 614 Same as \fB%Od\fR.
 615 .RE
 616 
 617 .sp
 618 .ne 2
 619 .na
 620 \fB\fB%Og\fR\fR
 621 .ad
 622 .RS 7n
 623 Week-based year (offset from \fB%C\fR) in the locale's alternate representation
 624 and using the locale's alternate numeric symbols.
 625 .RE
 626 
 627 .sp
 628 .ne 2
 629 .na
 630 \fB\fB%OH\fR\fR
 631 .ad
 632 .RS 7n
 633 Hour (24-hour clock) using the locale's alternate numeric symbols.
 634 .RE
 635 
 636 .sp
 637 .ne 2
 638 .na
 639 \fB\fB%OI\fR\fR
 640 .ad
 641 .RS 7n
 642 Hour (12-hour clock) using the locale's alternate numeric symbols.
 643 .RE
 644 
 645 .sp
 646 .ne 2
 647 .na
 648 \fB\fB%Om\fR\fR
 649 .ad
 650 .RS 7n
 651 Month using the locale's alternate numeric symbols.
 652 .RE
 653 
 654 .sp
 655 .ne 2
 656 .na
 657 \fB\fB%OM\fR\fR
 658 .ad
 659 .RS 7n
 660 Minutes using the locale's alternate numeric symbols.
 661 .RE
 662 
 663 .sp
 664 .ne 2
 665 .na
 666 \fB\fB%OS\fR\fR
 667 .ad
 668 .RS 7n
 669 Seconds using the locale's alternate numeric symbols.
 670 .RE
 671 
 672 .sp
 673 .ne 2
 674 .na
 675 \fB\fB%Ou\fR\fR
 676 .ad
 677 .RS 7n
 678 Weekday as a number in the locale's alternate numeric symbols.
 679 .RE
 680 
 681 .sp
 682 .ne 2
 683 .na
 684 \fB\fB%OU\fR\fR
 685 .ad
 686 .RS 7n
 687 Week number of the year (Sunday as the first day of the week) using the
 688 locale's alternate numeric symbols.
 689 .RE
 690 
 691 .sp
 692 .ne 2
 693 .na
 694 \fB\fB%Ow\fR\fR
 695 .ad
 696 .RS 7n
 697 Number of the weekday (Sunday=0) using the  locale's alternate numeric symbols.
 698 .RE
 699 
 700 .sp
 701 .ne 2
 702 .na
 703 \fB\fB%OW\fR\fR
 704 .ad
 705 .RS 7n
 706 Week number of the year (Monday as the first day of the week) using the
 707 locale's alternate numeric symbols.
 708 .RE
 709 
 710 .sp
 711 .ne 2
 712 .na
 713 \fB\fB%Oy\fR\fR
 714 .ad
 715 .RS 7n
 716 Year (offset from \fB%C\fR) in the locale's alternate representation and using
 717 the locale's alternate numeric symbols.
 718 .RE
 719 
 720 .SS "Selecting the Output Language"
 721 .LP
 722 These routines produce output that is formatted according to the \fBLC_TIME\fR
 723 locale category.  They use either the current locale, or in the case of
 724 \fBstrftime_l()\fR, the locale supplied by \fIloc\fR.
 725 .SS "Time Zone"
 726 .LP
 727 Local time zone information is used as though \fBtzset\fR(3C) were called.
 728 .SH RETURN VALUES
 729 .LP
 730 These functions return the
 731 number of characters placed into the array pointed to by \fIs\fR, not including
 732 the terminating null character. If the total number of resulting characters
 733 including the terminating null character is more than \fImaxsize\fR,
 734 \fBstrftime()\fR returns \fB0\fR and the contents of the array are
 735 indeterminate.
 736 .SH EXAMPLES
 737 .LP
 738 \fBExample 1 \fRAn example of the \fBstrftime()\fR function.
 739 .LP
 740 The following example illustrates the use of \fBstrftime()\fR for the
 741 \fBPOSIX\fR locale. It shows what the string in \fIstr\fR would look like if
 742 the structure pointed to by \fItmptr\fR contains the values corresponding to
 743 Thursday, August 28, 1986 at 12:44:36.
 744 .nf
 745 .IP
 746 \fBstrftime\fR(\fIstr\fR, \fIstrsize\fR, "%A %b %d %j", \fItmptr\fR);
 747 .fi
 748 .LP
 749 This results in \fIstr\fR containing "Thursday Aug 28 240".
 750 .SH ATTRIBUTES
 751 .LP
 752 See \fBattributes\fR(5) for descriptions of the following attributes:
 753 .TS
 754 box;
 755 c | c
 756 l | l .
 757 ATTRIBUTE TYPE  ATTRIBUTE VALUE
 758 _
 759 CSI     Enabled
 760 _
 761 Interface Stability     See below.
 762 _
 763 MT-Level        MT-Safe
 764 _
 765 Standard        See below.
 766 .TE
 767 
 768 .LP
 769 The \fBstrftime()\fR and \fBstrftime_l()\fR functions are Standard.
 770 \fBcftime()\fR and \fBascftime()\fR functions are Committed.
 771 .LP
 772 For \fBstrftime()\fR and \fBstrftime_l()\fR, see \fBstandards\fR(5).
 773 .SH SEE ALSO
 774 .LP
 775 \fBdate\fR(1), \fBctime\fR(3C), \fBmktime\fR(3C),
 776 \fBnewlocale\fR(3C), \fBsetlocale\fR(3C), \fBstrptime\fR(3C), \fBtzset\fR(3C),
 777 \fBuselocale\fR(3C), \fBTIMEZONE\fR(4), \fBzoneinfo\fR(4),
 778 \fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)
 779 .SH NOTES
 780 .LP
 781 The conversion specification for \fB%V\fR was changed in the Solaris 7 release.
 782 This change was based on the public review draft of the ISO C9x standard at
 783 that time. Previously, the specification stated that if the week containing 1
 784 January had fewer than four days in the new year, it became week 53 of the
 785 previous year. The ISO C9x standard committee subsequently recognized that that
 786 specification had been incorrect.
 787 .LP
 788 The conversion specifications for \fB%g\fR, \fB%G\fR, \fB%Eg\fR, \fB%EG\fR, and
 789 \fB%Og\fR were added in the Solaris 7 release.  This change was based on the
 790 public review draft of the ISO C9x standard at that time. The \fB%g\fR and
 791 \fB%G\fR specifications were adopted in the formal standard.  The other two
 792 were not, and should not be used in portable applications.
 793 .LP
 794 The conversion specification for \fB%u\fR was changed in the Solaris 8 release.
 795 This change was based on the XPG4 specification.
 796 .LP
 797 If using the \fB%Z\fR specifier and \fBzoneinfo\fR timezones and if the input
 798 date is outside the range 20:45:52 UTC, December  13, 1901 to 03:14:07 UTC,
 799 January 19, 2038, the timezone name may not be correct.
 800 .LP
 801 The conversion specification for \fB%+\fR was added in illumos.
 802 It is not part of any standard, although it is available on a number
 803 of other platforms.
 804 Its use is discouraged for conforming applications.