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