| blob | 6cb6cdde8c60b6b9128a5d91fe4a5e0faf0e7b39 |
1 .\" Copyright (c) 2020 by Alejandro Colomar <colomar.6.4.3@gmail.com>
2 .\" and Copyright (c) 2020 by Michael Kerrisk <mtk.manpages@gmail.com>
3 .\"
4 .\" %%%LICENSE_START(VERBATIM)
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
8 .\"
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
13 .\"
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
20 .\" professionally.
21 .\"
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
24 .\" %%%LICENSE_END
25 .\"
26 .\"
27 .TH SYSTEM_DATA_TYPES 7 2021-03-22 "Linux" "Linux Programmer's Manual"
28 .SH NAME
29 system_data_types \- overview of system data types
30 .SH DESCRIPTION
31 .\" Layout:
32 .\" A list of type names (the struct/union keyword will be omitted).
33 .\" Each entry will have the following parts:
34 .\" * Include (see NOTES)
35 .\"
36 .\" * Definition (no "Definition" header)
37 .\" Only struct/union types will have definition;
38 .\" typedefs will remain opaque.
39 .\"
40 .\" * Description (no "Description" header)
41 .\" A few lines describing the type.
42 .\"
43 .\" * Versions (optional)
44 .\"
45 .\" * Conforming to (see NOTES)
46 .\" Format: CXY and later; POSIX.1-XXXX and later.
47 .\"
48 .\" * Notes (optional)
49 .\"
50 .\" * Bugs (if any)
51 .\"
52 .\" * See also
53 .\"------------------------------------- aiocb ------------------------/
54 .TP
55 .I aiocb
56 .RS
57 .IR Include :
58 .IR <aio.h> .
59 .PP
60 .EX
61 struct aiocb {
62 int aio_fildes; /* File descriptor */
63 off_t aio_offset; /* File offset */
64 volatile void *aio_buf; /* Location of buffer */
65 size_t aio_nbytes; /* Length of transfer */
66 int aio_reqprio; /* Request priority offset */
67 struct sigevent aio_sigevent; /* Signal number and value */
68 int aio_lio_opcode;/* Operation to be performed */
69 };
70 .EE
71 .PP
72 For further information about this structure, see
73 .BR aio (7).
74 .PP
75 .IR "Conforming to" :
76 POSIX.1-2001 and later.
77 .PP
78 .IR "See also" :
79 .BR aio_cancel (3),
80 .BR aio_error (3),
81 .BR aio_fsync (3),
82 .BR aio_read (3),
83 .BR aio_return (3),
84 .BR aio_suspend (3),
85 .BR aio_write (3),
86 .BR lio_listio (3)
87 .RE
88 .\"------------------------------------- blkcnt_t ---------------------/
89 .TP
90 .I blkcnt_t
91 .RS
92 .IR Include :
93 .IR <sys/types.h> .
94 Alternatively,
95 .IR <sys/stat.h> .
96 .PP
97 Used for file block counts.
98 According to POSIX,
99 it shall be a signed integer type.
100 .PP
101 .IR "Conforming to" :
102 POSIX.1-2001 and later.
103 .PP
104 .IR "See also" :
105 .BR stat (2)
106 .RE
107 .\"------------------------------------- blksize_t --------------------/
108 .TP
109 .I blksize_t
110 .RS
111 .IR Include :
112 .IR <sys/types.h> .
113 Alternatively,
114 .IR <sys/stat.h> .
115 .PP
116 Used for file block sizes.
117 According to POSIX,
118 it shall be a signed integer type.
119 .PP
120 .IR "Conforming to" :
121 POSIX.1-2001 and later.
122 .PP
123 .IR "See also" :
124 .BR stat (2)
125 .RE
126 .\"------------------------------------- cc_t -------------------------/
127 .TP
128 .I cc_t
129 .RS
130 .IR Include :
131 .IR <termios.h> .
132 .PP
133 Used for terminal special characters.
134 According to POSIX,
135 it shall be an unsigned integer type.
136 .PP
137 .IR "Conforming to" :
138 POSIX.1-2001 and later.
139 .PP
140 .IR "See also" :
141 .BR termios (3)
142 .RE
143 .\"------------------------------------- clock_t ----------------------/
144 .TP
145 .I clock_t
146 .RS
147 .IR Include :
148 .I <time.h>
149 or
150 .IR <sys/types.h> .
151 Alternatively,
152 .IR <sys/time.h> .
153 .PP
154 Used for system time in clock ticks or
155 .B CLOCKS_PER_SEC
156 (defined in
157 .IR <time.h> ).
158 According to POSIX,
159 it shall be an integer type or a real-floating type.
160 .PP
161 .IR "Conforming to" :
162 C99 and later; POSIX.1-2001 and later.
163 .PP
164 .IR "See also" :
165 .BR times (2),
166 .BR clock (3)
167 .RE
168 .\"------------------------------------- clockid_t --------------------/
169 .TP
170 .I clockid_t
171 .RS
172 .IR Include :
173 .IR <sys/types.h> .
174 Alternatively,
175 .IR <time.h> .
176 .PP
177 Used for clock ID type in the clock and timer functions.
178 According to POSIX,
179 it shall be defined as an arithmetic type.
180 .PP
181 .IR "Conforming to" :
182 POSIX.1-2001 and later.
183 .PP
184 .IR "See also" :
185 .BR clock_adjtime (2),
186 .BR clock_getres (2),
187 .BR clock_nanosleep (2),
188 .BR timer_create (2),
189 .BR clock_getcpuclockid (3)
190 .RE
191 .\"------------------------------------- dev_t ------------------------/
192 .TP
193 .I dev_t
194 .RS
195 .IR Include :
196 .IR <sys/types.h> .
197 Alternatively,
198 .IR <sys/stat.h> .
199 .PP
200 Used for device IDs.
201 According to POSIX,
202 it shall be an integer type.
203 For further details of this type, see
204 .BR makedev (3).
205 .PP
206 .IR "Conforming to" :
207 POSIX.1-2001 and later.
208 .PP
209 .IR "See also" :
210 .BR mknod (2),
211 .BR stat (2)
212 .RE
213 .\"------------------------------------- div_t ------------------------/
214 .TP
215 .I div_t
216 .RS
217 .IR Include :
218 .IR <stdlib.h> .
219 .PP
220 .EX
221 typedef struct {
222 int quot; /* Quotient */
223 int rem; /* Remainder */
224 } div_t;
225 .EE
226 .PP
227 It is the type of the value returned by the
228 .BR div (3)
229 function.
230 .PP
231 .IR "Conforming to" :
232 C99 and later; POSIX.1-2001 and later.
233 .PP
234 .IR "See also" :
235 .BR div (3)
236 .RE
237 .\"------------------------------------- double_t ---------------------/
238 .TP
239 .I double_t
240 .RS
241 .IR Include :
242 .IR <math.h> .
243 .PP
244 The implementation's most efficient floating type at least as wide as
245 .IR double .
246 Its type depends on the value of the macro
247 .B FLT_EVAL_METHOD
248 (defined in
249 .IR <float.h> ):
250 .TP
251 0
252 .I double_t
253 is
254 .IR double .
255 .TP
256 1
257 .I double_t
258 is
259 .IR double .
260 .TP
261 2
262 .I double_t
263 is
264 .IR "long double" .
265 .PP
266 For other values of
267 .BR FLT_EVAL_METHOD ,
268 the type of
269 .I double_t
270 is implementation-defined.
271 .PP
272 .IR "Conforming to" :
273 C99 and later; POSIX.1-2001 and later.
274 .PP
275 .IR "See also" :
276 the
277 .I float_t
278 type in this page.
279 .RE
280 .\"------------------------------------- fd_set -----------------------/
281 .TP
282 .I fd_set
283 .RS
284 .IR Include :
285 .IR <sys/select.h> .
286 Alternatively,
287 .IR <sys/time.h> .
288 .PP
289 A structure type that can represent a set of file descriptors.
290 According to POSIX,
291 the maximum number of file descriptors in an
292 .I fd_set
293 structure is the value of the macro
294 .BR FD_SETSIZE .
295 .PP
296 .IR "Conforming to" :
297 POSIX.1-2001 and later.
298 .PP
299 .IR "See also" :
300 .BR select (2)
301 .RE
302 .\"------------------------------------- fenv_t -----------------------/
303 .TP
304 .I fenv_t
305 .RS
306 .IR Include :
307 .IR <fenv.h> .
308 .PP
309 This type represents the entire floating-point environment,
310 including control modes and status flags; for further details, see
311 .BR fenv (3).
312 .PP
313 .IR "Conforming to" :
314 C99 and later; POSIX.1-2001 and later.
315 .PP
316 .IR "See also" :
317 .BR fenv (3)
318 .RE
319 .\"------------------------------------- fexcept_t --------------------/
320 .TP
321 .I fexcept_t
322 .RS
323 .IR Include :
324 .IR <fenv.h> .
325 .PP
326 This type represents the floating-point status flags collectively;
327 for further details see
328 .BR fenv (3).
329 .PP
330 .IR "Conforming to" :
331 C99 and later; POSIX.1-2001 and later.
332 .PP
333 .IR "See also" :
334 .BR fenv (3)
335 .RE
336 .\"------------------------------------- FILE -------------------------/
337 .TP
338 .I FILE
339 .RS
340 .IR Include :
341 .IR <stdio.h> .
342 Alternatively,
343 .IR <wchar.h> .
344 .PP
345 An object type used for streams.
346 .PP
347 .IR "Conforming to" :
348 C99 and later; POSIX.1-2001 and later.
349 .PP
350 .IR "See also" :
351 .BR fclose (3),
352 .BR flockfile (3),
353 .BR fopen (3),
354 .BR fprintf (3),
355 .BR fread (3),
356 .BR fscanf (3),
357 .BR stdin (3),
358 .BR stdio (3)
359 .RE
360 .\"------------------------------------- float_t ----------------------/
361 .TP
362 .I float_t
363 .RS
364 .IR Include :
365 .IR <math.h> .
366 .PP
367 The implementation's most efficient floating type at least as wide as
368 .IR float .
369 Its type depends on the value of the macro
370 .B FLT_EVAL_METHOD
371 (defined in
372 .IR <float.h> ):
373 .TP
374 0
375 .I float_t
376 is
377 .IR float .
378 .TP
379 1
380 .I float_t
381 is
382 .IR double .
383 .TP
384 2
385 .I float_t
386 is
387 .IR "long double" .
388 .PP
389 For other values of
390 .BR FLT_EVAL_METHOD ,
391 the type of
392 .I float_t
393 is implementation-defined.
394 .PP
395 .IR "Conforming to" :
396 C99 and later; POSIX.1-2001 and later.
397 .PP
398 .IR "See also" :
399 the
400 .I double_t
401 type in this page.
402 .RE
403 .\"------------------------------------- gid_t ------------------------/
404 .TP
405 .I gid_t
406 .RS
407 .IR Include :
408 .IR <sys/types.h> .
409 Alternatively,
410 .IR <grp.h> ,
411 .IR <pwd.h> ,
412 .IR <signal.h> ,
413 .IR <stropts.h> ,
414 .IR <sys/ipc.h> ,
415 .IR <sys/stat.h> ,
416 or
417 .IR <unistd.h> .
418 .PP
419 A type used to hold group IDs.
420 According to POSIX,
421 this shall be an integer type.
422 .PP
423 .IR "Conforming to" :
424 POSIX.1-2001 and later.
425 .PP
426 .IR "See also" :
427 .BR chown (2),
428 .BR getgid (2),
429 .BR getegid (2),
430 .BR getgroups (2),
431 .BR getresgid (2),
432 .BR getgrnam (3),
433 .BR credentials (7)
434 .RE
435 .\"------------------------------------- id_t -------------------------/
436 .TP
437 .I id_t
438 .RS
439 .IR Include :
440 .IR <sys/types.h> .
441 Alternatively,
442 .IR <sys/resource.h> .
443 .PP
444 A type used to hold a general identifier.
445 According to POSIX,
446 this shall be an integer type that can be used to contain a
447 .IR pid_t ,
448 .IR uid_t ,
449 or
450 .IR gid_t .
451 .PP
452 .IR "Conforming to" :
453 POSIX.1-2001 and later.
454 .PP
455 .IR "See also" :
456 .BR getpriority (2),
457 .BR waitid (2)
458 .RE
459 .\"------------------------------------- imaxdiv_t --------------------/
460 .TP
461 .I imaxdiv_t
462 .RS
463 .IR Include :
464 .IR <inttypes.h> .
465 .PP
466 .EX
467 typedef struct {
468 intmax_t quot; /* Quotient */
469 intmax_t rem; /* Remainder */
470 } imaxdiv_t;
471 .EE
472 .PP
473 It is the type of the value returned by the
474 .BR imaxdiv (3)
475 function.
476 .PP
477 .IR "Conforming to" :
478 C99 and later; POSIX.1-2001 and later.
479 .PP
480 .IR "See also" :
481 .BR imaxdiv (3)
482 .RE
483 .\"------------------------------------- intmax_t ---------------------/
484 .TP
485 .I intmax_t
486 .RS
487 .IR Include :
488 .IR <stdint.h> .
489 Alternatively,
490 .IR <inttypes.h> .
491 .PP
492 A signed integer type
493 capable of representing any value of any signed integer type
494 supported by the implementation.
495 According to the C language standard, it shall be
496 capable of storing values in the range
497 .RB [ INTMAX_MIN ,
498 .BR INTMAX_MAX ].
499 .PP
500 The macro
501 .BR INTMAX_C ()
502 .\" TODO: Document INT*_C(3)
503 expands its argument to an integer constant of type
504 .IR intmax_t .
505 .PP
506 The length modifier for
507 .I intmax_t
508 for the
509 .BR printf (3)
510 and the
511 .BR scanf (3)
512 families of functions is
513 .BR j ;
514 resulting commonly in
515 .B %jd
516 or
517 .B %ji
518 for printing
519 .I intmax_t
520 values.
521 .PP
522 .IR "Conforming to" :
523 C99 and later; POSIX.1-2001 and later.
524 .PP
525 .IR Bugs :
526 .I intmax_t
527 is not large enough to represent values of type
528 .I __int128
529 in implementations where
530 .I __int128
531 is defined and
532 .I long long
533 is less than 128 bits wide.
534 .PP
535 .IR "See also" :
536 the
537 .I uintmax_t
538 type in this page.
539 .RE
540 .\"------------------------------------- intN_t -----------------------/
541 .TP
542 .IR int N _t
543 .RS
544 .IR Include :
545 .IR <stdint.h> .
546 Alternatively,
547 .IR <inttypes.h> .
548 .PP
549 .IR int8_t ,
550 .IR int16_t ,
551 .IR int32_t ,
552 .I int64_t
553 .PP
554 A signed integer type
555 of a fixed width of exactly N bits,
556 N being the value specified in its type name.
557 According to the C language standard, they shall be
558 capable of storing values in the range
559 .RB [ INT N _MIN ,
560 .BR INT N _MAX ],
561 substituting N by the appropriate number.
562 .PP
563 According to POSIX,
564 .IR int8_t ,
565 .IR int16_t ,
566 and
567 .I int32_t
568 are required;
569 .I int64_t
570 is only required in implementations that provide integer types
571 with width 64;
572 and all other types of this form are optional.
573 .PP
574 The length modifiers for the
575 .IR int N _t
576 types for the
577 .BR printf (3)
578 family of functions
579 are expanded by macros of the forms
580 .BR PRId N
581 and
582 .BR PRIi N
583 (defined in
584 .IR <inttypes.h> );
585 resulting for example in
586 .B %"PRId64"
587 or
588 .B %"PRIi64"
589 for printing
590 .I int64_t
591 values.
592 The length modifiers for the
593 .IR int N _t
594 types for the
595 .BR scanf (3)
596 family of functions
597 are expanded by macros of the forms
598 .BR SCNd N
599 and
600 .BR SCNi N,
601 (defined in
602 .IR <inttypes.h> );
603 resulting for example in
604 .B %"SCNd8"
605 or
606 .B %"SCNi8"
607 for scanning
608 .I int8_t
609 values.
610 .PP
611 .IR "Conforming to" :
612 C99 and later; POSIX.1-2001 and later.
613 .PP
614 .IR "See also" :
615 the
616 .IR intmax_t ,
617 .IR uint N _t ,
618 and
619 .I uintmax_t
620 types in this page.
621 .RE
622 .\"------------------------------------- intptr_t ---------------------/
623 .TP
624 .I intptr_t
625 .RS
626 .IR Include :
627 .IR <stdint.h> .
628 Alternatively,
629 .IR <inttypes.h> .
630 .PP
631 A signed integer type
632 such that any valid
633 .RI ( "void *" )
634 value can be converted to this type and back.
635 According to the C language standard, it shall be
636 capable of storing values in the range
637 .RB [ INTPTR_MIN ,
638 .BR INTPTR_MAX ].
639 .PP
640 The length modifier for
641 .I intptr_t
642 for the
643 .BR printf (3)
644 family of functions
645 is expanded by the macros
646 .B PRIdPTR
647 and
648 .B PRIiPTR
649 (defined in
650 .IR <inttypes.h> );
651 resulting commonly in
652 .B %"PRIdPTR"
653 or
654 .B %"PRIiPTR"
655 for printing
656 .I intptr_t
657 values.
658 The length modifier for
659 .I intptr_t
660 for the
661 .BR scanf (3)
662 family of functions
663 is expanded by the macros
664 .B SCNdPTR
665 and
666 .B SCNiPTR,
667 (defined in
668 .IR <inttypes.h> );
669 resulting commonly in
670 .B %"SCNdPTR"
671 or
672 .B %"SCNiPTR"
673 for scanning
674 .I intptr_t
675 values.
676 .PP
677 .IR "Conforming to" :
678 C99 and later; POSIX.1-2001 and later.
679 .PP
680 .IR "See also" :
681 the
682 .I uintptr_t
683 and
684 .I void *
685 types in this page.
686 .RE
687 .\"------------------------------------- lconv ------------------------/
688 .TP
689 .I lconv
690 .RS
691 .IR Include :
692 .IR <locale.h> .
693 .PP
694 .EX
695 struct lconv { /* Values in the "C" locale: */
696 char *decimal_point; /* "." */
697 char *thousands_sep; /* "" */
698 char *grouping; /* "" */
699 char *mon_decimal_point; /* "" */
700 char *mon_thousands_sep; /* "" */
701 char *mon_grouping; /* "" */
702 char *positive_sign; /* "" */
703 char *negative_sign; /* "" */
704 char *currency_symbol; /* "" */
705 char frac_digits; /* CHAR_MAX */
706 char p_cs_precedes; /* CHAR_MAX */
707 char n_cs_precedes; /* CHAR_MAX */
708 char p_sep_by_space; /* CHAR_MAX */
709 char n_sep_by_space; /* CHAR_MAX */
710 char p_sign_posn; /* CHAR_MAX */
711 char n_sign_posn; /* CHAR_MAX */
712 char *int_curr_symbol; /* "" */
713 char int_frac_digits; /* CHAR_MAX */
714 char int_p_cs_precedes; /* CHAR_MAX */
715 char int_n_cs_precedes; /* CHAR_MAX */
716 char int_p_sep_by_space; /* CHAR_MAX */
717 char int_n_sep_by_space; /* CHAR_MAX */
718 char int_p_sign_posn; /* CHAR_MAX */
719 char int_n_sign_posn; /* CHAR_MAX */
720 };
721 .EE
722 .PP
723 Contains members related to the formatting of numeric values.
724 In the "C" locale, its members have the values
725 shown in the comments above.
726 .PP
727 .IR "Conforming to" :
728 C11 and later; POSIX.1-2001 and later.
729 .PP
730 .IR "See also" :
731 .BR setlocale (3),
732 .BR localeconv (3),
733 .BR charsets (7),
734 .BR locale (7)
735 .RE
736 .\"------------------------------------- ldiv_t -----------------------/
737 .TP
738 .I ldiv_t
739 .RS
740 .IR Include :
741 .IR <stdlib.h> .
742 .PP
743 .EX
744 typedef struct {
745 long quot; /* Quotient */
746 long rem; /* Remainder */
747 } ldiv_t;
748 .EE
749 .PP
750 It is the type of the value returned by the
751 .BR ldiv (3)
752 function.
753 .PP
754 .IR "Conforming to" :
755 C99 and later; POSIX.1-2001 and later.
756 .PP
757 .IR "See also" :
758 .BR ldiv (3)
759 .RE
760 .\"------------------------------------- lldiv_t ----------------------/
761 .TP
762 .I lldiv_t
763 .RS
764 .IR Include :
765 .IR <stdlib.h> .
766 .PP
767 .EX
768 typedef struct {
769 long long quot; /* Quotient */
770 long long rem; /* Remainder */
771 } lldiv_t;
772 .EE
773 .PP
774 It is the type of the value returned by the
775 .BR lldiv (3)
776 function.
777 .PP
778 .IR "Conforming to" :
779 C99 and later; POSIX.1-2001 and later.
780 .PP
781 .IR "See also" :
782 .BR lldiv (3)
783 .RE
784 .\"------------------------------------- mode_t -----------------------/
785 .TP
786 .I mode_t
787 .RS
788 .IR Include :
789 .IR <sys/types.h> .
790 Alternatively,
791 .IR <fcntl.h> ,
792 .IR <ndbm.h> ,
793 .IR <spawn.h> ,
794 .IR <sys/ipc.h> ,
795 .IR <sys/mman.h> ,
796 or
797 .IR <sys/stat.h> .
798 .PP
799 Used for some file attributes (e.g., file mode).
800 According to POSIX,
801 it shall be an integer type.
802 .PP
803 .IR "Conforming to" :
804 POSIX.1-2001 and later.
805 .PP
806 .IR "See also" :
807 .BR chmod (2),
808 .BR mkdir (2),
809 .BR open (2),
810 .BR stat (2),
811 .BR umask (2)
812 .RE
813 .\"------------------------------------- off64_t ----------------------/
814 .TP
815 .I off64_t
816 .RS
817 .IR Include :
818 .IR <sys/types.h> .
819 .PP
820 Used for file sizes.
821 It is a 64-bit signed integer type.
822 .PP
823 .IR "Conforming to" :
824 Present in glibc.
825 It is not standardized by the C language standard nor POSIX.
826 .PP
827 .IR Notes :
828 The feature test macro
829 .B _LARGEFILE64_SOURCE
830 has to be defined for this type to be available.
831 .PP
832 .IR "See also" :
833 .BR copy_file_range (2),
834 .BR readahead (2),
835 .BR sync_file_range (2),
836 .BR lseek64 (3),
837 .BR feature_test_macros (7)
838 .PP
839 See also the
840 .\" .I loff_t
841 .\" and
842 .I off_t
843 type in this page.
844 .RE
845 .\"------------------------------------- off_t ------------------------/
846 .TP
847 .I off_t
848 .RS
849 .IR Include :
850 .IR <sys/types.h> .
851 Alternatively,
852 .IR <aio.h> ,
853 .IR <fcntl.h> ,
854 .IR <stdio.h> ,
855 .IR <sys/mman.h> ,
856 .IR <sys/stat.h.h> ,
857 or
858 .IR <unistd.h> .
859 .PP
860 Used for file sizes.
861 According to POSIX,
862 this shall be a signed integer type.
863 .PP
864 .IR Versions :
865 .I <aio.h>
866 and
867 .I <stdio.h>
868 define
869 .I off_t
870 since POSIX.1-2008.
871 .PP
872 .IR "Conforming to" :
873 POSIX.1-2001 and later.
874 .PP
875 .IR Notes :
876 On some architectures,
877 the width of this type can be controlled with the feature test macro
878 .BR _FILE_OFFSET_BITS .
879 .PP
880 .IR "See also" :
881 .\" .BR fallocate (2),
882 .BR lseek (2),
883 .BR mmap (2),
884 .\" .BR mmap2 (2),
885 .BR posix_fadvise (2),
886 .BR pread (2),
887 .\" .BR preadv (2),
888 .BR truncate (2),
889 .BR fseeko (3),
890 .\" .BR getdirentries (3),
891 .BR lockf (3),
892 .BR posix_fallocate (3),
893 .BR feature_test_macros (7)
894 .PP
895 See also the
896 .\" .I loff_t
897 .\" and
898 .I off64_t
899 type in this page.
900 .RE
901 .\"------------------------------------- pid_t ------------------------/
902 .TP
903 .I pid_t
904 .RS
905 .IR Include :
906 .IR <sys/types.h> .
907 Alternatively,
908 .IR <fcntl.h> ,
909 .IR <sched.h> ,
910 .IR <signal.h> ,
911 .IR <spawn.h> ,
912 .IR <sys/msg.h> ,
913 .IR <sys/sem.h> ,
914 .IR <sys/shm.h> ,
915 .IR <sys/wait.h> ,
916 .IR <termios.h> ,
917 .IR <time.h> ,
918 .IR <unistd.h> ,
919 or
920 .IR <utmpx.h> .
921 .PP
922 This type is used for storing process IDs, process group IDs, and session IDs.
923 According to POSIX, it shall be a signed integer type,
924 and the implementation shall support one or more programming environments
925 where the width of
926 .I pid_t
927 is no greater than the width of the type
928 .IR long .
929 .PP
930 .IR "Conforming to" :
931 POSIX.1-2001 and later.
932 .PP
933 .IR "See also" :
934 .BR fork (2),
935 .BR getpid (2),
936 .BR getppid (2),
937 .BR getsid (2),
938 .BR gettid (2),
939 .BR getpgid (2),
940 .BR kill (2),
941 .BR pidfd_open (2),
942 .BR sched_setscheduler (2),
943 .BR waitpid (2),
944 .BR sigqueue (3),
945 .BR credentials (7),
946 .RE
947 .\"------------------------------------- ptrdiff_t --------------------/
948 .TP
949 .I ptrdiff_t
950 .RS
951 .IR Include :
952 .IR <stddef.h> .
953 .PP
954 Used for a count of elements, and array indices.
955 It is the result of subtracting two pointers.
956 According to the C language standard, it shall be a signed integer type
957 capable of storing values in the range
958 .RB [ PTRDIFF_MIN ,
959 .BR PTRDIFF_MAX ].
960 .PP
961 The length modifier for
962 .I ptrdiff_t
963 for the
964 .BR printf (3)
965 and the
966 .BR scanf (3)
967 families of functions is
968 .BR t ;
969 resulting commonly in
970 .B %td
971 or
972 .B %ti
973 for printing
974 .I ptrdiff_t
975 values.
976 .PP
977 .IR "Conforming to" :
978 C99 and later; POSIX.1-2001 and later.
979 .PP
980 .IR "See also" :
981 the
982 .I size_t
983 and
984 .I ssize_t
985 types in this page.
986 .RE
987 .\"------------------------------------- regex_t ----------------------/
988 .TP
989 .I regex_t
990 .RS
991 .IR Include :
992 .IR <regex.h> .
993 .PP
994 .EX
995 typedef struct {
996 size_t re_nsub; /* Number of parenthesized subexpressions */
997 } regex_t;
998 .EE
999 .PP
1000 This is a structure type used in regular expression matching.
1001 It holds a compiled regular expression, compiled with
1002 .BR regcomp (3).
1003 .PP
1004 .IR "Conforming to" :
1005 POSIX.1-2001 and later.
1006 .PP
1007 .IR "See also" :
1008 .BR regex (3)
1009 .RE
1010 .\"------------------------------------- regmatch_t -------------------/
1011 .TP
1012 .I regmatch_t
1013 .RS
1014 .IR Include :
1015 .IR <regex.h> .
1016 .PP
1017 .EX
1018 typedef struct {
1019 regoff_t rm_so; /* Byte offset from start of string
1020 to start of substring */
1021 regoff_t rm_eo; /* Byte offset from start of string of
1022 the first character after the end of
1023 substring */
1024 } regmatch_t;
1025 .EE
1026 .PP
1027 This is a structure type used in regular expression matching.
1028 .PP
1029 .IR "Conforming to" :
1030 POSIX.1-2001 and later.
1031 .PP
1032 .IR "See also" :
1033 .BR regexec (3)
1034 .RE
1035 .\"------------------------------------- regoff_t ---------------------/
1036 .TP
1037 .I regoff_t
1038 .RS
1039 .IR Include :
1040 .IR <regex.h> .
1041 .PP
1042 According to POSIX, it shall be a signed integer type
1043 capable of storing the largest value that can be stored in either a
1044 .I ptrdiff_t
1045 type or a
1046 .I ssize_t
1047 type.
1048 .PP
1049 .IR Versions :
1050 Prior to POSIX.1-2008, the type was capable of storing
1051 the largest value that can be stored in either an
1052 .I off_t
1053 type or a
1054 .I ssize_t
1055 type.
1056 .PP
1057 .IR "Conforming to" :
1058 POSIX.1-2001 and later.
1059 .PP
1060 .IR "See also" :
1061 the
1062 .I regmatch_t
1063 structure and the
1064 .I ptrdiff_t
1065 and
1066 .I ssize_t
1067 types in this page.
1068 .RE
1069 .\"------------------------------------- sigevent ---------------------/
1070 .TP
1071 .I sigevent
1072 .RS
1073 .IR Include :
1074 .IR <signal.h> .
1075 Alternatively,
1076 .IR <aio.h> ,
1077 .IR <mqueue.h> ,
1078 or
1079 .IR <time.h> .
1080 .PP
1081 .EX
1082 struct sigevent {
1083 int sigev_notify; /* Notification type */
1084 int sigev_signo; /* Signal number */
1085 union sigval sigev_value; /* Signal value */
1086 void (*sigev_notify_function)(union sigval);
1087 /* Notification function */
1088 pthread_attr_t *sigev_notify_attributes;
1089 /* Notification attributes */
1090 };
1091 .EE
1092 .PP
1093 For further details about this type, see
1094 .BR sigevent (7).
1095 .PP
1096 .IR Versions :
1097 .I <aio.h>
1098 and
1099 .I <time.h>
1100 define
1101 .I sigevent
1102 since POSIX.1-2008.
1103 .PP
1104 .IR "Conforming to" :
1105 POSIX.1-2001 and later.
1106 .PP
1107 .IR "See also" :
1108 .BR timer_create (2),
1109 .BR getaddrinfo_a (3),
1110 .BR lio_listio (3),
1111 .BR mq_notify (3)
1112 .PP
1113 See also the
1114 .I aiocb
1115 structure in this page.
1116 .RE
1117 .\"------------------------------------- siginfo_t --------------------/
1118 .TP
1119 .I siginfo_t
1120 .RS
1121 .IR Include :
1122 .IR <signal.h> .
1123 Alternatively,
1124 .IR <sys/wait.h> .
1125 .PP
1126 .EX
1127 typedef struct {
1128 int si_signo; /* Signal number */
1129 int si_code; /* Signal code */
1130 pid_t si_pid; /* Sending process ID */
1131 uid_t si_uid; /* Real user ID of sending process */
1132 void *si_addr; /* Address of faulting instruction */
1133 int si_status; /* Exit value or signal */
1134 union sigval si_value; /* Signal value */
1135 } siginfo_t;
1136 .EE
1137 .PP
1138 Information associated with a signal.
1139 For further details on this structure
1140 (including additional, Linux-specific fields), see
1141 .BR sigaction (2).
1142 .PP
1143 .IR "Conforming to" :
1144 POSIX.1-2001 and later.
1145 .PP
1146 .IR "See also" :
1147 .BR pidfd_send_signal (2),
1148 .BR rt_sigqueueinfo (2),
1149 .BR sigaction (2),
1150 .BR sigwaitinfo (2),
1151 .BR psiginfo (3)
1152 .RE
1153 .\"------------------------------------- sigset_t ---------------------/
1154 .TP
1155 .I sigset_t
1156 .RS
1157 .IR Include :
1158 .IR <signal.h> .
1159 Alternatively,
1160 .IR <spawn.h> ,
1161 or
1162 .IR <sys/select.h> .
1163 .PP
1164 This is a type that represents a set of signals.
1165 According to POSIX, this shall be an integer or structure type.
1166 .PP
1167 .IR "Conforming to" :
1168 POSIX.1-2001 and later.
1169 .PP
1170 .IR "See also" :
1171 .BR epoll_pwait (2),
1172 .BR ppoll (2),
1173 .BR pselect (2),
1174 .BR sigaction (2),
1175 .BR signalfd (2),
1176 .BR sigpending (2),
1177 .BR sigprocmask (2),
1178 .BR sigsuspend (2),
1179 .BR sigwaitinfo (2),
1180 .BR signal (7)
1181 .RE
1182 .\"------------------------------------- sigval -----------------------/
1183 .TP
1184 .I sigval
1185 .RS
1186 .IR Include :
1187 .IR <signal.h> .
1188 .PP
1189 .EX
1190 union sigval {
1191 int sigval_int; /* Integer value */
1192 void *sigval_ptr; /* Pointer value */
1193 };
1194 .EE
1195 .PP
1196 Data passed with a signal.
1197 .PP
1198 .IR "Conforming to" :
1199 POSIX.1-2001 and later.
1200 .PP
1201 .IR "See also" :
1202 .BR pthread_sigqueue (3),
1203 .BR sigqueue (3),
1204 .BR sigevent (7)
1205 .PP
1206 See also the
1207 .I sigevent
1208 structure
1209 and the
1210 .I siginfo_t
1211 type
1212 in this page.
1213 .RE
1214 .\"------------------------------------- size_t -----------------------/
1215 .TP
1216 .I size_t
1217 .RS
1218 .IR Include :
1219 .I <stddef.h>
1220 or
1221 .IR <sys/types.h> .
1222 Alternatively,
1223 .IR <aio.h> ,
1224 .IR <glob.h> ,
1225 .IR <grp.h> ,
1226 .IR <iconv.h> ,
1227 .IR <monetary.h> ,
1228 .IR <mqueue.h> ,
1229 .IR <ndbm.h> ,
1230 .IR <pwd.h> ,
1231 .IR <regex.h> ,
1232 .IR <search.h> ,
1233 .IR <signal.h> ,
1234 .IR <stdio.h> ,
1235 .IR <stdlib.h> ,
1236 .IR <string.h> ,
1237 .IR <strings.h> ,
1238 .IR <sys/mman.h> ,
1239 .IR <sys/msg.h> ,
1240 .IR <sys/sem.h> ,
1241 .IR <sys/shm.h> ,
1242 .IR <sys/socket.h> ,
1243 .IR <sys/uio.h> ,
1244 .IR <time.h> ,
1245 .IR <unistd.h> ,
1246 .IR <wchar.h> ,
1247 or
1248 .IR <wordexp.h> .
1249 .PP
1250 Used for a count of bytes. It is the result of the
1251 .I sizeof
1252 operator.
1253 According to the C language standard,
1254 it shall be an unsigned integer type
1255 capable of storing values in the range [0,
1256 .BR SIZE_MAX ].
1257 According to POSIX,
1258 the implementation shall support one or more programming environments
1259 where the width of
1260 .I size_t
1261 is no greater than the width of the type
1262 .IR long .
1263 .PP
1264 The length modifier for
1265 .I size_t
1266 for the
1267 .BR printf (3)
1268 and the
1269 .BR scanf (3)
1270 families of functions is
1271 .BR z ;
1272 resulting commonly in
1273 .B %zu
1274 or
1275 .B %zx
1276 for printing
1277 .I size_t
1278 values.
1279 .PP
1280 .IR Versions :
1281 .IR <aio.h> ,
1282 .IR <glob.h> ,
1283 .IR <grp.h> ,
1284 .IR <iconv.h> ,
1285 .IR <mqueue.h> ,
1286 .IR <pwd.h> ,
1287 .IR <signal.h> ,
1288 and
1289 .I <sys/socket.h>
1290 define
1291 .I size_t
1292 since POSIX.1-2008.
1293 .PP
1294 .IR "Conforming to" :
1295 C99 and later; POSIX.1-2001 and later.
1296 .PP
1297 .IR "See also" :
1298 .BR read (2),
1299 .BR write (2),
1300 .BR fread (3),
1301 .BR fwrite (3),
1302 .BR memcmp (3),
1303 .BR memcpy (3),
1304 .BR memset (3),
1305 .BR offsetof (3)
1306 .PP
1307 See also the
1308 .I ptrdiff_t
1309 and
1310 .I ssize_t
1311 types in this page.
1312 .RE
1313 .\"------------------------------------- sockaddr ---------------------/
1314 .TP
1315 .I sockaddr
1316 .RS
1317 .IR Include :
1318 .IR <sys/socket.h> .
1319 .PP
1320 .EX
1321 struct sockaddr {
1322 sa_family_t sa_family; /* Address family */
1323 char sa_data[]; /* Socket address */
1324 };
1325 .EE
1326 .PP
1327 Describes a socket address.
1328 .PP
1329 .IR "Conforming to" :
1330 POSIX.1-2001 and later.
1331 .PP
1332 .IR "See also" :
1333 .BR accept (2),
1334 .BR getpeername (2),
1335 .BR getsockname (2),
1336 .BR socket (2)
1337 .RE
1338 .\"------------------------------------- socklen_t --------------------/
1339 .TP
1340 .I socklen_t
1341 .RS
1342 .IR Include :
1343 .IR <sys/socket.h> .
1344 Alternatively,
1345 .IR <netdb.h> .
1346 .PP
1347 Describes the length of a socket address.
1348 According to POSIX,
1349 this shall be an integer type of at least 32 bits.
1350 .PP
1351 .IR "Conforming to" :
1352 POSIX.1-2001 and later.
1353 .PP
1354 .IR "See also" :
1355 .BR accept (2),
1356 .BR bind (2),
1357 .BR connect (2),
1358 .BR gethostbyaddr (2),
1359 .BR getnameinfo (2),
1360 .BR socket (2)
1361 .PP
1362 See also the
1363 .I sockaddr
1364 structure in this page.
1365 .RE
1366 .\"------------------------------------- ssize_t ----------------------/
1367 .TP
1368 .I ssize_t
1369 .RS
1370 .IR Include :
1371 .IR <sys/types.h> .
1372 Alternatively,
1373 .IR <aio.h> ,
1374 .IR <monetary.h> ,
1375 .IR <mqueue.h> ,
1376 .IR <stdio.h> ,
1377 .IR <sys/msg.h> ,
1378 .IR <sys/socket.h> ,
1379 .IR <sys/uio.h> ,
1380 or
1381 .IR <unistd.h> .
1382 .PP
1383 Used for a count of bytes or an error indication.
1384 According to POSIX, it shall be a signed integer type
1385 capable of storing values at least in the range [-1,
1386 .BR SSIZE_MAX ],
1387 and the implementation shall support one or more programming environments
1388 where the width of
1389 .I ssize_t
1390 is no greater than the width of the type
1391 .IR long .
1392 .PP
1393 Glibc and most other implementations provide a length modifier for
1394 .I ssize_t
1395 for the
1396 .BR printf (3)
1397 and the
1398 .BR scanf (3)
1399 families of functions, which is
1400 .BR z ;
1401 resulting commonly in
1402 .B %zd
1403 or
1404 .B %zi
1405 for printing
1406 .I ssize_t
1407 values.
1408 Although
1409 .B z
1410 works for
1411 .I ssize_t
1412 on most implementations,
1413 portable POSIX programs should avoid using it\(emfor example,
1414 by converting the value to
1415 .I intmax_t
1416 and using its length modifier
1417 .RB ( j ).
1418 .PP
1419 .IR "Conforming to" :
1420 POSIX.1-2001 and later.
1421 .PP
1422 .IR "See also" :
1423 .BR read (2),
1424 .BR readlink (2),
1425 .BR readv (2),
1426 .BR recv (2),
1427 .BR send (2),
1428 .BR write (2)
1429 .PP
1430 See also the
1431 .I ptrdiff_t
1432 and
1433 .I size_t
1434 types in this page.
1435 .RE
1436 .\"------------------------------------- suseconds_t ------------------/
1437 .TP
1438 .I suseconds_t
1439 .RS
1440 .IR Include :
1441 .IR <sys/types.h> .
1442 Alternatively,
1443 .IR <sys/select.h> ,
1444 or
1445 .IR <sys/time.h> .
1446 .PP
1447 Used for time in microseconds.
1448 According to POSIX, it shall be a signed integer type
1449 capable of storing values at least in the range [-1, 1000000],
1450 and the implementation shall support one or more programming environments
1451 where the width of
1452 .I suseconds_t
1453 is no greater than the width of the type
1454 .IR long .
1455 .PP
1456 .IR "Conforming to" :
1457 POSIX.1-2001 and later.
1458 .PP
1459 .IR "See also" :
1460 the
1461 .I timeval
1462 structure in this page.
1463 .RE
1464 .\"------------------------------------- time_t -----------------------/
1465 .TP
1466 .I time_t
1467 .RS
1468 .IR Include :
1469 .I <time.h>
1470 or
1471 .IR <sys/types.h> .
1472 Alternatively,
1473 .IR <sched.h> ,
1474 .IR <sys/msg.h> ,
1475 .IR <sys/select.h> ,
1476 .IR <sys/sem.h> ,
1477 .IR <sys/shm.h> ,
1478 .IR <sys/stat.h> ,
1479 .IR <sys/time.h> ,
1480 or
1481 .IR <utime.h> .
1482 .PP
1483 Used for time in seconds.
1484 According to POSIX, it shall be an integer type.
1485 .\" In POSIX.1-2001, the type was specified as being either an integer
1486 .\" type or a real-floating type. However, existing implementations
1487 .\" used an integer type, and POSIX.1-2008 tightened the specification
1488 .\" to reflect this.
1489 .PP
1490 .IR Versions :
1491 .I <sched.h>
1492 defines
1493 .I time_t
1494 since POSIX.1-2008.
1495 .PP
1496 .IR "Conforming to" :
1497 C99 and later; POSIX.1-2001 and later.
1498 .PP
1499 .IR "See also" :
1500 .BR stime (2),
1501 .BR time (2),
1502 .BR ctime (3),
1503 .BR difftime (3)
1504 .RE
1505 .\"------------------------------------- timer_t ----------------------/
1506 .TP
1507 .I timer_t
1508 .RS
1509 .IR Include :
1510 .IR <sys/types.h> .
1511 Alternatively,
1512 .IR <time.h> .
1513 .PP
1514 Used for timer ID returned by
1515 .BR timer_create (2).
1516 According to POSIX,
1517 there are no defined comparison or assignment operators for this type.
1518 .PP
1519 .IR "Conforming to" :
1520 POSIX.1-2001 and later.
1521 .PP
1522 .IR "See also" :
1523 .BR timer_create (2),
1524 .BR timer_delete (2),
1525 .BR timer_getoverrun (2),
1526 .BR timer_settime (2)
1527 .RE
1528 .\"------------------------------------- timespec ---------------------/
1529 .TP
1530 .I timespec
1531 .RS
1532 .IR Include :
1533 .IR <time.h> .
1534 Alternatively,
1535 .IR <aio.h> ,
1536 .IR <mqueue.h> ,
1537 .IR <sched.h> ,
1538 .IR <signal.h> ,
1539 .IR <sys/select.h> ,
1540 or
1541 .IR <sys/stat.h> .
1542 .PP
1543 .EX
1544 struct timespec {
1545 time_t tv_sec; /* Seconds */
1546 long tv_nsec; /* Nanoseconds */
1547 };
1548 .EE
1549 .PP
1550 Describes times in seconds and nanoseconds.
1551 .PP
1552 .IR "Conforming to" :
1553 C11 and later; POSIX.1-2001 and later.
1554 .PP
1555 .IR "See also" :
1556 .BR clock_gettime (2),
1557 .BR clock_nanosleep (2),
1558 .BR nanosleep (2),
1559 .BR timerfd_gettime (2),
1560 .BR timer_gettime (2)
1561 .RE
1562 .\"------------------------------------- timeval ----------------------/
1563 .TP
1564 .I timeval
1565 .RS
1566 .IR Include :
1567 .IR <sys/time.h> .
1568 Alternatively,
1569 .IR <sys/resource.h> ,
1570 .IR <sys/select.h> ,
1571 or
1572 .IR <utmpx.h> .
1573 .PP
1574 .EX
1575 struct timeval {
1576 time_t tv_sec; /* Seconds */
1577 suseconds_t tv_usec; /* Microseconds */
1578 };
1579 .EE
1580 .PP
1581 Describes times in seconds and microseconds.
1582 .PP
1583 .IR "Conforming to" :
1584 POSIX.1-2001 and later.
1585 .PP
1586 .IR "See also" :
1587 .BR gettimeofday (2),
1588 .BR select (2),
1589 .BR utimes (2),
1590 .BR adjtime (3),
1591 .BR futimes (3),
1592 .BR timeradd (3)
1593 .RE
1594 .\"------------------------------------- uid_t ----------------------/
1595 .TP
1596 .I uid_t
1597 .RS
1598 .IR Include :
1599 .IR <sys/types.h> .
1600 Alternatively,
1601 .IR <pwd.h> ,
1602 .IR <signal.h> ,
1603 .IR <stropts.h> ,
1604 .IR <sys/ipc.h> ,
1605 .IR <sys/stat.h> ,
1606 or
1607 .IR <unistd.h> .
1608 .PP
1609 A type used to hold user IDs.
1610 According to POSIX,
1611 this shall be an integer type.
1612 .PP
1613 .IR "Conforming to" :
1614 POSIX.1-2001 and later.
1615 .PP
1616 .IR "See also" :
1617 .BR chown (2),
1618 .BR getuid (2),
1619 .BR geteuid (2),
1620 .BR getresuid (2),
1621 .BR getpwnam (3),
1622 .BR credentials (7)
1623 .RE
1624 .\"------------------------------------- uintmax_t --------------------/
1625 .TP
1626 .I uintmax_t
1627 .RS
1628 .IR Include :
1629 .IR <stdint.h> .
1630 Alternatively,
1631 .IR <inttypes.h> .
1632 .PP
1633 An unsigned integer type
1634 capable of representing any value of any unsigned integer type
1635 supported by the implementation.
1636 According to the C language standard, it shall be
1637 capable of storing values in the range [0,
1638 .BR UINTMAX_MAX ].
1639 .PP
1640 The macro
1641 .BR UINTMAX_C ()
1642 .\" TODO: Document UINT*_C(3)
1643 expands its argument to an integer constant of type
1644 .IR uintmax_t .
1645 .PP
1646 The length modifier for
1647 .I uintmax_t
1648 for the
1649 .BR printf (3)
1650 and the
1651 .BR scanf (3)
1652 families of functions is
1653 .BR j ;
1654 resulting commonly in
1655 .B %ju
1656 or
1657 .B %jx
1658 for printing
1659 .I uintmax_t
1660 values.
1661 .PP
1662 .IR "Conforming to" :
1663 C99 and later; POSIX.1-2001 and later.
1664 .PP
1665 .IR Bugs :
1666 .I uintmax_t
1667 is not large enough to represent values of type
1668 .I unsigned __int128
1669 in implementations where
1670 .I unsigned __int128
1671 is defined and
1672 .I unsigned long long
1673 is less than 128 bits wide.
1674 .PP
1675 .IR "See also" :
1676 the
1677 .I intmax_t
1678 type in this page.
1679 .RE
1680 .\"------------------------------------- uintN_t ----------------------/
1681 .TP
1682 .IR uint N _t
1683 .RS
1684 .IR Include :
1685 .IR <stdint.h> .
1686 Alternatively,
1687 .IR <inttypes.h> .
1688 .PP
1689 .IR uint8_t ,
1690 .IR uint16_t ,
1691 .IR uint32_t ,
1692 .I uint64_t
1693 .PP
1694 An unsigned integer type
1695 of a fixed width of exactly N bits,
1696 N being the value specified in its type name.
1697 According to the C language standard, they shall be
1698 capable of storing values in the range [0,
1699 .BR UINT N _MAX ],
1700 substituting N by the appropriate number.
1701 .PP
1702 According to POSIX,
1703 .IR uint8_t ,
1704 .IR uint16_t ,
1705 and
1706 .I uint32_t
1707 are required;
1708 .I uint64_t
1709 is only required in implementations that provide integer types
1710 with width 64;
1711 and all other types of this form are optional.
1712 .PP
1713 The length modifiers for the
1714 .IR uint N _t
1715 types for the
1716 .BR printf (3)
1717 family of functions
1718 are expanded by macros of the forms
1719 .BR PRIu N,
1720 .BR PRIo N,
1721 .BR PRIx N,
1722 and
1723 .BR PRIX N
1724 (defined in
1725 .IR <inttypes.h> );
1726 resulting for example in
1727 .B %"PRIu32"
1728 or
1729 .B %"PRIx32"
1730 for printing
1731 .I uint32_t
1732 values.
1733 The length modifiers for the
1734 .IR uint N _t
1735 types for the
1736 .BR scanf (3)
1737 family of functions
1738 are expanded by macros of the forms
1739 .BR SCNu N,
1740 .BR SCNo N,
1741 .BR SCNx N,
1742 and
1743 .BR SCNX N
1744 (defined in
1745 .IR <inttypes.h> );
1746 resulting for example in
1747 .B %"SCNu16"
1748 or
1749 .B %"SCNx16"
1750 for scanning
1751 .I uint16_t
1752 values.
1753 .PP
1754 .IR "Conforming to" :
1755 C99 and later; POSIX.1-2001 and later.
1756 .PP
1757 .IR "See also" :
1758 the
1759 .IR intmax_t ,
1760 .IR int N _t ,
1761 and
1762 .IR uintmax_t
1763 types in this page.
1764 .RE
1765 .\"------------------------------------- uintptr_t --------------------/
1766 .TP
1767 .I uintptr_t
1768 .RS
1769 .IR Include :
1770 .IR <stdint.h> .
1771 Alternatively,
1772 .IR <inttypes.h> .
1773 .PP
1774 An unsigned integer type
1775 such that any valid
1776 .RI ( "void *" )
1777 value can be converted to this type and back.
1778 According to the C language standard, it shall be
1779 capable of storing values in the range [0,
1780 .BR UINTPTR_MAX ].
1781 .PP
1782 The length modifier for
1783 .I uintptr_t
1784 for the
1785 .BR printf (3)
1786 family of functions
1787 is expanded by the macros
1788 .BR PRIuPTR ,
1789 .BR PRIoPTR ,
1790 .BR PRIxPTR ,
1791 and
1792 .B PRIXPTR
1793 (defined in
1794 .IR <inttypes.h> );
1795 resulting commonly in
1796 .B %"PRIuPTR"
1797 or
1798 .B %"PRIxPTR"
1799 for printing
1800 .I uintptr_t
1801 values.
1802 The length modifier for
1803 .I uintptr_t
1804 for the
1805 .BR scanf (3)
1806 family of functions
1807 is expanded by the macros
1808 .BR SCNuPTR,
1809 .BR SCNoPTR,
1810 .BR SCNxPTR ,
1811 and
1812 .B SCNXPTR
1813 (defined in
1814 .IR <inttypes.h> );
1815 resulting commonly in
1816 .B %"SCNuPTR"
1817 or
1818 .B %"SCNxPTR"
1819 for scanning
1820 .I uintptr_t
1821 values.
1822 .PP
1823 .IR "Conforming to" :
1824 C99 and later; POSIX.1-2001 and later.
1825 .PP
1826 .IR "See also" :
1827 the
1828 .I intptr_t
1829 and
1830 .I void *
1831 types in this page.
1832 .RE
1833 .\"------------------------------------- va_list ----------------------/
1834 .TP
1835 .I va_list
1836 .RS
1837 .IR Include :
1838 .IR <stdarg> .
1839 Alternatively,
1840 .IR <stdio.h> ,
1841 or
1842 .IR <wchar.h> .
1843 .PP
1844 Used by functions with a varying number of arguments of varying types.
1845 The function must declare an object of type
1846 .I va_list
1847 which is used by the macros
1848 .BR va_start (3),
1849 .BR va_arg (3),
1850 .BR va_copy (3),
1851 and
1852 .BR va_end (3)
1853 to traverse the list of arguments.
1854 .PP
1855 .IR "Conforming to" :
1856 C99 and later; POSIX.1-2001 and later.
1857 .PP
1858 .IR "See also" :
1859 .BR va_start (3),
1860 .BR va_arg (3),
1861 .BR va_copy (3),
1862 .BR va_end (3)
1863 .RE
1864 .\"------------------------------------- void * -----------------------/
1865 .TP
1866 .I void *
1867 .RS
1868 According to the C language standard,
1869 a pointer to any object type may be converted to a pointer to
1870 .I void
1871 and back.
1872 POSIX further requires that any pointer,
1873 including pointers to functions,
1874 may be converted to a pointer to
1875 .I void
1876 and back.
1877 .PP
1878 Conversions from and to any other pointer type are done implicitly,
1879 not requiring casts at all.
1880 Note that this feature prevents any kind of type checking:
1881 the programmer should be careful not to convert a
1882 .I void *
1883 value to a type incompatible to that of the underlying data,
1884 because that would result in undefined behavior.
1885 .PP
1886 This type is useful in function parameters and return value
1887 to allow passing values of any type.
1888 The function will typically use some mechanism to know
1889 the real type of the data being passed via a pointer to
1890 .IR void .
1891 .PP
1892 A value of this type can't be dereferenced,
1893 as it would give a value of type
1894 .IR void ,
1895 which is not possible.
1896 Likewise, pointer arithmetic is not possible with this type.
1897 However, in GNU C, pointer arithmetic is allowed
1898 as an extension to the standard;
1899 this is done by treating the size of a
1900 .I void
1901 or of a function as 1.
1902 A consequence of this is that
1903 .I sizeof
1904 is also allowed on
1905 .I void
1906 and on function types, and returns 1.
1907 .PP
1908 The conversion specifier for
1909 .I void *
1910 for the
1911 .BR printf (3)
1912 and the
1913 .BR scanf (3)
1914 families of functions is
1915 .BR p .
1916 .PP
1917 .IR Versions :
1918 The POSIX requirement about compatibility between
1919 .I void *
1920 and function pointers was added in
1921 POSIX.1-2008 Technical Corrigendum 1 (2013).
1922 .PP
1923 .IR "Conforming to" :
1924 C99 and later; POSIX.1-2001 and later.
1925 .PP
1926 .IR "See also" :
1927 .BR malloc (3),
1928 .BR memcmp (3),
1929 .BR memcpy (3),
1930 .BR memset (3)
1931 .PP
1932 See also the
1933 .I intptr_t
1934 and
1935 .I uintptr_t
1936 types in this page.
1937 .RE
1938 .\"--------------------------------------------------------------------/
1939 .SH NOTES
1940 The structures described in this manual page shall contain,
1941 at least, the members shown in their definition, in no particular order.
1942 .PP
1943 Most of the integer types described in this page don't have
1944 a corresponding length modifier for the
1945 .BR printf (3)
1946 and the
1947 .BR scanf (3)
1948 families of functions.
1949 To print a value of an integer type that doesn't have a length modifier,
1950 it should be converted to
1951 .I intmax_t
1952 or
1953 .I uintmax_t
1954 by an explicit cast.
1955 To scan into a variable of an integer type
1956 that doesn't have a length modifier,
1957 an intermediate temporary variable of type
1958 .I intmax_t
1959 or
1960 .I uintmax_t
1961 should be used.
1962 When copying from the temporary variable to the destination variable,
1963 the value could overflow.
1964 If the type has upper and lower limits,
1965 the user should check that the value is within those limits,
1966 before actually copying the value.
1967 The example below shows how these conversions should be done.
1968 .SS Conventions used in this page
1969 In "Conforming to" we only concern ourselves with
1970 C99 and later and POSIX.1-2001 and later.
1971 Some types may be specified in earlier versions of one of these standards,
1972 but in the interests of simplicity we omit details from earlier standards.
1973 .PP
1974 In "Include", we first note the "primary" header(s) that
1975 define the type according to either the C or POSIX.1 standards.
1976 Under "Alternatively", we note additional headers that
1977 the standards specify shall define the type.
1978 .SH EXAMPLES
1979 The program shown below scans from a string and prints a value stored in
1980 a variable of an integer type that doesn't have a length modifier.
1981 The appropriate conversions from and to
1982 .IR intmax_t ,
1983 and the appropriate range checks,
1984 are used as explained in the notes section above.
1985 .PP
1986 .EX
1987 #include <stdint.h>
1988 #include <stdio.h>
1989 #include <stdlib.h>
1990 #include <sys/types.h>
1992 int
1993 main (void)
1994 {
1995 static const char *const str = "500000 us in half a second";
1996 suseconds_t us;
1997 intmax_t tmp;
1999 /* Scan the number from the string into the temporary variable. */
2001 sscanf(str, "%jd", &tmp);
2003 /* Check that the value is within the valid range of suseconds_t. */
2005 if (tmp < \-1 || tmp > 1000000) {
2006 fprintf(stderr, "Scanned value outside valid range!\en");
2007 exit(EXIT_FAILURE);
2008 }
2010 /* Copy the value to the suseconds_t variable \(aqus\(aq. */
2012 us = tmp;
2014 /* Even though suseconds_t can hold the value \-1, this isn\(aqt
2015 a sensible number of microseconds. */
2017 if (us < 0) {
2018 fprintf(stderr, "Scanned value shouldn\(aqt be negative!\en");
2019 exit(EXIT_FAILURE);
2020 }
2022 /* Print the value. */
2024 printf("There are %jd microseconds in half a second.\en",
2025 (intmax_t) us);
2027 exit(EXIT_SUCCESS);
2028 }
2029 .EE
2030 .SH SEE ALSO
2031 .BR feature_test_macros (7),
2032 .BR standards (7)