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6 .TH LIMITS.H 3HEAD "Apr 8, 2004"
7 .SH NAME
8 limits.h, limits \- implementation-defined constants
9 .SH SYNOPSIS
10 .LP
11 .nf
12 \fB#include <limits.h>\fR
13 .fi
15 .SH DESCRIPTION
16 .sp
17 .LP
18 The <\fBlimits.h\fR> header defines various symbolic names. Different
19 categories of names are described below.
20 .sp
21 .LP
22 The names represent various limits on resources that the implementation imposes
23 on applications. Symbolic constant names beginning with _POSIX can be found in
24 \fBunistd.h\fR(3HEAD).
25 .sp
26 .LP
27 Applications should not assume any particular value for a limit. An application
28 wishing to avail itself of the full amount of a resource available on an
29 implementation can make use of the value given in limits.h on that particular
30 implementation by using the symbolic names listed below. Many of the listed
31 limits are not invariant, and at runtime, the value of the limit might differ
32 from those given in this header, for the following reasons:
33 .RS +4
34 .TP
35 .ie t \(bu
36 .el o
37 The limit is pathname-dependent.
38 .RE
39 .RS +4
40 .TP
41 .ie t \(bu
42 .el o
43 The limit differs between the compile and runtime machines.
44 .RE
45 .sp
46 .LP
47 For these reasons, an application can use the \fBfpathconf\fR(2),
48 \fBpathconf\fR(2), and \fBsysconf\fR(3C) functions to determine the actual
49 value of a limit at runtime.
50 .SS "Runtime Invariant Values (Possibly Indeterminate)"
51 .sp
52 .ne 2
53 .na
54 \fB\fBAIO_LISTIO_MAX\fR\fR
55 .ad
56 .sp .6
57 .RS 4n
58 Maximum number of I/O operations in a single list I/O call supported by the
59 implementation.
60 .RE
62 .sp
63 .ne 2
64 .na
65 \fB\fBAIO_MAX\fR\fR
66 .ad
67 .sp .6
68 .RS 4n
69 Maximum number of outstanding asynchronous I/O operations supported by the
70 implementation.
71 .RE
73 .sp
74 .ne 2
75 .na
76 \fB\fBAIO_PRIO_DELTA_MAX\fR\fR
77 .ad
78 .sp .6
79 .RS 4n
80 The maximum amount by which a process can decrease its asynchronous I/O
81 priority level from its own scheduling priority.
82 .RE
84 .sp
85 .ne 2
86 .na
87 \fB\fBARG_MAX\fR\fR
88 .ad
89 .sp .6
90 .RS 4n
91 Maximum length of argument to the \fBexec\fR(2) functions including environment
92 data.
93 .RE
95 .sp
96 .ne 2
97 .na
98 \fB\fBATEXIT_MAX\fR\fR
99 .ad
100 .sp .6
101 .RS 4n
102 Maximum number of functions that can be registered with \fBatexit\fR(3C).
103 .RE
105 .sp
106 .ne 2
107 .na
108 \fB\fBCHILD_MAX\fR\fR
109 .ad
110 .sp .6
111 .RS 4n
112 Maximum number of simultaneous processes per real user ID.
113 .RE
115 .sp
116 .ne 2
117 .na
118 \fB\fBCLK_TCK\fR\fR
119 .ad
120 .sp .6
121 .RS 4n
122 Number of clock ticks per second returned by the \fBtimes\fR(2) function.
123 .RE
125 .sp
126 .ne 2
127 .na
128 \fB\fBDELAYTIMER_MAX\fR\fR
129 .ad
130 .sp .6
131 .RS 4n
132 Maximum number of timer expiration overruns.
133 .RE
135 .sp
136 .ne 2
137 .na
138 \fB\fBHOST_NAME_MAX\fR\fR
139 .ad
140 .sp .6
141 .RS 4n
142 Maximum length of a host name (not including the terminating null) as returned
143 from the \fBgethostname\fR(3C) function.
144 .RE
146 .sp
147 .ne 2
148 .na
149 \fB\fBIOV_MAX\fR\fR
150 .ad
151 .sp .6
152 .RS 4n
153 Maximum number of \fBiovec\fR structures that one process has available for use
154 with \fBread\fR(2) or \fBwrite\fR(2).
155 .RE
157 .sp
158 .ne 2
159 .na
160 \fB\fBLOGIN_NAME_MAX\fR\fR
161 .ad
162 .sp .6
163 .RS 4n
164 Maximum length of a login name.
165 .RE
167 .sp
168 .ne 2
169 .na
170 \fB\fBMQ_OPEN_MAX\fR\fR
171 .ad
172 .sp .6
173 .RS 4n
174 The maximum number of open message queue descriptors a process is allowed to
175 hold.
176 .RE
178 .sp
179 .ne 2
180 .na
181 \fB\fBLOGIN_NAME_MAX\fR\fR
182 .ad
183 .sp .6
184 .RS 4n
185 Maximum length of a login name.
186 .RE
188 .sp
189 .ne 2
190 .na
191 \fB\fBMQ_OPEN_MAX\fR\fR
192 .ad
193 .sp .6
194 .RS 4n
195 The maximum number of open message queue descriptors a process is allowed to
196 hold.
197 .RE
199 .sp
200 .ne 2
201 .na
202 \fB\fBMQ_PRIO_MAX\fR\fR
203 .ad
204 .sp .6
205 .RS 4n
206 The maximum number of message priorities supported by the implementation.
207 .RE
209 .sp
210 .ne 2
211 .na
212 \fB\fBOPEN_MAX\fR\fR
213 .ad
214 .sp .6
215 .RS 4n
216 Maximum number of files that one process can have open at any one time.
217 .RE
219 .sp
220 .ne 2
221 .na
222 \fB\fBPAGESIZE\fR\fR
223 .ad
224 .sp .6
225 .RS 4n
226 Size in bytes of a page.
227 .RE
229 .sp
230 .ne 2
231 .na
232 \fB\fBPAGE_SIZE\fR\fR
233 .ad
234 .sp .6
235 .RS 4n
236 Equivalent to \fBPAGESIZE\fR. If either \fBPAGESIZE\fR or \fBPAGE_SIZE\fR is
237 defined, the other is defined with the same value.
238 .RE
240 .sp
241 .ne 2
242 .na
243 \fB\fBPASS_MAX\fR\fR
244 .ad
245 .sp .6
246 .RS 4n
247 The maximum number of significant bytes in a password, not including the
248 terminating null.
249 .RE
251 .sp
252 .ne 2
253 .na
254 \fB\fBPTHREAD_DESTRUCTOR_ITERATIONS\fR\fR
255 .ad
256 .sp .6
257 .RS 4n
258 Maximum number of attempts made to destroy a thread's thread-specific data
259 values on thread exit.
260 .RE
262 .sp
263 .ne 2
264 .na
265 \fB\fBPTHREAD_KEYS_MAX\fR\fR
266 .ad
267 .sp .6
268 .RS 4n
269 Maximum number of data keys that can be created by a process.
270 .RE
272 .sp
273 .ne 2
274 .na
275 \fB\fBPTHREAD_STACK_MIN\fR\fR
276 .ad
277 .sp .6
278 .RS 4n
279 Minimum size in bytes of thread stack storage.
280 .RE
282 .sp
283 .ne 2
284 .na
285 \fB\fBPTHREAD_THREADS_MAX\fR\fR
286 .ad
287 .sp .6
288 .RS 4n
289 Maximum number of threads that can be created per process.
290 .RE
292 .sp
293 .ne 2
294 .na
295 \fB\fBRE_DUP_MAX\fR\fR
296 .ad
297 .sp .6
298 .RS 4n
299 The number of repeated occurrences of a BRE permitted by the \fBregexec\fR(3C)
300 and \fBregcomp\fR(3C) functions when using the interval notation
301 {\e(\fIm\fR,\fIn\fR\e}.
302 .RE
304 .sp
305 .ne 2
306 .na
307 \fB\fBRTSIG_MAX\fR\fR
308 .ad
309 .sp .6
310 .RS 4n
311 Maximum number of realtime signals reserved for application use in this
312 implementation.
313 .RE
315 .sp
316 .ne 2
317 .na
318 \fB\fBSEM_NSEMS_MAX\fR\fR
319 .ad
320 .sp .6
321 .RS 4n
322 Maximum number of semaphores that a process can have.
323 .RE
325 .sp
326 .ne 2
327 .na
328 \fB\fBSEM_VALUE_MAX\fR\fR
329 .ad
330 .sp .6
331 .RS 4n
332 The maximum value a semaphore can have.
333 .RE
335 .sp
336 .ne 2
337 .na
338 \fB\fBSIGQUEUE_MAX\fR\fR
339 .ad
340 .sp .6
341 .RS 4n
342 Maximum number of queued signals that a process can send and have pending at
343 the receiver(s) at any time.
344 .RE
346 .sp
347 .ne 2
348 .na
349 \fB\fBSS_REPL_MAX\fR\fR
350 .ad
351 .sp .6
352 .RS 4n
353 The maximum number of replenishment operations that may be simultaneously
354 pending for a particular sporadic server scheduler.
355 .RE
357 .sp
358 .ne 2
359 .na
360 \fB\fBSTREAM_MAX\fR\fR
361 .ad
362 .sp .6
363 .RS 4n
364 The number of streams that one process can have open at one time. If defined,
365 it has the same value as \fBFOPEN_MAX\fR.
366 .RE
368 .sp
369 .ne 2
370 .na
371 \fB\fBSYMLOOP_MAX\fR\fR
372 .ad
373 .sp .6
374 .RS 4n
375 Maximum number of symbolic links that can be reliably traversed in the
376 resolution of a pathname in the absence of a loop.
377 .RE
379 .sp
380 .ne 2
381 .na
382 \fB\fBTIMER_MAX\fR\fR
383 .ad
384 .sp .6
385 .RS 4n
386 Maximum number of timers per process supported by the implementation.
387 .RE
389 .sp
390 .ne 2
391 .na
392 \fB\fBTRACE_EVENT_NAME_MAX\fR\fR
393 .ad
394 .sp .6
395 .RS 4n
396 Maximum length of the trace event name.
397 .RE
399 .sp
400 .ne 2
401 .na
402 \fB\fBTRACE_NAME_MAX\fR\fR
403 .ad
404 .sp .6
405 .RS 4n
406 Maximum length of the trace generation version string or of the trace stream
407 name.
408 .RE
410 .sp
411 .ne 2
412 .na
413 \fB\fBTRACE_SYS_MAX\fR\fR
414 .ad
415 .sp .6
416 .RS 4n
417 Maximum number of trace streams that may simultaneously exist in the system.
418 .RE
420 .sp
421 .ne 2
422 .na
423 \fB\fBTRACE_USER_EVENT_MAX\fR\fR
424 .ad
425 .sp .6
426 .RS 4n
427 Maximum number of user trace event type identifiers that may simultaneously
428 exist in a traced process, including the predefined user trace event
429 \fBPOSIX_TRACE_UNNAMED_USER_EVENT\fR.
430 .RE
432 .sp
433 .ne 2
434 .na
435 \fB\fBTTY_NAME_MAX\fR\fR
436 .ad
437 .sp .6
438 .RS 4n
439 Maximum length of terminal device name.
440 .RE
442 .sp
443 .ne 2
444 .na
445 \fB\fBTZNAME_MAX\fR\fR
446 .ad
447 .sp .6
448 .RS 4n
449 Maximum number of bytes supported for the name of a timezone (not of the TZ
450 variable).
451 .RE
453 .SS "Pathname Variable Values"
454 .sp
455 .LP
456 The values in the following list can be constants within an implementation or
457 can vary from one pathname to another. For example, file systems or directories
458 can have different characteristics. The value supported for a specific pathname
459 is provided by the \fBpathconf\fR(2) function.
460 .sp
461 .ne 2
462 .na
463 \fB\fBFILESIZEBITS\fR\fR
464 .ad
465 .RS 28n
466 Minimum number of bits needed to represent, as a signed integer value, the
467 maximum size of a regular file allowed in the specified directory.
468 .RE
470 .sp
471 .ne 2
472 .na
473 \fB\fBLINK_MAX\fR\fR
474 .ad
475 .RS 28n
476 Maximum number of links to a single file.
477 .RE
479 .sp
480 .ne 2
481 .na
482 \fB\fBMAX_CANON\fR\fR
483 .ad
484 .RS 28n
485 Maximum number of bytes in a terminal canonical input line.
486 .RE
488 .sp
489 .ne 2
490 .na
491 \fB\fBMAX_INPUT\fR\fR
492 .ad
493 .RS 28n
494 Minimum number of bytes for which space is available in a terminal input queue;
495 therefore, the maximum number of bytes a conforming application may require to
496 be typed as input before reading them.
497 .RE
499 .sp
500 .ne 2
501 .na
502 \fB\fBNAME_MAX\fR\fR
503 .ad
504 .RS 28n
505 Maximum number of bytes in a filename (not including terminating null).
506 .RE
508 .sp
509 .ne 2
510 .na
511 \fB\fBPATH_MAX\fR\fR
512 .ad
513 .RS 28n
514 Maximum number of bytes in a pathname, including the terminating null
515 character.
516 .RE
518 .sp
519 .ne 2
520 .na
521 \fB\fBPIPE_BUF\fR\fR
522 .ad
523 .RS 28n
524 Maximum number of bytes that is guaranteed to be atomic when writing to a pipe.
525 .RE
527 .sp
528 .ne 2
529 .na
530 \fB\fBPOSIX_ALLOC_SIZE_MIN\fR\fR
531 .ad
532 .RS 28n
533 Minimum number of bytes of storage actually allocated for any portion of a
534 file.
535 .RE
537 .sp
538 .ne 2
539 .na
540 \fB\fBPOSIX_REC_INCR_XFER_SIZE\fR\fR
541 .ad
542 .RS 28n
543 Recommended increment for file transfer sizes between the
544 \fBPOSIX_REC_MIN_XFER_SIZE\fR and \fBPOSIX_REC_MAX_XFER_SIZE\fR values.
545 .RE
547 .sp
548 .ne 2
549 .na
550 \fB\fBPOSIX_REC_MAX_XFER_SIZE\fR\fR
551 .ad
552 .RS 28n
553 Maximum recommended file transfer size.
554 .RE
556 .sp
557 .ne 2
558 .na
559 \fB\fBPOSIX_REC_MIN_XFER_SIZE\fR\fR
560 .ad
561 .RS 28n
562 Minimum recommended file transfer size.
563 .RE
565 .sp
566 .ne 2
567 .na
568 \fB\fBPOSIX_REC_XFER_ALIGN\fR\fR
569 .ad
570 .RS 28n
571 Recommended file transfer buffer alignment.
572 .RE
574 .sp
575 .ne 2
576 .na
577 \fB\fBSYMLINK_MAX\fR\fR
578 .ad
579 .RS 28n
580 Maximum number of bytes in a symbolic link.
581 .RE
583 .SS "Runtime Increasable Values"
584 .sp
585 .LP
586 The magnitude limitations in the following list are fixed by specific
587 implementations. An application should assume that the value supplied by
588 <\fBlimits.h\fR> in a specific implementation is the minimum that pertains
589 whenever the application is run under that implementation. A specific instance
590 of a specific implementation can increase the value relative to that supplied
591 by <\fBlimits.h\fR> for that implementation. The actual value supported by a
592 specific instance is provided by the \fBsysconf\fR(3C) function.
593 .sp
594 .ne 2
595 .na
596 \fB\fBBC_BASE_MAX\fR\fR
597 .ad
598 .RS 22n
599 Maximum obase values allowed by the \fBbc\fR(1) utility.
600 .RE
602 .sp
603 .ne 2
604 .na
605 \fB\fBBC_DIM_MAX\fR\fR
606 .ad
607 .RS 22n
608 Maximum number of elements permitted in an array by the \fBbc\fR utility.
609 .RE
611 .sp
612 .ne 2
613 .na
614 \fB\fBBC_SCALE_MAX\fR\fR
615 .ad
616 .RS 22n
617 Maximum scale value allowed by the \fBbc\fR utility.
618 .RE
620 .sp
621 .ne 2
622 .na
623 \fB\fBBC_STRING_MAX\fR\fR
624 .ad
625 .RS 22n
626 Maximum length of a string constant accepted by the \fBbc\fR utility.
627 .RE
629 .sp
630 .ne 2
631 .na
632 \fB\fBCHARCLASS_NAME_MAX\fR\fR
633 .ad
634 .RS 22n
635 Maximum number of bytes in a character class name.
636 .RE
638 .sp
639 .ne 2
640 .na
641 \fB\fBCOLL_WEIGHTS_MAX\fR\fR
642 .ad
643 .RS 22n
644 Maximum number of weights that can be assigned to an entry of the
645 \fBLC_COLLATE\fR order keyword in the locale definition file.
646 .RE
648 .sp
649 .ne 2
650 .na
651 \fB\fBEXPR_NEST_MAX\fR\fR
652 .ad
653 .RS 22n
654 Maximum number of expressions that can be nested within parentheses by the
655 \fBexpr\fR(1) utility.
656 .RE
658 .sp
659 .ne 2
660 .na
661 \fB\fBEXPR_NEST_MAX\fR\fR
662 .ad
663 .RS 22n
664 Maximum number of expressions that can be nested within parentheses by the
665 \fBexpr\fR utility.
666 .RE
668 .sp
669 .ne 2
670 .na
671 \fB\fBLINE_MAX\fR\fR
672 .ad
673 .RS 22n
674 Unless otherwise noted, the maximum length, in bytes, of a utility's input line
675 (either standard input or another file), when the utility is described as
676 processing text files. The length includes room for the trailing <newline>.
677 .RE
679 .sp
680 .ne 2
681 .na
682 \fB\fBNGROUPS_MAX\fR\fR
683 .ad
684 .RS 22n
685 Maximum number of simultaneous supplementary group IDs per process.
686 .RE
688 .sp
689 .ne 2
690 .na
691 \fB\fBRE_DUP_MAX\fR\fR
692 .ad
693 .RS 22n
694 Maximum number of repeated occurrences of a regular expression permitted when
695 using the interval notation \e{\fIm\fR,\fIn\fR\e}.
696 .RE
698 .SS "Maximum Values"
699 .sp
700 .LP
701 The symbolic constants in the following list are symbolic names for the most
702 restrictive value for certain features on an implementation supporting the
703 POSIX Timers option.
704 .sp
705 .ne 2
706 .na
707 \fB\fB_POSIX_CLOCKRES_MIN\fR\fR
708 .ad
709 .RS 23n
710 The resolution of the \fBCLOCK_REALTIME\fR clock, in nanoseconds.
711 .RE
713 .SS "Minimum Values"
714 .sp
715 .LP
716 The symbolic constants in the following list are symbolic names for the most
717 restrictive value for certain features on an implementation conforming to
718 various POSIX and Single Unix Specification requirements. See
719 \fBstandards\fR(5).
720 .sp
721 .ne 2
722 .na
723 \fB\fB_POSIX_AIO_LISTIO_MAX\fR\fR
724 .ad
725 .sp .6
726 .RS 4n
727 The number of I/O operations that can be specified in a list I/O call.
728 .RE
730 .sp
731 .ne 2
732 .na
733 \fB\fB_POSIX_AIO_MAX\fR\fR
734 .ad
735 .sp .6
736 .RS 4n
737 The number of outstanding asynchronous I/O operations.
738 .RE
740 .sp
741 .ne 2
742 .na
743 \fB\fB_POSIX_ARG_MAX\fR\fR
744 .ad
745 .sp .6
746 .RS 4n
747 Maximum length of argument to the \fBexec\fR(2) functions including environment
748 data.
749 .RE
751 .sp
752 .ne 2
753 .na
754 \fB\fB_POSIX_CHILD_MAX\fR\fR
755 .ad
756 .sp .6
757 .RS 4n
758 Maximum number of simultaneous processes per real user ID.
759 .RE
761 .sp
762 .ne 2
763 .na
764 \fB\fB_POSIX_DELAYTIMER_MAX\fR\fR
765 .ad
766 .sp .6
767 .RS 4n
768 The number of timer expiration overruns.
769 .RE
771 .sp
772 .ne 2
773 .na
774 \fB\fB_POSIX_HOST_NAME_MAX\fR\fR
775 .ad
776 .sp .6
777 .RS 4n
778 Maximum length of a host name (not including the terminating null) as returned
779 from the \fBgethostname\fR(3C) function.
780 .RE
782 .sp
783 .ne 2
784 .na
785 \fB\fB_POSIX_LINK_MAX\fR\fR
786 .ad
787 .sp .6
788 .RS 4n
789 Maximum number of links to a single file.
790 .RE
792 .sp
793 .ne 2
794 .na
795 \fB\fB_POSIX_LOGIN_NAME_MAX\fR\fR
796 .ad
797 .sp .6
798 .RS 4n
799 The size of the storage required for a login name, in bytes, including the
800 terminating null.
801 .RE
803 .sp
804 .ne 2
805 .na
806 \fB\fB_POSIX_MAX_CANON\fR\fR
807 .ad
808 .sp .6
809 .RS 4n
810 Maximum number of bytes in a terminal canonical input queue.
811 .RE
813 .sp
814 .ne 2
815 .na
816 \fB\fB_POSIX_MAX_INPUT\fR\fR
817 .ad
818 .sp .6
819 .RS 4n
820 Maximum number of bytes allowed in a terminal input queue.
821 .RE
823 .sp
824 .ne 2
825 .na
826 \fB\fB_POSIX_MQ_OPEN_MAX\fR\fR
827 .ad
828 .sp .6
829 .RS 4n
830 The number of message queues that can be open for a single process.
831 .RE
833 .sp
834 .ne 2
835 .na
836 \fB\fB_POSIX_MQ_PRIO_MAX\fR\fR
837 .ad
838 .sp .6
839 .RS 4n
840 The maximum number of message priorities supported by the implementation.
841 .RE
843 .sp
844 .ne 2
845 .na
846 \fB\fB_POSIX_NAME_MAX\fR\fR
847 .ad
848 .sp .6
849 .RS 4n
850 Maximum number of bytes in a filename (not including terminating null).
851 .RE
853 .sp
854 .ne 2
855 .na
856 \fB\fB_POSIX_NGROUPS_MAX\fR\fR
857 .ad
858 .sp .6
859 .RS 4n
860 Maximum number of simultaneous supplementary group IDs per process.
861 .RE
863 .sp
864 .ne 2
865 .na
866 \fB\fB_POSIX_OPEN_MAX\fR\fR
867 .ad
868 .sp .6
869 .RS 4n
870 Maximum number of files that one process can have open at any one time.
871 .RE
873 .sp
874 .ne 2
875 .na
876 \fB\fB_POSIX_PATH_MAX\fR\fR
877 .ad
878 .sp .6
879 .RS 4n
880 Maximum number of bytes in a pathname.
881 .RE
883 .sp
884 .ne 2
885 .na
886 \fB\fB_POSIX_PIPE_BUF\fR\fR
887 .ad
888 .sp .6
889 .RS 4n
890 Maximum number of bytes that is guaranteed to be atomic when writing to a pipe.
891 .RE
893 .sp
894 .ne 2
895 .na
896 \fB\fB_POSIX_RE_DUP_MAX\fR\fR
897 .ad
898 .sp .6
899 .RS 4n
900 The number of repeated occurrences of a BRE permitted by the \fBregexec()\fR
901 and \fBregcomp()\fR functions when using the interval notation
902 {\e(\fIm\fR,\fIn\fR\e}
903 .RE
905 .sp
906 .ne 2
907 .na
908 \fB\fB_POSIX_RTSIG_MAX\fR\fR
909 .ad
910 .sp .6
911 .RS 4n
912 The number of realtime signal numbers reserved for application use.
913 .RE
915 .sp
916 .ne 2
917 .na
918 \fB\fB_POSIX_SEM_NSEMS_MAX\fR\fR
919 .ad
920 .sp .6
921 .RS 4n
922 The number of semaphores that a process can have.
923 .RE
925 .sp
926 .ne 2
927 .na
928 \fB\fB_POSIX_SEM_VALUE_MAX\fR\fR
929 .ad
930 .sp .6
931 .RS 4n
932 The maximum value a semaphore can have.
933 .RE
935 .sp
936 .ne 2
937 .na
938 \fB\fB_POSIX_SIGQUEUE_MAX\fR\fR
939 .ad
940 .sp .6
941 .RS 4n
942 The number of queued signals that a process can send and have pending at the
943 receiver(s) at any time.
944 .RE
946 .sp
947 .ne 2
948 .na
949 \fB\fB_POSIX_SSIZE_MAX\fR\fR
950 .ad
951 .sp .6
952 .RS 4n
953 The value that can be stored in an object of type \fBssize_t\fR.
954 .RE
956 .sp
957 .ne 2
958 .na
959 \fB\fB_POSIX_STREAM_MAX\fR\fR
960 .ad
961 .sp .6
962 .RS 4n
963 The number of streams that one process can have open at one time.
964 .RE
966 .sp
967 .ne 2
968 .na
969 \fB\fB_POSIX_SS_REPL_MAX\fR\fR
970 .ad
971 .sp .6
972 .RS 4n
973 The number of replenishment operations that can be simultaneously pending for a
974 particular sporadic server scheduler.
975 .RE
977 .sp
978 .ne 2
979 .na
980 \fB\fB_POSIX_SYMLINK_MAX\fR\fR
981 .ad
982 .sp .6
983 .RS 4n
984 The number of bytes in a symbolic link.
985 .RE
987 .sp
988 .ne 2
989 .na
990 \fB\fB_POSIX_SYMLOOP_MAX\fR\fR
991 .ad
992 .sp .6
993 .RS 4n
994 The number of symbolic links that can be traversed in the resolution of a
995 pathname in the absence of a loop.
996 .RE
998 .sp
999 .ne 2
1000 .na
1001 \fB\fB_POSIX_THREAD_DESTRUCTOR_ITERATIONS\fR\fR
1002 .ad
1003 .sp .6
1004 .RS 4n
1005 The number of attempts made to destroy a thread's thread-specific data values
1006 on thread exit.
1007 .RE
1009 .sp
1010 .ne 2
1011 .na
1012 \fB\fB_POSIX_THREAD_KEYS_MAX\fR\fR
1013 .ad
1014 .sp .6
1015 .RS 4n
1016 The number of data keys per process.
1017 .RE
1019 .sp
1020 .ne 2
1021 .na
1022 \fB\fB_POSIX_THREAD_THREADS_MAX\fR\fR
1023 .ad
1024 .sp .6
1025 .RS 4n
1026 The number of threads per process.
1027 .RE
1029 .sp
1030 .ne 2
1031 .na
1032 \fB\fB_POSIX_TIMER_MAX\fR\fR
1033 .ad
1034 .sp .6
1035 .RS 4n
1036 The per-process number of timers.
1037 .RE
1039 .sp
1040 .ne 2
1041 .na
1042 \fB\fB_POSIX_TRACE_EVENT_NAME_MAX\fR\fR
1043 .ad
1044 .sp .6
1045 .RS 4n
1046 The length in bytes of a trace event name.
1047 .RE
1049 .sp
1050 .ne 2
1051 .na
1052 \fB\fB_POSIX_TRACE_NAME_MAX\fR\fR
1053 .ad
1054 .sp .6
1055 .RS 4n
1056 The length in bytes of a trace generation version string or a trace stream
1057 name.
1058 .RE
1060 .sp
1061 .ne 2
1062 .na
1063 \fB\fB_POSIX_TRACE_SYS_MAX\fR\fR
1064 .ad
1065 .sp .6
1066 .RS 4n
1067 The number of trace streams that can simultaneously exist in the system.
1068 .RE
1070 .sp
1071 .ne 2
1072 .na
1073 \fB\fB_POSIX_TRACE_USER_EVENT_MAX\fR\fR
1074 .ad
1075 .sp .6
1076 .RS 4n
1077 The number of user trace event type identifiers that may simultaneously exist
1078 in a traced process, including the predefined user trace event
1079 \fBPOSIX_TRACE_UNNAMED_USER_EVENT\fR.
1080 .RE
1082 .sp
1083 .ne 2
1084 .na
1085 \fB\fB_POSIX_TTY_NAME_MAX\fR\fR
1086 .ad
1087 .sp .6
1088 .RS 4n
1089 The size of the storage required for a terminal device name, in bytes,
1090 including the terminating null.
1091 .RE
1093 .sp
1094 .ne 2
1095 .na
1096 \fB\fB_POSIX_TZNAME_MAX\fR\fR
1097 .ad
1098 .sp .6
1099 .RS 4n
1100 Maximum number of bytes supported for the name of a timezone (not of the TZ
1101 variable).
1102 .RE
1104 .sp
1105 .ne 2
1106 .na
1107 \fB\fB_POSIX2_BC_BASE_MAX\fR\fR
1108 .ad
1109 .sp .6
1110 .RS 4n
1111 Maximum obase values allowed by the \fBbc\fR utility.
1112 .RE
1114 .sp
1115 .ne 2
1116 .na
1117 \fB\fB_POSIX2_BC_DIM_MAX\fR\fR
1118 .ad
1119 .sp .6
1120 .RS 4n
1121 Maximum number of elements permitted in an array by the \fBbc\fR utility.
1122 .RE
1124 .sp
1125 .ne 2
1126 .na
1127 \fB\fB_POSIX2_BC_SCALE_MAX\fR\fR
1128 .ad
1129 .sp .6
1130 .RS 4n
1131 Maximum scale value allowed by the \fBbc\fR utility.
1132 .RE
1134 .sp
1135 .ne 2
1136 .na
1137 \fB\fB_POSIX2_BC_STRING_MAX\fR\fR
1138 .ad
1139 .sp .6
1140 .RS 4n
1141 Maximum length of a string constant accepted by the \fBbc\fR utility.
1142 .RE
1144 .sp
1145 .ne 2
1146 .na
1147 \fB\fB_POSIX2_CHARCLASS_NAME_MAX\fR\fR
1148 .ad
1149 .sp .6
1150 .RS 4n
1151 Maximum number of bytes in a character class name.
1152 .RE
1154 .sp
1155 .ne 2
1156 .na
1157 \fB\fB_POSIX2_COLL_WEIGHTS_MAX\fR\fR
1158 .ad
1159 .sp .6
1160 .RS 4n
1161 Maximum number of weights that can be assigned to an entry of the
1162 \fBLC_COLLATE\fR order keyword in the locale definition file.
1163 .RE
1165 .sp
1166 .ne 2
1167 .na
1168 \fB\fB_POSIX2_EXPR_NEST_MAX\fR\fR
1169 .ad
1170 .sp .6
1171 .RS 4n
1172 Maximum number of expressions that can be nested within parentheses by the
1173 \fBexpr\fR utility.
1174 .RE
1176 .sp
1177 .ne 2
1178 .na
1179 \fB\fB_POSIX2_LINE_MAX\fR\fR
1180 .ad
1181 .sp .6
1182 .RS 4n
1183 Unless otherwise noted, the maximum length, in bytes, of a utility's input line
1184 (either standard input or another file), when the utility is described as
1185 processing text files. The length includes room for the trailing <newline>.
1186 .RE
1188 .sp
1189 .ne 2
1190 .na
1191 \fB\fB_POSIX2_RE_DUP_MAX\fR\fR
1192 .ad
1193 .sp .6
1194 .RS 4n
1195 Maximum number of repeated occurrences of a regular expression permitted when
1196 using the interval notation \e{\fIm\fR,\fIn\fR\e}.
1197 .RE
1199 .sp
1200 .ne 2
1201 .na
1202 \fB\fB_XOPEN_IOV_MAX\fR\fR
1203 .ad
1204 .sp .6
1205 .RS 4n
1206 Maximum number of \fBiovec\fR structures that one process has available for use
1207 with \fBread\fR(2) or \fBwrite\fR(2).
1208 .RE
1210 .sp
1211 .ne 2
1212 .na
1213 \fB\fB_XOPEN_NAME_MAX\fR\fR
1214 .ad
1215 .sp .6
1216 .RS 4n
1217 Maximum number of bytes in a filename (not including the terminating null).
1218 .RE
1220 .sp
1221 .ne 2
1222 .na
1223 \fB\fB_XOPEN_PATH_MAX\fR\fR
1224 .ad
1225 .sp .6
1226 .RS 4n
1227 Maximum number of bytes in a pathname.
1228 .RE
1230 .SS "Numerical Limits"
1231 .sp
1232 .LP
1233 The values in the following lists shall be defined in <\fBlimits.h\fR> and are
1234 constant expressions suitable for use in \fB#if\fR preprocessing directives.
1235 Moreover, except for \fBCHAR_BIT\fR, \fBDBL_DIG\fR, \fBDBL_MAX\fR,
1236 \fBFLT_DIG\fR, \fBFLT_MAX\fR, \fBLONG_BIT\fR, \fBWORD_BIT\fR, and
1237 \fBMB_LEN_MAX\fR, the symbolic names are defined as expressions of the correct
1238 type.
1239 .sp
1240 .LP
1241 If the value of an object of type \fBchar\fR is treated as a signed integer
1242 when used in an expression, the value of \fBCHAR_MIN\fR is the same as that of
1243 \fBSCHAR_MIN\fR and the value of \fBCHAR_MAX\fR is the same as that of
1244 \fBSCHAR_MAX\fR. Otherwise, the value of \fBCHAR_MIN\fR is 0 and the value of
1245 \fBCHAR_MAX\fR is the same as that of \fBUCHAR_MAX\fR.
1246 .sp
1247 .ne 2
1248 .na
1249 \fB\fBCHAR_BIT\fR\fR
1250 .ad
1251 .RS 14n
1252 Number of bits in a type \fBchar\fR.
1253 .RE
1255 .sp
1256 .ne 2
1257 .na
1258 \fB\fBCHAR_MAX\fR\fR
1259 .ad
1260 .RS 14n
1261 Maximum value of type \fBchar\fR.
1262 .RE
1264 .sp
1265 .ne 2
1266 .na
1267 \fB\fBCHAR_MIN\fR\fR
1268 .ad
1269 .RS 14n
1270 Minimum value of type \fBchar\fR.
1271 .RE
1273 .sp
1274 .ne 2
1275 .na
1276 \fB\fBDBL_DIG\fR\fR
1277 .ad
1278 .RS 14n
1279 Digits of precision of type \fBdouble\fR.
1280 .RE
1282 .sp
1283 .ne 2
1284 .na
1285 \fB\fBDBL_MAX\fR\fR
1286 .ad
1287 .RS 14n
1288 Maximum decimal value of a \fBdouble\fR.
1289 .RE
1291 .sp
1292 .ne 2
1293 .na
1294 \fB\fBDBL_MIN\fR\fR
1295 .ad
1296 .RS 14n
1297 Minimum decimal value of a \fBdouble\fR.
1298 .RE
1300 .sp
1301 .ne 2
1302 .na
1303 \fB\fBFLT_DIG\fR\fR
1304 .ad
1305 .RS 14n
1306 Digits of precision of type \fBfloat\fR.
1307 .RE
1309 .sp
1310 .ne 2
1311 .na
1312 \fB\fBFLT_MAX\fR\fR
1313 .ad
1314 .RS 14n
1315 Maximum decimal value of a \fBfloat\fR.
1316 .RE
1318 .sp
1319 .ne 2
1320 .na
1321 \fB\fBFLT_MIN\fR\fR
1322 .ad
1323 .RS 14n
1324 Minimum decimal value of a \fBfloat\fR.
1325 .RE
1327 .sp
1328 .ne 2
1329 .na
1330 \fB\fBINT_MIN\fR\fR
1331 .ad
1332 .RS 14n
1333 Minimum value of type \fBint\fR.
1334 .RE
1336 .sp
1337 .ne 2
1338 .na
1339 \fB\fBINT_MAX\fR\fR
1340 .ad
1341 .RS 14n
1342 Maximum value of an \fBint\fR.
1343 .RE
1345 .sp
1346 .ne 2
1347 .na
1348 \fB\fBLLONG_MIN\fR\fR
1349 .ad
1350 .RS 14n
1351 Minimum value of type \fBlong long\fR.
1352 .RE
1354 .sp
1355 .ne 2
1356 .na
1357 \fB\fBLLONG_MAX\fR\fR
1358 .ad
1359 .RS 14n
1360 Maximum value of type \fBlong long\fR.
1361 .RE
1363 .sp
1364 .ne 2
1365 .na
1366 \fB\fBLONG_BIT\fR\fR
1367 .ad
1368 .RS 14n
1369 Number of bits in a \fBlong\fR.
1370 .RE
1372 .sp
1373 .ne 2
1374 .na
1375 \fB\fBLONG_MIN\fR\fR
1376 .ad
1377 .RS 14n
1378 Minimum value of type \fBlong\fR.
1379 .RE
1381 .sp
1382 .ne 2
1383 .na
1384 \fB\fBLONG_MAX\fR\fR
1385 .ad
1386 .RS 14n
1387 Maximum value of a \fBlong\fR.
1388 .RE
1390 .sp
1391 .ne 2
1392 .na
1393 \fB\fBMB_LEN_MAX\fR\fR
1394 .ad
1395 .RS 14n
1396 Maximum number of bytes in a character, for any supported locale.
1397 .RE
1399 .sp
1400 .ne 2
1401 .na
1402 \fB\fBSCHAR_MIN\fR\fR
1403 .ad
1404 .RS 14n
1405 Minimum value of type \fBsigned char\fR.
1406 .RE
1408 .sp
1409 .ne 2
1410 .na
1411 \fB\fBSCHAR_MAX\fR\fR
1412 .ad
1413 .RS 14n
1414 Maximum value of type \fBsigned char\fR.
1415 .RE
1417 .sp
1418 .ne 2
1419 .na
1420 \fB\fBSHRT_MIN\fR\fR
1421 .ad
1422 .RS 14n
1423 Minimum value of type \fBshort\fR.
1424 .RE
1426 .sp
1427 .ne 2
1428 .na
1429 \fB\fBSHRT_MAX\fR\fR
1430 .ad
1431 .RS 14n
1432 Maximum value of type \fBshort\fR.
1433 .RE
1435 .sp
1436 .ne 2
1437 .na
1438 \fB\fBSSIZE_MAX\fR\fR
1439 .ad
1440 .RS 14n
1441 Maximum value of an object of type \fBssize_t\fR.
1442 .RE
1444 .sp
1445 .ne 2
1446 .na
1447 \fB\fBTMP_MAX\fR\fR
1448 .ad
1449 .RS 14n
1450 Minimum number of unique filename generated by \fBtmpnam\fR(3C). Maximum number
1451 of times an application can call \fBtmpnam()\fR reliably.
1452 .RE
1454 .sp
1455 .ne 2
1456 .na
1457 \fB\fBUCHAR_MAX\fR\fR
1458 .ad
1459 .RS 14n
1460 Maximum value of type \fBunsigned char\fR.
1461 .RE
1463 .sp
1464 .ne 2
1465 .na
1466 \fB\fBUINT_MAX\fR\fR
1467 .ad
1468 .RS 14n
1469 Maximum value of type \fBunsigned\fR.
1470 .RE
1472 .sp
1473 .ne 2
1474 .na
1475 \fB\fBULLONG_MAX\fR\fR
1476 .ad
1477 .RS 14n
1478 Maximum value of type unsigned \fBlong long\fR.
1479 .RE
1481 .sp
1482 .ne 2
1483 .na
1484 \fB\fBULONG_MAX\fR\fR
1485 .ad
1486 .RS 14n
1487 Maximum value of type \fBunsigned long\fR.
1488 .RE
1490 .sp
1491 .ne 2
1492 .na
1493 \fB\fBUSHRT_MAX\fR\fR
1494 .ad
1495 .RS 14n
1496 Maximum value for a type \fBunsigned short\fR.
1497 .RE
1499 .sp
1500 .ne 2
1501 .na
1502 \fB\fBWORD_BIT\fR\fR
1503 .ad
1504 .RS 14n
1505 Number of bits in a word or type \fBint\fR.
1506 .RE
1508 .SS "Other Invariant Values"
1509 .sp
1510 .LP
1511 The following constants are defined in <\fBlimits.h\fR>.
1512 .sp
1513 .ne 2
1514 .na
1515 \fB\fBCHARCLASS_NAME_MAX\fR\fR
1516 .ad
1517 .RS 22n
1518 Maximum number of bytes in a character class name.
1519 .RE
1521 .sp
1522 .ne 2
1523 .na
1524 \fB\fBLOGNAME_MAX\fR\fR
1525 .ad
1526 .RS 22n
1527 The maximum number of bytes supported in a user's login name.
1528 .RE
1530 .sp
1531 .ne 2
1532 .na
1533 \fB\fBNL_ARGMAX\fR\fR
1534 .ad
1535 .RS 22n
1536 Maximum value of digit in calls to the \fBprintf\fR(3C) and \fBscanf\fR(3C)
1537 functions.
1538 .RE
1540 .sp
1541 .ne 2
1542 .na
1543 \fB\fBNL_LANGMAX\fR\fR
1544 .ad
1545 .RS 22n
1546 Maximum number of bytes in a \fBLANG\fR name.
1547 .RE
1549 .sp
1550 .ne 2
1551 .na
1552 \fB\fBNL_MSGMAX\fR\fR
1553 .ad
1554 .RS 22n
1555 Maximum message number.
1556 .RE
1558 .sp
1559 .ne 2
1560 .na
1561 \fB\fBNL_NMAX\fR\fR
1562 .ad
1563 .RS 22n
1564 Maximum number of bytes in an N-to-1 collation mapping.
1565 .RE
1567 .sp
1568 .ne 2
1569 .na
1570 \fB\fBNL_SETMAX\fR\fR
1571 .ad
1572 .RS 22n
1573 Maximum set number.
1574 .RE
1576 .sp
1577 .ne 2
1578 .na
1579 \fB\fBNL_TEXTMAX\fR\fR
1580 .ad
1581 .RS 22n
1582 Maximum number of bytes in a message string.
1583 .RE
1585 .sp
1586 .ne 2
1587 .na
1588 \fB\fBNZERO\fR\fR
1589 .ad
1590 .RS 22n
1591 Default process priority.
1592 .RE
1594 .SH SEE ALSO
1595 .sp
1596 .LP
1597 \fBfpathconf\fR(2), \fBpathconf\fR(2), \fBsysconf\fR(3C), \fBstandards\fR(5)