1<limits.h>(0P) POSIX Programmer's Manual <limits.h>(0P)
2
6 limits.h - implementation-defined constants
7
9 #include <limits.h>
10
12 Some of the functionality described on this reference page extends the
13 ISO C standard. Applications shall define the appropriate feature test
14 macro (see the System Interfaces volume of IEEE Std 1003.1-2001, Sec‐
15 tion 2.2, The Compilation Environment) to enable the visibility of
16 these symbols in this header.
17 Many of the symbols listed here are not defined by the
19 ISO/IEC 9899:1999 standard. Such symbols are not shown as CX shaded.
20 The <limits.h> header shall define various symbolic names. Different
22 categories of names are described below.
23 The names represent various limits on resources that the implementation
25 imposes on applications.
26 Implementations may choose any appropriate value for each limit, pro‐
28 vided it is not more restrictive than the Minimum Acceptable Values
29 listed below. Symbolic constant names beginning with _POSIX may be
30 found in <unistd.h> .
31 Applications should not assume any particular value for a limit. To
33 achieve maximum portability, an application should not require more
34 resource than the Minimum Acceptable Value quantity. However, an
35 application wishing to avail itself of the full amount of a resource
36 available on an implementation may make use of the value given in <lim‐
37 its.h> on that particular implementation, by using the symbolic names
38 listed below. It should be noted, however, that many of the listed lim‐
39 its are not invariant, and at runtime, the value of the limit may dif‐
40 fer from those given in this header, for the following reasons:
41 * The limit is pathname-dependent.
43 * The limit differs between the compile and runtime machines.
45 For these reasons, an application may use the fpathconf(), pathconf(),
47 and sysconf() functions to determine the actual value of a limit at
48 runtime.
49 The items in the list ending in _MIN give the most negative values that
51 the mathematical types are guaranteed to be capable of representing.
52 Numbers of a more negative value may be supported on some implementa‐
53 tions, as indicated by the <limits.h> header on the implementation, but
54 applications requiring such numbers are not guaranteed to be portable
55 to all implementations. For positive constants ending in _MIN, this
56 indicates the minimum acceptable value.
57 Runtime Invariant Values (Possibly Indeterminate)
59 A definition of one of the symbolic names in the following list shall
60 be omitted from <limits.h> on specific implementations where the corre‐
61 sponding value is equal to or greater than the stated minimum, but is
62 unspecified.
63 This indetermination might depend on the amount of available memory
65 space on a specific instance of a specific implementation. The actual
66 value supported by a specific instance shall be provided by the
67 sysconf() function.
68 {AIO_LISTIO_MAX}
70 Maximum number of I/O operations in a single list I/O call sup‐
72 ported by the implementation.
73 Minimum Acceptable Value: {_POSIX_AIO_LISTIO_MAX}
74 {AIO_MAX}
76 Maximum number of outstanding asynchronous I/O operations sup‐
78 ported by the implementation.
79 Minimum Acceptable Value: {_POSIX_AIO_MAX}
80 {AIO_PRIO_DELTA_MAX}
82 The maximum amount by which a process can decrease its asynchro‐
84 nous I/O priority level from its own scheduling priority.
85 Minimum Acceptable Value: 0
86 {ARG_MAX}
88 Maximum length of argument to the exec functions including envi‐
89 ronment data.
90 Minimum Acceptable Value: {_POSIX_ARG_MAX}
91 {ATEXIT_MAX}
93 Maximum number of functions that may be registered with
95 atexit().
96 Minimum Acceptable Value: 32
97 {CHILD_MAX}
99 Maximum number of simultaneous processes per real user ID.
100 Minimum Acceptable Value: {_POSIX_CHILD_MAX}
101 {DELAYTIMER_MAX}
103 Maximum number of timer expiration overruns.
105 Minimum Acceptable Value: {_POSIX_DELAYTIMER_MAX}
106 {HOST_NAME_MAX}
108 Maximum length of a host name (not including the terminating
109 null) as returned from the gethostname() function.
110 Minimum Acceptable Value: {_POSIX_HOST_NAME_MAX}
111 {IOV_MAX}
113 Maximum number of iovec structures that one process has avail‐
115 able for use with readv() or writev().
116 Minimum Acceptable Value: {_XOPEN_IOV_MAX}
117 {LOGIN_NAME_MAX}
119 Maximum length of a login name.
120 Minimum Acceptable Value: {_POSIX_LOGIN_NAME_MAX}
121 {MQ_OPEN_MAX}
123 The maximum number of open message queue descriptors a process
125 may hold.
126 Minimum Acceptable Value: {_POSIX_MQ_OPEN_MAX}
127 {MQ_PRIO_MAX}
129 The maximum number of message priorities supported by the imple‐
131 mentation.
132 Minimum Acceptable Value: {_POSIX_MQ_PRIO_MAX}
133 {OPEN_MAX}
135 Maximum number of files that one process can have open at any
136 one time.
137 Minimum Acceptable Value: {_POSIX_OPEN_MAX}
138 {PAGESIZE}
140 Size in bytes of a page.
141 Minimum Acceptable Value: 1
142 {PAGE_SIZE}
144 Equivalent to {PAGESIZE}. If either {PAGESIZE} or {PAGE_SIZE} is
146 defined, the other is defined with the same value.
147 {PTHREAD_DESTRUCTOR_ITERATIONS}
149 Maximum number of attempts made to destroy a thread's thread-
151 specific data values on thread exit.
152 Minimum Acceptable Value: {_POSIX_THREAD_DESTRUCTOR_ITERATIONS}
153 {PTHREAD_KEYS_MAX}
155 Maximum number of data keys that can be created by a process.
157 Minimum Acceptable Value: {_POSIX_THREAD_KEYS_MAX}
158 {PTHREAD_STACK_MIN}
160 Minimum size in bytes of thread stack storage.
162 Minimum Acceptable Value: 0
163 {PTHREAD_THREADS_MAX}
165 Maximum number of threads that can be created per process.
167 Minimum Acceptable Value: {_POSIX_THREAD_THREADS_MAX}
168 {RE_DUP_MAX}
170 The number of repeated occurrences of a BRE permitted by the
171 regexec() and regcomp() functions when using the interval nota‐
172 tion {\(m,n\}; see BREs Matching Multiple Characters .
173 Minimum Acceptable Value: {_POSIX2_RE_DUP_MAX}
174 {RTSIG_MAX}
176 Maximum number of realtime signals reserved for application use
178 in this implementation.
179 Minimum Acceptable Value: {_POSIX_RTSIG_MAX}
180 {SEM_NSEMS_MAX}
182 Maximum number of semaphores that a process may have.
184 Minimum Acceptable Value: {_POSIX_SEM_NSEMS_MAX}
185 {SEM_VALUE_MAX}
187 The maximum value a semaphore may have.
189 Minimum Acceptable Value: {_POSIX_SEM_VALUE_MAX}
190 {SIGQUEUE_MAX}
192 Maximum number of queued signals that a process may send and
194 have pending at the receiver(s) at any time.
195 Minimum Acceptable Value: {_POSIX_SIGQUEUE_MAX}
196 {SS_REPL_MAX}
198 The maximum number of replenishment operations that may be
200 simultaneously pending for a particular sporadic server sched‐
201 uler.
202 Minimum Acceptable Value: {_POSIX_SS_REPL_MAX}
203 {STREAM_MAX}
205 The number of streams that one process can have open at one
206 time. If defined, it has the same value as {FOPEN_MAX} (see
207 <stdio.h> ).
208 Minimum Acceptable Value: {_POSIX_STREAM_MAX}
209 {SYMLOOP_MAX}
211 Maximum number of symbolic links that can be reliably traversed
212 in the resolution of a pathname in the absence of a loop.
213 Minimum Acceptable Value: {_POSIX_SYMLOOP_MAX}
214 {TIMER_MAX}
216 Maximum number of timers per process supported by the implemen‐
218 tation.
219 Minimum Acceptable Value: {_POSIX_TIMER_MAX}
220 {TRACE_EVENT_NAME_MAX}
222 Maximum length of the trace event name.
224 Minimum Acceptable Value: {_POSIX_TRACE_EVENT_NAME_MAX}
225 {TRACE_NAME_MAX}
227 Maximum length of the trace generation version string or of the
229 trace stream name.
230 Minimum Acceptable Value: {_POSIX_TRACE_NAME_MAX}
231 {TRACE_SYS_MAX}
233 Maximum number of trace streams that may simultaneously exist in
235 the system.
236 Minimum Acceptable Value: {_POSIX_TRACE_SYS_MAX}
237 {TRACE_USER_EVENT_MAX}
239 Maximum number of user trace event type identifiers that may
241 simultaneously exist in a traced process, including the prede‐
242 fined user trace event POSIX_TRACE_UNNAMED_USER_EVENT.
243 Minimum Acceptable Value: {_POSIX_TRACE_USER_EVENT_MAX}
244 {TTY_NAME_MAX}
246 Maximum length of terminal device name.
247 Minimum Acceptable Value: {_POSIX_TTY_NAME_MAX}
248 {TZNAME_MAX}
250 Maximum number of bytes supported for the name of a timezone
251 (not of the TZ variable).
252 Minimum Acceptable Value: {_POSIX_TZNAME_MAX}
253 Note: The length given by {TZNAME_MAX} does not include the quoting
256 characters mentioned in Other Environment Variables .
257 Pathname Variable Values
260 The values in the following list may be constants within an implementa‐
261 tion or may vary from one pathname to another. For example, file sys‐
262 tems or directories may have different characteristics.
263 A definition of one of the values shall be omitted from the <limits.h>
265 header on specific implementations where the corresponding value is
266 equal to or greater than the stated minimum, but where the value can
267 vary depending on the file to which it is applied. The actual value
268 supported for a specific pathname shall be provided by the pathconf()
269 function.
270 {FILESIZEBITS}
272 Minimum number of bits needed to represent, as a signed integer
273 value, the maximum size of a regular file allowed in the speci‐
274 fied directory.
275 Minimum Acceptable Value: 32
276 {LINK_MAX}
278 Maximum number of links to a single file.
279 Minimum Acceptable Value: {_POSIX_LINK_MAX}
280 {MAX_CANON}
282 Maximum number of bytes in a terminal canonical input line.
283 Minimum Acceptable Value: {_POSIX_MAX_CANON}
284 {MAX_INPUT}
286 Minimum number of bytes for which space is available in a termi‐
287 nal input queue; therefore, the maximum number of bytes a con‐
288 forming application may require to be typed as input before
289 reading them.
290 Minimum Acceptable Value: {_POSIX_MAX_INPUT}
291 {NAME_MAX}
293 Maximum number of bytes in a filename (not including terminating
294 null).
295 Minimum Acceptable Value: {_POSIX_NAME_MAX}
296 Minimum Acceptable Value: {_XOPEN_NAME_MAX}
297 {PATH_MAX}
299 Maximum number of bytes in a pathname, including the terminating
300 null character.
301 Minimum Acceptable Value: {_POSIX_PATH_MAX}
302 Minimum Acceptable Value: {_XOPEN_PATH_MAX}
303 {PIPE_BUF}
305 Maximum number of bytes that is guaranteed to be atomic when
306 writing to a pipe.
307 Minimum Acceptable Value: {_POSIX_PIPE_BUF}
308 {POSIX_ALLOC_SIZE_MIN}
310 Minimum number of bytes of storage actually allocated for any
312 portion of a file.
313 Minimum Acceptable Value: Not specified.
314 {POSIX_REC_INCR_XFER_SIZE}
316 Recommended increment for file transfer sizes between the
318 {POSIX_REC_MIN_XFER_SIZE} and {POSIX_REC_MAX_XFER_SIZE} values.
319 Minimum Acceptable Value: Not specified.
320 {POSIX_REC_MAX_XFER_SIZE}
322 Maximum recommended file transfer size.
324 Minimum Acceptable Value: Not specified.
325 {POSIX_REC_MIN_XFER_SIZE}
327 Minimum recommended file transfer size.
329 Minimum Acceptable Value: Not specified.
330 {POSIX_REC_XFER_ALIGN}
332 Recommended file transfer buffer alignment.
334 Minimum Acceptable Value: Not specified.
335 {SYMLINK_MAX}
337 Maximum number of bytes in a symbolic link.
338 Minimum Acceptable Value: {_POSIX_SYMLINK_MAX}
339 Runtime Increasable Values
342 The magnitude limitations in the following list shall be fixed by spe‐
343 cific implementations. An application should assume that the value sup‐
344 plied by <limits.h> in a specific implementation is the minimum that
345 pertains whenever the application is run under that implementation. A
346 specific instance of a specific implementation may increase the value
347 relative to that supplied by <limits.h> for that implementation. The
348 actual value supported by a specific instance shall be provided by the
349 sysconf() function.
350 {BC_BASE_MAX}
352 Maximum obase values allowed by the bc utility.
353 Minimum Acceptable Value: {_POSIX2_BC_BASE_MAX}
354 {BC_DIM_MAX}
356 Maximum number of elements permitted in an array by the bc util‐
357 ity.
358 Minimum Acceptable Value: {_POSIX2_BC_DIM_MAX}
359 {BC_SCALE_MAX}
361 Maximum scale value allowed by the bc utility.
362 Minimum Acceptable Value: {_POSIX2_BC_SCALE_MAX}
363 {BC_STRING_MAX}
365 Maximum length of a string constant accepted by the bc utility.
366 Minimum Acceptable Value: {_POSIX2_BC_STRING_MAX}
367 {CHARCLASS_NAME_MAX}
369 Maximum number of bytes in a character class name.
370 Minimum Acceptable Value: {_POSIX2_CHARCLASS_NAME_MAX}
371 {COLL_WEIGHTS_MAX}
373 Maximum number of weights that can be assigned to an entry of
374 the LC_COLLATE order keyword in the locale definition file; see
375 Locale .
376 Minimum Acceptable Value: {_POSIX2_COLL_WEIGHTS_MAX}
377 {EXPR_NEST_MAX}
379 Maximum number of expressions that can be nested within paren‐
380 theses by the expr utility.
381 Minimum Acceptable Value: {_POSIX2_EXPR_NEST_MAX}
382 {LINE_MAX}
384 Unless otherwise noted, the maximum length, in bytes, of a util‐
385 ity's input line (either standard input or another file), when
386 the utility is described as processing text files. The length
387 includes room for the trailing <newline>.
388 Minimum Acceptable Value: {_POSIX2_LINE_MAX}
389 {NGROUPS_MAX}
391 Maximum number of simultaneous supplementary group IDs per
392 process.
393 Minimum Acceptable Value: {_POSIX_NGROUPS_MAX}
394 {RE_DUP_MAX}
396 Maximum number of repeated occurrences of a regular expression
397 permitted when using the interval notation \{m,n\}; see Regular
398 Expressions .
399 Minimum Acceptable Value: {_POSIX2_RE_DUP_MAX}
400 Maximum Values
403 The symbolic constants in the following list shall be defined in <lim‐
404 its.h> with the values shown. These are symbolic names for the most
405 restrictive value for certain features on an implementation supporting
406 the Timers option. A conforming implementation shall provide values no
407 larger than these values. A conforming application must not require a
408 smaller value for correct operation.
409 {_POSIX_CLOCKRES_MIN}
411 The resolution of the CLOCK_REALTIME clock, in nanoseconds.
413 Value: 20 000 000
414 If the Monotonic Clock option is supported, the resolution of the
416 CLOCK_MONOTONIC clock, in nanoseconds, is represented by {_POSIX_CLOCK‐
417 RES_MIN}.
418 Minimum Values
421 The symbolic constants in the following list shall be defined in <lim‐
422 its.h> with the values shown. These are symbolic names for the most
423 restrictive value for certain features on an implementation conforming
424 to this volume of IEEE Std 1003.1-2001. Related symbolic constants are
425 defined elsewhere in this volume of IEEE Std 1003.1-2001 which reflect
426 the actual implementation and which need not be as restrictive. A con‐
427 forming implementation shall provide values at least this large. A
428 strictly conforming application must not require a larger value for
429 correct operation.
430 {_POSIX_AIO_LISTIO_MAX}
432 The number of I/O operations that can be specified in a list I/O
434 call.
435 Value: 2
436 {_POSIX_AIO_MAX}
438 The number of outstanding asynchronous I/O operations.
440 Value: 1
441 {_POSIX_ARG_MAX}
443 Maximum length of argument to the exec functions including envi‐
444 ronment data.
445 Value: 4 096
446 {_POSIX_CHILD_MAX}
448 Maximum number of simultaneous processes per real user ID.
449 Value: 25
450 {_POSIX_DELAYTIMER_MAX}
452 The number of timer expiration overruns.
454 Value: 32
455 {_POSIX_HOST_NAME_MAX}
457 Maximum length of a host name (not including the terminating
458 null) as returned from the gethostname() function.
459 Value: 255
460 {_POSIX_LINK_MAX}
462 Maximum number of links to a single file.
463 Value: 8
464 {_POSIX_LOGIN_NAME_MAX}
466 The size of the storage required for a login name, in bytes,
467 including the terminating null.
468 Value: 9
469 {_POSIX_MAX_CANON}
471 Maximum number of bytes in a terminal canonical input queue.
472 Value: 255
473 {_POSIX_MAX_INPUT}
475 Maximum number of bytes allowed in a terminal input queue.
476 Value: 255
477 {_POSIX_MQ_OPEN_MAX}
479 The number of message queues that can be open for a single
481 process.
482 Value: 8
483 {_POSIX_MQ_PRIO_MAX}
485 The maximum number of message priorities supported by the imple‐
487 mentation.
488 Value: 32
489 {_POSIX_NAME_MAX}
491 Maximum number of bytes in a filename (not including terminating
492 null).
493 Value: 14
494 {_POSIX_NGROUPS_MAX}
496 Maximum number of simultaneous supplementary group IDs per
497 process.
498 Value: 8
499 {_POSIX_OPEN_MAX}
501 Maximum number of files that one process can have open at any
502 one time.
503 Value: 20
504 {_POSIX_PATH_MAX}
506 Maximum number of bytes in a pathname.
507 Value: 256
508 {_POSIX_PIPE_BUF}
510 Maximum number of bytes that is guaranteed to be atomic when
511 writing to a pipe.
512 Value: 512
513 {_POSIX_RE_DUP_MAX}
515 The number of repeated occurrences of a BRE permitted by the
516 regexec() and regcomp() functions when using the interval nota‐
517 tion {\(m,n\}; see BREs Matching Multiple Characters .
518 Value: 255
519 {_POSIX_RTSIG_MAX}
521 The number of realtime signal numbers reserved for application
523 use.
524 Value: 8
525 {_POSIX_SEM_NSEMS_MAX}
527 The number of semaphores that a process may have.
529 Value: 256
530 {_POSIX_SEM_VALUE_MAX}
532 The maximum value a semaphore may have.
534 Value: 32 767
535 {_POSIX_SIGQUEUE_MAX}
537 The number of queued signals that a process may send and have
539 pending at the receiver(s) at any time.
540 Value: 32
541 {_POSIX_SSIZE_MAX}
543 The value that can be stored in an object of type ssize_t.
544 Value: 32 767
545 {_POSIX_STREAM_MAX}
547 The number of streams that one process can have open at one
548 time.
549 Value: 8
550 {_POSIX_SS_REPL_MAX}
552 The number of replenishment operations that may be simultane‐
554 ously pending for a particular sporadic server scheduler.
555 Value: 4
556 {_POSIX_SYMLINK_MAX}
558 The number of bytes in a symbolic link.
559 Value: 255
560 {_POSIX_SYMLOOP_MAX}
562 The number of symbolic links that can be traversed in the reso‐
563 lution of a pathname in the absence of a loop.
564 Value: 8
565 {_POSIX_THREAD_DESTRUCTOR_ITERATIONS}
567 The number of attempts made to destroy a thread's thread-spe‐
569 cific data values on thread exit.
570 Value: 4
571 {_POSIX_THREAD_KEYS_MAX}
573 The number of data keys per process.
575 Value: 128
576 {_POSIX_THREAD_THREADS_MAX}
578 The number of threads per process.
580 Value: 64
581 {_POSIX_TIMER_MAX}
583 The per-process number of timers.
585 Value: 32
586 {_POSIX_TRACE_EVENT_NAME_MAX}
588 The length in bytes of a trace event name.
590 Value: 30
591 {_POSIX_TRACE_NAME_MAX}
593 The length in bytes of a trace generation version string or a
595 trace stream name.
596 Value: 8
597 {_POSIX_TRACE_SYS_MAX}
599 The number of trace streams that may simultaneously exist in the
601 system.
602 Value: 8
603 {_POSIX_TRACE_USER_EVENT_MAX}
605 The number of user trace event type identifiers that may simul‐
607 taneously exist in a traced process, including the predefined
608 user trace event POSIX_TRACE_UNNAMED_USER_EVENT.
609 Value: 32
610 {_POSIX_TTY_NAME_MAX}
612 The size of the storage required for a terminal device name, in
613 bytes, including the terminating null.
614 Value: 9
615 {_POSIX_TZNAME_MAX}
617 Maximum number of bytes supported for the name of a timezone
618 (not of the TZ variable).
619 Value: 6
620 Note:
622 The length given by {_POSIX_TZNAME_MAX} does not include the
623 quoting characters mentioned in Other Environment Variables .
624 {_POSIX2_BC_BASE_MAX}
627 Maximum obase values allowed by the bc utility.
628 Value: 99
629 {_POSIX2_BC_DIM_MAX}
631 Maximum number of elements permitted in an array by the bc util‐
632 ity.
633 Value: 2 048
634 {_POSIX2_BC_SCALE_MAX}
636 Maximum scale value allowed by the bc utility.
637 Value: 99
638 {_POSIX2_BC_STRING_MAX}
640 Maximum length of a string constant accepted by the bc utility.
641 Value: 1 000
642 {_POSIX2_CHARCLASS_NAME_MAX}
644 Maximum number of bytes in a character class name.
645 Value: 14
646 {_POSIX2_COLL_WEIGHTS_MAX}
648 Maximum number of weights that can be assigned to an entry of
649 the LC_COLLATE order keyword in the locale definition file; see
650 Locale .
651 Value: 2
652 {_POSIX2_EXPR_NEST_MAX}
654 Maximum number of expressions that can be nested within paren‐
655 theses by the expr utility.
656 Value: 32
657 {_POSIX2_LINE_MAX}
659 Unless otherwise noted, the maximum length, in bytes, of a util‐
660 ity's input line (either standard input or another file), when
661 the utility is described as processing text files. The length
662 includes room for the trailing <newline>.
663 Value: 2 048
664 {_POSIX2_RE_DUP_MAX
666 Maximum number of repeated occurrences of a regular expression
667 permitted when using the interval notation \{m,n\}; see Regular
668 Expressions .
669 Value: 255
670 {_XOPEN_IOV_MAX}
672 Maximum number of iovec structures that one process has avail‐
674 able for use with readv() or writev().
675 Value: 16
676 {_XOPEN_NAME_MAX}
678 Maximum number of bytes in a filename (not including the termi‐
680 nating null).
681 Value: 255
682 {_XOPEN_PATH_MAX}
684 Maximum number of bytes in a pathname.
686 Value: 1024
687 Numerical Limits
690 The values in the following lists shall be defined in <limits.h> and
691 are constant expressions suitable for use in #if preprocessing direc‐
692 tives. Moreover, except for {CHAR_BIT}, {DBL_DIG}, {DBL_MAX},
693 {FLT_DIG}, {FLT_MAX}, {LONG_BIT}, {WORD_BIT}, and {MB_LEN_MAX}, the
694 symbolic names are defined as expressions of the correct type.
695 If the value of an object of type char is treated as a signed integer
697 when used in an expression, the value of {CHAR_MIN} is the same as that
698 of {SCHAR_MIN} and the value of {CHAR_MAX} is the same as that of
699 {SCHAR_MAX}. Otherwise, the value of {CHAR_MIN} is 0 and the value of
700 {CHAR_MAX} is the same as that of {UCHAR_MAX}.
701 {CHAR_BIT}
703 Number of bits in a type char.
704 Value: 8
705 {CHAR_MAX}
707 Maximum value of type char.
708 Value: {UCHAR_MAX} or {SCHAR_MAX}
709 {CHAR_MIN}
711 Minimum value of type char.
712 Value: {SCHAR_MIN} or 0
713 {INT_MAX}
715 Maximum value of an int.
716 Minimum Acceptable Value: 2 147 483 647
717 {LONG_BIT}
719 Number of bits in a long.
721 Minimum Acceptable Value: 32
722 {LONG_MAX}
724 Maximum value of a long.
725 Minimum Acceptable Value: +2 147 483 647
726 {MB_LEN_MAX}
728 Maximum number of bytes in a character, for any supported
729 locale.
730 Minimum Acceptable Value: 1
731 {SCHAR_MAX}
733 Maximum value of type signed char.
734 Value: +127
735 {SHRT_MAX}
737 Maximum value of type short.
738 Minimum Acceptable Value: +32 767
739 {SSIZE_MAX}
741 Maximum value of an object of type ssize_t.
742 Minimum Acceptable Value: {_POSIX_SSIZE_MAX}
743 {UCHAR_MAX}
745 Maximum value of type unsigned char.
746 Value: 255
747 {UINT_MAX}
749 Maximum value of type unsigned.
750 Minimum Acceptable Value: 4 294 967 295
751 {ULONG_MAX}
753 Maximum value of type unsigned long.
754 Minimum Acceptable Value: 4 294 967 295
755 {USHRT_MAX}
757 Maximum value for a type unsigned short.
758 Minimum Acceptable Value: 65 535
759 {WORD_BIT}
761 Number of bits in a word or type int.
763 Minimum Acceptable Value: 16
764 {INT_MIN}
766 Minimum value of type int.
767 Maximum Acceptable Value: -2 147 483 647
768 {LONG_MIN}
770 Minimum value of type long.
771 Maximum Acceptable Value: -2 147 483 647
772 {SCHAR_MIN}
774 Minimum value of type signed char.
775 Value: -128
776 {SHRT_MIN}
778 Minimum value of type short.
779 Maximum Acceptable Value: -32 767
780 {LLONG_MIN}
782 Minimum value of type long long.
783 Maximum Acceptable Value: -9223372036854775807
784 {LLONG_MAX}
786 Maximum value of type long long.
787 Minimum Acceptable Value: +9223372036854775807
788 {ULLONG_MAX}
790 Maximum value of type unsigned long long.
791 Minimum Acceptable Value: 18446744073709551615
792 Other Invariant Values
795 The following constants shall be defined on all implementations in
796 <limits.h>:
797 {CHARCLASS_NAME_MAX}
799 Maximum number of bytes in a character class name.
801 Minimum Acceptable Value: 14
802 {NL_ARGMAX}
804 Maximum value of digit in calls to the printf() and scanf()
806 functions.
807 Minimum Acceptable Value: 9
808 {NL_LANGMAX}
810 Maximum number of bytes in a LANG name.
812 Minimum Acceptable Value: 14
813 {NL_MSGMAX}
815 Maximum message number.
817 Minimum Acceptable Value: 32 767
818 {NL_NMAX}
820 Maximum number of bytes in an N-to-1 collation mapping.
822 Minimum Acceptable Value: No guaranteed value across all con‐
823 forming implementations.
824 {NL_SETMAX}
826 Maximum set number.
828 Minimum Acceptable Value: 255
829 {NL_TEXTMAX}
831 Maximum number of bytes in a message string.
833 Minimum Acceptable Value: {_POSIX2_LINE_MAX}
834 {NZERO}
836 Default process priority.
838 Minimum Acceptable Value: 20
839 The following sections are informative.
842
844 None.
845
847 A request was made to reduce the value of {_POSIX_LINK_MAX} from the
848 value of 8 specified for it in the POSIX.1-1990 standard to 2. The
849 standard developers decided to deny this request for several reasons:
850 * They wanted to avoid making any changes to the standard that could
852 break conforming applications, and the requested change could have
853 that effect.
854 * The use of multiple hard links to a file cannot always be replaced
856 with use of symbolic links. Symbolic links are semantically differ‐
857 ent from hard links in that they associate a pathname with another
858 pathname rather than a pathname with a file. This has implications
859 for access control, file permanence, and transparency.
860 * The original standard developers had considered the issue of allow‐
862 ing for implementations that did not in general support hard links,
863 and decided that this would reduce consensus on the standard.
864 Systems that support historical versions of the development option of
866 the ISO POSIX-2 standard retain the name {_POSIX2_RE_DUP_MAX} as an
867 alias for {_POSIX_RE_DUP_MAX}.
868 {PATH_MAX}
870 IEEE PASC Interpretation 1003.1 #15 addressed the inconsistency
871 in the standard with the definition of pathname and the descrip‐
872 tion of {PATH_MAX}, allowing application writers to allocate
873 either {PATH_MAX} or {PATH_MAX}+1 bytes. The inconsistency has
874 been removed by correction to the {PATH_MAX} definition to
875 include the null character. With this change, applications that
876 previously allocated {PATH_MAX} bytes will continue to succeed.
877 {SYMLINK_MAX}
879 This symbol refers to space for data that is stored in the file
880 system, as opposed to {PATH_MAX} which is the length of a name
881 that can be passed to a function. In some existing implementa‐
882 tions, the filenames pointed to by symbolic links are stored in
883 the inodes of the links, so it is important that {SYMLINK_MAX}
884 not be constrained to be as large as {PATH_MAX}.
885
888 None.
889
891 The System Interfaces volume of IEEE Std 1003.1-2001, fpathconf(),
892 pathconf(), sysconf()
893
895 Portions of this text are reprinted and reproduced in electronic form
896 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
897 -- Portable Operating System Interface (POSIX), The Open Group Base
898 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
899 Electrical and Electronics Engineers, Inc and The Open Group. In the
900 event of any discrepancy between this version and the original IEEE and
901 The Open Group Standard, the original IEEE and The Open Group Standard
902 is the referee document. The original Standard can be obtained online
903 at http://www.opengroup.org/unix/online.html .
904IEEE/The Open Group 2003 <limits.h>(0P)