1limits.h(0P) POSIX Programmer's Manual limits.h(0P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 limits.h — implementation-defined constants
14
16 #include <limits.h>
17
19 Some of the functionality described on this reference page extends the
20 ISO C standard. Applications shall define the appropriate feature test
21 macro (see the System Interfaces volume of POSIX.1‐2008, Section 2.2,
22 The Compilation Environment) to enable the visibility of these symbols
23 in this header.
24 Many of the symbols listed here are not defined by the
26 ISO/IEC 9899:1999 standard. Such symbols are not shown as CX shaded,
27 except under the heading ``Numerical Limits''.
28 The <limits.h> header shall define macros and symbolic constants for
30 various limits. Different categories of limits are described below,
31 representing various limits on resources that the implementation
32 imposes on applications. All macros and symbolic constants defined in
33 this header shall be suitable for use in #if preprocessing directives.
34 Implementations may choose any appropriate value for each limit, pro‐
36 vided it is not more restrictive than the Minimum Acceptable Values
37 listed below. Symbolic constant names beginning with _POSIX may be
38 found in <unistd.h>.
39 Applications should not assume any particular value for a limit. To
41 achieve maximum portability, an application should not require more
42 resource than the Minimum Acceptable Value quantity. However, an appli‐
43 cation wishing to avail itself of the full amount of a resource avail‐
44 able on an implementation may make use of the value given in <limits.h>
45 on that particular implementation, by using the macros and symbolic
46 constants listed below. It should be noted, however, that many of the
47 listed limits are not invariant, and at runtime, the value of the limit
48 may differ from those given in this header, for the following reasons:
49 * The limit is pathname-dependent.
51 * The limit differs between the compile and runtime machines.
53 For these reasons, an application may use the fpathconf(), pathconf(),
55 and sysconf() functions to determine the actual value of a limit at
56 runtime.
57 The items in the list ending in _MIN give the most negative values that
59 the mathematical types are guaranteed to be capable of representing.
60 Numbers of a more negative value may be supported on some implementa‐
61 tions, as indicated by the <limits.h> header on the implementation, but
62 applications requiring such numbers are not guaranteed to be portable
63 to all implementations. For positive constants ending in _MIN, this
64 indicates the minimum acceptable value.
65 Runtime Invariant Values (Possibly Indeterminate)
67 A definition of one of the symbolic constants in the following list
68 shall be omitted from <limits.h> on specific implementations where the
69 corresponding value is equal to or greater than the stated minimum, but
70 is unspecified.
71 This indetermination might depend on the amount of available memory
73 space on a specific instance of a specific implementation. The actual
74 value supported by a specific instance shall be provided by the
75 sysconf() function.
76 {AIO_LISTIO_MAX}
78 Maximum number of I/O operations in a single list I/O call sup‐
79 ported by the implementation.
80 Minimum Acceptable Value: {_POSIX_AIO_LISTIO_MAX}
81 {AIO_MAX}
83 Maximum number of outstanding asynchronous I/O operations sup‐
84 ported by the implementation.
85 Minimum Acceptable Value: {_POSIX_AIO_MAX}
86 {AIO_PRIO_DELTA_MAX}
88 The maximum amount by which a process can decrease its asynchro‐
89 nous I/O priority level from its own scheduling priority.
90 Minimum Acceptable Value: 0
91 {ARG_MAX}
93 Maximum length of argument to the exec functions including envi‐
94 ronment data.
95 Minimum Acceptable Value: {_POSIX_ARG_MAX}
96 {ATEXIT_MAX}
98 Maximum number of functions that may be registered with atexit().
99 Minimum Acceptable Value: 32
100 {CHILD_MAX}
102 Maximum number of simultaneous processes per real user ID.
103 Minimum Acceptable Value: {_POSIX_CHILD_MAX}
104 {DELAYTIMER_MAX}
106 Maximum number of timer expiration overruns.
107 Minimum Acceptable Value: {_POSIX_DELAYTIMER_MAX}
108 {HOST_NAME_MAX}
110 Maximum length of a host name (not including the terminating
111 null) as returned from the gethostname() function.
112 Minimum Acceptable Value: {_POSIX_HOST_NAME_MAX}
113 {IOV_MAX}
115 Maximum number of iovec structures that one process has available
116 for use with readv() or writev().
117 Minimum Acceptable Value: {_XOPEN_IOV_MAX}
118 {LOGIN_NAME_MAX}
120 Maximum length of a login name.
121 Minimum Acceptable Value: {_POSIX_LOGIN_NAME_MAX}
122 {MQ_OPEN_MAX}
124 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‐
130 mentation.
131 Minimum Acceptable Value: {_POSIX_MQ_PRIO_MAX}
132 {OPEN_MAX}
134 A value one greater than the maximum value that the system may
135 assign to a newly-created file descriptor.
136 Minimum Acceptable Value: {_POSIX_OPEN_MAX}
137 {PAGESIZE}
139 Size in bytes of a page.
140 Minimum Acceptable Value: 1
141 {PAGE_SIZE}
143 Equivalent to {PAGESIZE}. If either {PAGESIZE} or {PAGE_SIZE} is
144 defined, the other is defined with the same value.
145 {PTHREAD_DESTRUCTOR_ITERATIONS}
147 Maximum number of attempts made to destroy a thread's thread-spe‐
148 cific data values on thread exit.
149 Minimum Acceptable Value: {_POSIX_THREAD_DESTRUCTOR_ITERATIONS}
150 {PTHREAD_KEYS_MAX}
152 Maximum number of data keys that can be created by a process.
153 Minimum Acceptable Value: {_POSIX_THREAD_KEYS_MAX}
154 {PTHREAD_STACK_MIN}
156 Minimum size in bytes of thread stack storage.
157 Minimum Acceptable Value: 0
158 {PTHREAD_THREADS_MAX}
160 Maximum number of threads that can be created per process.
161 Minimum Acceptable Value: {_POSIX_THREAD_THREADS_MAX}
162 {RE_DUP_MAX}
164 Maximum number of repeated occurrences of a BRE or ERE interval
165 expression; see Section 9.3.6, BREs Matching Multiple Characters
166 and Section 9.4.6, EREs Matching Multiple Characters.
167 Minimum Acceptable Value: {_POSIX2_RE_DUP_MAX}
168 {RTSIG_MAX}
170 Maximum number of realtime signals reserved for application use
171 in this implementation.
172 Minimum Acceptable Value: {_POSIX_RTSIG_MAX}
173 {SEM_NSEMS_MAX}
175 Maximum number of semaphores that a process may have.
176 Minimum Acceptable Value: {_POSIX_SEM_NSEMS_MAX}
177 {SEM_VALUE_MAX}
179 The maximum value a semaphore may have.
180 Minimum Acceptable Value: {_POSIX_SEM_VALUE_MAX}
181 {SIGQUEUE_MAX}
183 Maximum number of queued signals that a process may send and have
184 pending at the receiver(s) at any time.
185 Minimum Acceptable Value: {_POSIX_SIGQUEUE_MAX}
186 {SS_REPL_MAX}
188 The maximum number of replenishment operations that may be simul‐
189 taneously pending for a particular sporadic server scheduler.
190 Minimum Acceptable Value: {_POSIX_SS_REPL_MAX}
191 {STREAM_MAX}
193 Maximum number of streams that one process can have open at one
194 time. If defined, it has the same value as {FOPEN_MAX} (see
195 <stdio.h>).
196 Minimum Acceptable Value: {_POSIX_STREAM_MAX}
197 {SYMLOOP_MAX}
199 Maximum number of symbolic links that can be reliably traversed
200 in the resolution of a pathname in the absence of a loop.
201 Minimum Acceptable Value: {_POSIX_SYMLOOP_MAX}
202 {TIMER_MAX}
204 Maximum number of timers per process supported by the implementa‐
205 tion.
206 Minimum Acceptable Value: {_POSIX_TIMER_MAX}
207 {TRACE_EVENT_NAME_MAX}
209 Maximum length of the trace event name (not including the termi‐
210 nating null).
211 Minimum Acceptable Value: {_POSIX_TRACE_EVENT_NAME_MAX}
212 {TRACE_NAME_MAX}
214 Maximum length of the trace generation version string or of the
215 trace stream name (not including the terminating null).
216 Minimum Acceptable Value: {_POSIX_TRACE_NAME_MAX}
217 {TRACE_SYS_MAX}
219 Maximum number of trace streams that may simultaneously exist in
220 the system.
221 Minimum Acceptable Value: {_POSIX_TRACE_SYS_MAX}
222 {TRACE_USER_EVENT_MAX}
224 Maximum number of user trace event type identifiers that may
225 simultaneously exist in a traced process, including the prede‐
226 fined user trace event POSIX_TRACE_UNNAMED_USER_EVENT.
227 Minimum Acceptable Value: {_POSIX_TRACE_USER_EVENT_MAX}
228 {TTY_NAME_MAX}
230 Maximum length of terminal device name.
231 Minimum Acceptable Value: {_POSIX_TTY_NAME_MAX}
232 {TZNAME_MAX}
234 Maximum number of bytes supported for the name of a timezone (not
235 of the TZ variable).
236 Minimum Acceptable Value: {_POSIX_TZNAME_MAX}
237 Note: The length given by {TZNAME_MAX} does not include the quoting
239 characters mentioned in Section 8.3, Other Environment Vari‐
240 ables.
241 Pathname Variable Values
243 The values in the following list may be constants within an implementa‐
244 tion or may vary from one pathname to another. For example, file sys‐
245 tems or directories may have different characteristics.
246 A definition of one of the symbolic constants in the following list
248 shall be omitted from the <limits.h> header on specific implementations
249 where the corresponding value is equal to or greater than the stated
250 minimum, but where the value can vary depending on the file to which it
251 is applied. The actual value supported for a specific pathname shall be
252 provided by the pathconf() function.
253 {FILESIZEBITS}
255 Minimum number of bits needed to represent, as a signed integer
256 value, the maximum size of a regular file allowed in the speci‐
257 fied directory.
258 Minimum Acceptable Value: 32
259 {LINK_MAX}
261 Maximum number of links to a single file.
262 Minimum Acceptable Value: {_POSIX_LINK_MAX}
263 {MAX_CANON}
265 Maximum number of bytes in a terminal canonical input line.
266 Minimum Acceptable Value: {_POSIX_MAX_CANON}
267 {MAX_INPUT}
269 Minimum number of bytes for which space is available in a termi‐
270 nal input queue; therefore, the maximum number of bytes a con‐
271 forming application may require to be typed as input before read‐
272 ing them.
273 Minimum Acceptable Value: {_POSIX_MAX_INPUT}
274 {NAME_MAX}
276 Maximum number of bytes in a filename (not including the termi‐
277 nating null of a filename string).
278 Minimum Acceptable Value: {_POSIX_NAME_MAX}
279 Minimum Acceptable Value: {_XOPEN_NAME_MAX}
280 {PATH_MAX}
282 Maximum number of bytes the implementation will store as a path‐
283 name in a user-supplied buffer of unspecified size, including the
284 terminating null character. Minimum number the implementation
285 will accept as the maximum number of bytes in a pathname.
286 Minimum Acceptable Value: {_POSIX_PATH_MAX}
287 Minimum Acceptable Value: {_XOPEN_PATH_MAX}
288 {PIPE_BUF}
290 Maximum number of bytes that is guaranteed to be atomic when
291 writing to a pipe.
292 Minimum Acceptable Value: {_POSIX_PIPE_BUF}
293 {POSIX_ALLOC_SIZE_MIN}
295 Minimum number of bytes of storage actually allocated for any
296 portion of a file.
297 Minimum Acceptable Value: Not specified.
298 {POSIX_REC_INCR_XFER_SIZE}
300 Recommended increment for file transfer sizes between the
301 {POSIX_REC_MIN_XFER_SIZE} and {POSIX_REC_MAX_XFER_SIZE} values.
302 Minimum Acceptable Value: Not specified.
303 {POSIX_REC_MAX_XFER_SIZE}
305 Maximum recommended file transfer size.
306 Minimum Acceptable Value: Not specified.
307 {POSIX_REC_MIN_XFER_SIZE}
309 Minimum recommended file transfer size.
310 Minimum Acceptable Value: Not specified.
311 {POSIX_REC_XFER_ALIGN}
313 Recommended file transfer buffer alignment.
314 Minimum Acceptable Value: Not specified.
315 {SYMLINK_MAX}
317 Maximum number of bytes in a symbolic link.
318 Minimum Acceptable Value: {_POSIX_SYMLINK_MAX}
319 Runtime Increasable Values
321 The magnitude limitations in the following list shall be fixed by spe‐
322 cific implementations. An application should assume that the value of
323 the symbolic constant defined by <limits.h> in a specific implementa‐
324 tion is the minimum that pertains whenever the application is run under
325 that implementation. A specific instance of a specific implementation
326 may increase the value relative to that supplied by <limits.h> for that
327 implementation. The actual value supported by a specific instance shall
328 be provided by the sysconf() function.
329 {BC_BASE_MAX}
331 Maximum obase values allowed by the bc utility.
332 Minimum Acceptable Value: {_POSIX2_BC_BASE_MAX}
333 {BC_DIM_MAX}
335 Maximum number of elements permitted in an array by the bc util‐
336 ity.
337 Minimum Acceptable Value: {_POSIX2_BC_DIM_MAX}
338 {BC_SCALE_MAX}
340 Maximum scale value allowed by the bc utility.
341 Minimum Acceptable Value: {_POSIX2_BC_SCALE_MAX}
342 {BC_STRING_MAX}
344 Maximum length of a string constant accepted by the bc utility.
345 Minimum Acceptable Value: {_POSIX2_BC_STRING_MAX}
346 {CHARCLASS_NAME_MAX}
348 Maximum number of bytes in a character class name.
349 Minimum Acceptable Value: {_POSIX2_CHARCLASS_NAME_MAX}
350 {COLL_WEIGHTS_MAX}
352 Maximum number of weights that can be assigned to an entry of the
353 LC_COLLATE order keyword in the locale definition file; see Chap‐
354 ter 7, Locale.
355 Minimum Acceptable Value: {_POSIX2_COLL_WEIGHTS_MAX}
356 {EXPR_NEST_MAX}
358 Maximum number of expressions that can be nested within parenthe‐
359 ses by the expr utility.
360 Minimum Acceptable Value: {_POSIX2_EXPR_NEST_MAX}
361 {LINE_MAX}
363 Unless otherwise noted, the maximum length, in bytes, of a util‐
364 ity's input line (either standard input or another file), when
365 the utility is described as processing text files. The length
366 includes room for the trailing <newline>.
367 Minimum Acceptable Value: {_POSIX2_LINE_MAX}
368 {NGROUPS_MAX}
370 Maximum number of simultaneous supplementary group IDs per
371 process.
372 Minimum Acceptable Value: {_POSIX_NGROUPS_MAX}
373 {RE_DUP_MAX}
375 Maximum number of repeated occurrences of a regular expression
376 permitted when using the interval notation \{m,n\}; see Chapter
377 9, Regular Expressions.
378 Minimum Acceptable Value: {_POSIX2_RE_DUP_MAX}
379 Maximum Values
381 The <limits.h> header shall define the following symbolic constants
382 with the values shown. These are the most restrictive values for cer‐
383 tain features on an implementation. A conforming implementation shall
384 provide values no larger than these values. A conforming application
385 must not require a smaller value for correct operation.
386 {_POSIX_CLOCKRES_MIN}
388 The resolution of the CLOCK_REALTIME clock, in nanoseconds.
389 Value: 20 000 000
390 If the Monotonic Clock option is supported, the resolution of the
392 CLOCK_MONOTONIC clock, in nanoseconds, is represented by
393 {_POSIX_CLOCKRES_MIN}.
394 Minimum Values
396 The <limits.h> header shall define the following symbolic constants
397 with the values shown. These are the most restrictive values for cer‐
398 tain features on an implementation conforming to this volume of
399 POSIX.1‐2008. Related symbolic constants are defined elsewhere in this
400 volume of POSIX.1‐2008 which reflect the actual implementation and
401 which need not be as restrictive. For each of these limits, a conform‐
402 ing implementation shall provide a value at least this large or shall
403 have no limit. A strictly conforming application must not require a
404 larger value for correct operation.
405 {_POSIX_AIO_LISTIO_MAX}
407 The number of I/O operations that can be specified in a list I/O
408 call.
409 Value: 2
410 {_POSIX_AIO_MAX}
412 The number of outstanding asynchronous I/O operations.
413 Value: 1
414 {_POSIX_ARG_MAX}
416 Maximum length of argument to the exec functions including envi‐
417 ronment data.
418 Value: 4 096
419 {_POSIX_CHILD_MAX}
421 Maximum number of simultaneous processes per real user ID.
422 Value: 25
423 {_POSIX_DELAYTIMER_MAX}
425 The number of timer expiration overruns.
426 Value: 32
427 {_POSIX_HOST_NAME_MAX}
429 Maximum length of a host name (not including the terminating
430 null) as returned from the gethostname() function.
431 Value: 255
432 {_POSIX_LINK_MAX}
434 Maximum number of links to a single file.
435 Value: 8
436 {_POSIX_LOGIN_NAME_MAX}
438 The size of the storage required for a login name, in bytes
439 (including the terminating null).
440 Value: 9
441 {_POSIX_MAX_CANON}
443 Maximum number of bytes in a terminal canonical input queue.
444 Value: 255
445 {_POSIX_MAX_INPUT}
447 Maximum number of bytes allowed in a terminal input queue.
448 Value: 255
449 {_POSIX_MQ_OPEN_MAX}
451 The number of message queues that can be open for a single
452 process.
453 Value: 8
454 {_POSIX_MQ_PRIO_MAX}
456 The maximum number of message priorities supported by the imple‐
457 mentation.
458 Value: 32
459 {_POSIX_NAME_MAX}
461 Maximum number of bytes in a filename (not including the termi‐
462 nating null of a filename string).
463 Value: 14
464 {_POSIX_NGROUPS_MAX}
466 Maximum number of simultaneous supplementary group IDs per
467 process.
468 Value: 8
469 {_POSIX_OPEN_MAX}
471 A value one greater than the maximum value that the system may
472 assign to a newly-created file descriptor.
473 Value: 20
474 {_POSIX_PATH_MAX}
476 Minimum number the implementation will accept as the maximum num‐
477 ber of bytes in a pathname.
478 Value: 256
479 {_POSIX_PIPE_BUF}
481 Maximum number of bytes that is guaranteed to be atomic when
482 writing to a pipe.
483 Value: 512
484 {_POSIX_RE_DUP_MAX}
486 The number of repeated occurrences of a BRE permitted by the
487 regexec() and regcomp() functions when using the interval nota‐
488 tion {\(m,n\}; see Section 9.3.6, BREs Matching Multiple Charac‐
489 ters.
490 Value: 255
491 {_POSIX_RTSIG_MAX}
493 The number of realtime signal numbers reserved for application
494 use.
495 Value: 8
496 {_POSIX_SEM_NSEMS_MAX}
498 The number of semaphores that a process may have.
499 Value: 256
500 {_POSIX_SEM_VALUE_MAX}
502 The maximum value a semaphore may have.
503 Value: 32 767
504 {_POSIX_SIGQUEUE_MAX}
506 The number of queued signals that a process may send and have
507 pending at the receiver(s) at any time.
508 Value: 32
509 {_POSIX_SSIZE_MAX}
511 The value that can be stored in an object of type ssize_t.
512 Value: 32 767
513 {_POSIX_SS_REPL_MAX}
515 The number of replenishment operations that may be simultaneously
516 pending for a particular sporadic server scheduler.
517 Value: 4
518 {_POSIX_STREAM_MAX}
520 The number of streams that one process can have open at one time.
521 Value: 8
522 {_POSIX_SYMLINK_MAX}
524 The number of bytes in a symbolic link.
525 Value: 255
526 {_POSIX_SYMLOOP_MAX}
528 The number of symbolic links that can be traversed in the resolu‐
529 tion of a pathname in the absence of a loop.
530 Value: 8
531 {_POSIX_THREAD_DESTRUCTOR_ITERATIONS}
533 The number of attempts made to destroy a thread's thread-specific
534 data values on thread exit.
535 Value: 4
536 {_POSIX_THREAD_KEYS_MAX}
538 The number of data keys per process.
539 Value: 128
540 {_POSIX_THREAD_THREADS_MAX}
542 The number of threads per process.
543 Value: 64
544 {_POSIX_TIMER_MAX}
546 The per-process number of timers.
547 Value: 32
548 {_POSIX_TRACE_EVENT_NAME_MAX}
550 The length in bytes of a trace event name (not including the ter‐
551 minating null).
552 Value: 30
553 {_POSIX_TRACE_NAME_MAX}
555 The length in bytes of a trace generation version string or a
556 trace stream name (not including the terminating null).
557 Value: 8
558 {_POSIX_TRACE_SYS_MAX}
560 The number of trace streams that may simultaneously exist in the
561 system.
562 Value: 8
563 {_POSIX_TRACE_USER_EVENT_MAX}
565 The number of user trace event type identifiers that may simulta‐
566 neously exist in a traced process, including the predefined user
567 trace event POSIX_TRACE_UNNAMED_USER_EVENT.
568 Value: 32
569 {_POSIX_TTY_NAME_MAX}
571 The size of the storage required for a terminal device name, in
572 bytes (including the terminating null).
573 Value: 9
574 {_POSIX_TZNAME_MAX}
576 Maximum number of bytes supported for the name of a timezone (not
577 of the TZ variable).
578 Value: 6
579 Note: The length given by {_POSIX_TZNAME_MAX} does not
581 include the quoting characters mentioned in Section
582 8.3, Other Environment Variables.
583 {_POSIX2_BC_BASE_MAX}
585 Maximum obase values allowed by the bc utility.
586 Value: 99
587 {_POSIX2_BC_DIM_MAX}
589 Maximum number of elements permitted in an array by the bc util‐
590 ity.
591 Value: 2 048
592 {_POSIX2_BC_SCALE_MAX}
594 Maximum scale value allowed by the bc utility.
595 Value: 99
596 {_POSIX2_BC_STRING_MAX}
598 Maximum length of a string constant accepted by the bc utility.
599 Value: 1 000
600 {_POSIX2_CHARCLASS_NAME_MAX}
602 Maximum number of bytes in a character class name.
603 Value: 14
604 {_POSIX2_COLL_WEIGHTS_MAX}
606 Maximum number of weights that can be assigned to an entry of the
607 LC_COLLATE order keyword in the locale definition file; see Chap‐
608 ter 7, Locale.
609 Value: 2
610 {_POSIX2_EXPR_NEST_MAX}
612 Maximum number of expressions that can be nested within parenthe‐
613 ses by the expr utility.
614 Value: 32
615 {_POSIX2_LINE_MAX}
617 Unless otherwise noted, the maximum length, in bytes, of a util‐
618 ity's input line (either standard input or another file), when
619 the utility is described as processing text files. The length
620 includes room for the trailing <newline>.
621 Value: 2 048
622 {_POSIX2_RE_DUP_MAX}
624 Maximum number of repeated occurrences of a regular expression
625 permitted when using the interval notation \{m,n\}; see Chapter
626 9, Regular Expressions.
627 Value: 255
628 {_XOPEN_IOV_MAX}
630 Maximum number of iovec structures that one process has available
631 for use with readv() or writev().
632 Value: 16
633 {_XOPEN_NAME_MAX}
635 Maximum number of bytes in a filename (not including the termi‐
636 nating null of a filename string).
637 Value: 255
638 {_XOPEN_PATH_MAX}
640 Minimum number the implementation will accept as the maximum num‐
641 ber of bytes in a pathname.
642 Value: 1024
643 Numerical Limits
645 The <limits.h> header shall define the following macros and, except for
646 {CHAR_BIT}, {LONG_BIT}, {MB_LEN_MAX}, and {WORD_BIT}, they shall be
647 replaced by expressions that have the same type as would an expression
648 that is an object of the corresponding type converted according to the
649 integer promotions.
650 If the value of an object of type char is treated as a signed integer
652 when used in an expression, the value of {CHAR_MIN} is the same as that
653 of {SCHAR_MIN} and the value of {CHAR_MAX} is the same as that of
654 {SCHAR_MAX}. Otherwise, the value of {CHAR_MIN} is 0 and the value of
655 {CHAR_MAX} is the same as that of {UCHAR_MAX}.
656 {CHAR_BIT}
658 Number of bits in a type char.
659 Value: 8
660 {CHAR_MAX}
662 Maximum value for an object of type char.
663 Value: {UCHAR_MAX} or {SCHAR_MAX}
664 {CHAR_MIN}
666 Minimum value for an object of type char.
667 Value: {SCHAR_MIN} or 0
668 {INT_MAX}
670 Maximum value for an object of type int.
671 Minimum Acceptable Value: 2 147 483 647
672 {INT_MIN}
674 Minimum value for an object of type int.
675 Maximum Acceptable Value: −2 147 483 647
676 {LLONG_MAX}
678 Maximum value for an object of type long long.
679 Minimum Acceptable Value: +9223372036854775807
680 {LLONG_MIN}
682 Minimum value for an object of type long long.
683 Maximum Acceptable Value: −9223372036854775807
684 {LONG_BIT}
686 Number of bits in an object of type long.
687 Minimum Acceptable Value: 32
688 {LONG_MAX}
690 Maximum value for an object of type long.
691 Minimum Acceptable Value: +2 147 483 647
692 {LONG_MIN}
694 Minimum value for an object of type long.
695 Maximum Acceptable Value: −2 147 483 647
696 {MB_LEN_MAX}
698 Maximum number of bytes in a character, for any supported locale.
699 Minimum Acceptable Value: 1
700 {SCHAR_MAX}
702 Maximum value for an object of type signed char.
703 Value: +127
704 {SCHAR_MIN}
706 Minimum value for an object of type signed char.
707 Value: −128
708 {SHRT_MAX}
710 Maximum value for an object of type short.
711 Minimum Acceptable Value: +32 767
712 {SHRT_MIN}
714 Minimum value for an object of type short.
715 Maximum Acceptable Value: −32 767
716 {SSIZE_MAX}
718 Maximum value for an object of type ssize_t.
719 Minimum Acceptable Value: {_POSIX_SSIZE_MAX}
720 {UCHAR_MAX}
722 Maximum value for an object of type unsigned char.
723 Value: 255
724 {UINT_MAX}
726 Maximum value for an object of type unsigned.
727 Minimum Acceptable Value: 4 294 967 295
728 {ULLONG_MAX}
730 Maximum value for an object of type unsigned long long.
731 Minimum Acceptable Value: 18446744073709551615
732 {ULONG_MAX}
734 Maximum value for an object of type unsigned long.
735 Minimum Acceptable Value: 4 294 967 295
736 {USHRT_MAX}
738 Maximum value for an object of type unsigned short.
739 Minimum Acceptable Value: 65 535
740 {WORD_BIT}
742 Number of bits in an object of type int.
743 Minimum Acceptable Value: 32
744 Other Invariant Values
746 The <limits.h> header shall define the following symbolic constants:
747 {NL_ARGMAX}
749 Maximum value of n in conversion specifications using the "%n$"
750 sequence in calls to the printf() and scanf() families of func‐
751 tions.
752 Minimum Acceptable Value: 9
753 {NL_LANGMAX}
755 Maximum number of bytes in a LANG name.
756 Minimum Acceptable Value: 14
757 {NL_MSGMAX}
759 Maximum message number.
760 Minimum Acceptable Value: 32 767
761 {NL_SETMAX}
763 Maximum set number.
764 Minimum Acceptable Value: 255
765 {NL_TEXTMAX}
767 Maximum number of bytes in a message string.
768 Minimum Acceptable Value: {_POSIX2_LINE_MAX}
769 {NZERO}
771 Default process priority.
772 Minimum Acceptable Value: 20
773 The following sections are informative.
775
777 None.
778
780 A request was made to reduce the value of {_POSIX_LINK_MAX} from the
781 value of 8 specified for it in the POSIX.1‐1990 standard to 2. The
782 standard developers decided to deny this request for several reasons:
783 * They wanted to avoid making any changes to the standard that could
785 break conforming applications, and the requested change could have
786 that effect.
787 * The use of multiple hard links to a file cannot always be replaced
789 with use of symbolic links. Symbolic links are semantically differ‐
790 ent from hard links in that they associate a pathname with another
791 pathname rather than a pathname with a file. This has implications
792 for access control, file permanence, and transparency.
793 * The original standard developers had considered the issue of allow‐
795 ing for implementations that did not in general support hard links,
796 and decided that this would reduce consensus on the standard.
797 Systems that support historical versions of the development option of
799 the ISO POSIX‐2 standard retain the name {_POSIX2_RE_DUP_MAX} as an
800 alias for {_POSIX_RE_DUP_MAX}.
801 {PATH_MAX}
803 IEEE PASC Interpretation 1003.1 #15 addressed the inconsistency
804 in the standard with the definition of pathname and the descrip‐
805 tion of {PATH_MAX}, allowing application developers to allocate
806 either {PATH_MAX} or {PATH_MAX}+1 bytes. The inconsistency has
807 been removed by correction to the {PATH_MAX} definition to
808 include the null character. With this change, applications that
809 previously allocated {PATH_MAX} bytes will continue to succeed.
810 {SYMLINK_MAX}
812 This symbol refers to space for data that is stored in the file
813 system, as opposed to {PATH_MAX} which is the length of a name
814 that can be passed to a function. In some existing implementa‐
815 tions, the pathnames pointed to by symbolic links are stored in
816 the inodes of the links, so it is important that {SYMLINK_MAX}
817 not be constrained to be as large as {PATH_MAX}.
818
820 None.
821
823 Chapter 7, Locale, <stdio.h>, <unistd.h>
824 The System Interfaces volume of POSIX.1‐2008, Section 2.2, The Compila‐
826 tion Environment, fpathconf(), sysconf()
827
829 Portions of this text are reprinted and reproduced in electronic form
830 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
831 -- Portable Operating System Interface (POSIX), The Open Group Base
832 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
833 cal and Electronics Engineers, Inc and The Open Group. (This is
834 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
835 event of any discrepancy between this version and the original IEEE and
836 The Open Group Standard, the original IEEE and The Open Group Standard
837 is the referee document. The original Standard can be obtained online
838 at http://www.unix.org/online.html .
839 Any typographical or formatting errors that appear in this page are
841 most likely to have been introduced during the conversion of the source
842 files to man page format. To report such errors, see https://www.ker‐
843 nel.org/doc/man-pages/reporting_bugs.html .
844IEEE/The Open Group 2013 limits.h(0P)