1<unistd.h>(0P) POSIX Programmer's Manual <unistd.h>(0P)
2
6 unistd.h - standard symbolic constants and types
7
9 #include <unistd.h>
10
12 The <unistd.h> header defines miscellaneous symbolic constants and
13 types, and declares miscellaneous functions. The actual values of the
14 constants are unspecified except as shown. The contents of this header
15 are shown below.
16 Version Test Macros
18 The following symbolic constants shall be defined:
19 _POSIX_VERSION
21 Integer value indicating version of IEEE Std 1003.1 (C-language
22 binding) to which the implementation conforms. For implementa‐
23 tions conforming to IEEE Std 1003.1-2001, the value shall be
24 200112L.
25 _POSIX2_VERSION
27 Integer value indicating version of the Shell and Utilities vol‐
28 ume of IEEE Std 1003.1 to which the implementation conforms. For
29 implementations conforming to IEEE Std 1003.1-2001, the value
30 shall be 200112L.
31 The following symbolic constant shall be defined only if the implemen‐
34 tation supports the XSI option; see XSI Conformance .
35 _XOPEN_VERSION
37 Integer value indicating version of the X/Open Portability Guide
39 to which the implementation conforms. The value shall be 600.
40 Constants for Options and Option Groups
43 The following symbolic constants, if defined in <unistd.h>, shall have
44 a value of -1, 0, or greater, unless otherwise specified below. If
45 these are undefined, the fpathconf(), pathconf(), or sysconf() func‐
46 tions can be used to determine whether the option is provided for a
47 particular invocation of the application.
48 If a symbolic constant is defined with the value -1, the option is not
50 supported. Headers, data types, and function interfaces required only
51 for the option need not be supplied. An application that attempts to
52 use anything associated only with the option is considered to be
53 requiring an extension.
54 If a symbolic constant is defined with a value greater than zero, the
56 option shall always be supported when the application is executed. All
57 headers, data types, and functions shall be present and shall operate
58 as specified.
59 If a symbolic constant is defined with the value zero, all headers,
61 data types, and functions shall be present. The application can check
62 at runtime to see whether the option is supported by calling fpath‐
63 conf(), pathconf(), or sysconf() with the indicated name parameter.
64 Unless explicitly specified otherwise, the behavior of functions asso‐
66 ciated with an unsupported option is unspecified, and an application
67 that uses such functions without first checking fpathconf(), path‐
68 conf(), or sysconf() is considered to be requiring an extension.
69 For conformance requirements, refer to Conformance .
71 _POSIX_ADVISORY_INFO
73 The implementation supports the Advisory Information option. If
75 this symbol has a value other than -1 or 0, it shall have the
76 value 200112L.
77 _POSIX_ASYNCHRONOUS_IO
79 The implementation supports the Asynchronous Input and Output
81 option. If this symbol has a value other than -1 or 0, it shall
82 have the value 200112L.
83 _POSIX_BARRIERS
85 The implementation supports the Barriers option. If this symbol
87 has a value other than -1 or 0, it shall have the value 200112L.
88 _POSIX_CHOWN_RESTRICTED
90 The use of chown() and fchown() is restricted to a process with
91 appropriate privileges, and to changing the group ID of a file
92 only to the effective group ID of the process or to one of its
93 supplementary group IDs. This symbol shall always be set to a
94 value other than -1.
95 _POSIX_CLOCK_SELECTION
97 The implementation supports the Clock Selection option. If this
99 symbol has a value other than -1 or 0, it shall have the value
100 200112L.
101 _POSIX_CPUTIME
103 The implementation supports the Process CPU-Time Clocks option.
105 If this symbol has a value other than -1 or 0, it shall have the
106 value 200112L.
107 _POSIX_FSYNC
109 The implementation supports the File Synchronization option. If
111 this symbol has a value other than -1 or 0, it shall have the
112 value 200112L.
113 _POSIX_IPV6
115 The implementation supports the IPv6 option. If this symbol has
116 a value other than -1 or 0, it shall have the value 200112L.
117 _POSIX_JOB_CONTROL
119 The implementation supports job control. This symbol shall
120 always be set to a value greater than zero.
121 _POSIX_MAPPED_FILES
123 The implementation supports the Memory Mapped Files option. If
125 this symbol has a value other than -1 or 0, it shall have the
126 value 200112L.
127 _POSIX_MEMLOCK
129 The implementation supports the Process Memory Locking option.
131 If this symbol has a value other than -1 or 0, it shall have the
132 value 200112L.
133 _POSIX_MEMLOCK_RANGE
135 The implementation supports the Range Memory Locking option. If
137 this symbol has a value other than -1 or 0, it shall have the
138 value 200112L.
139 _POSIX_MEMORY_PROTECTION
141 The implementation supports the Memory Protection option. If
143 this symbol has a value other than -1 or 0, it shall have the
144 value 200112L.
145 _POSIX_MESSAGE_PASSING
147 The implementation supports the Message Passing option. If this
149 symbol has a value other than -1 or 0, it shall have the value
150 200112L.
151 _POSIX_MONOTONIC_CLOCK
153 The implementation supports the Monotonic Clock option. If this
155 symbol has a value other than -1 or 0, it shall have the value
156 200112L.
157 _POSIX_NO_TRUNC
159 Pathname components longer than {NAME_MAX} generate an error.
160 This symbol shall always be set to a value other than -1.
161 _POSIX_PRIORITIZED_IO
163 The implementation supports the Prioritized Input and Output
165 option. If this symbol has a value other than -1 or 0, it shall
166 have the value 200112L.
167 _POSIX_PRIORITY_SCHEDULING
169 The implementation supports the Process Scheduling option. If
171 this symbol has a value other than -1 or 0, it shall have the
172 value 200112L.
173 _POSIX_RAW_SOCKETS
175 The implementation supports the Raw Sockets option. If this sym‐
177 bol has a value other than -1 or 0, it shall have the value
178 200112L.
179 _POSIX_READER_WRITER_LOCKS
181 The implementation supports the Read-Write Locks option. This is
183 always set to a value greater than zero if the Threads option is
184 supported. If this symbol has a value other than -1 or 0, it
185 shall have the value 200112L.
186 _POSIX_REALTIME_SIGNALS
188 The implementation supports the Realtime Signals Extension
190 option. If this symbol has a value other than -1 or 0, it shall
191 have the value 200112L.
192 _POSIX_REGEXP
194 The implementation supports the Regular Expression Handling
195 option. This symbol shall always be set to a value greater than
196 zero.
197 _POSIX_SAVED_IDS
199 Each process has a saved set-user-ID and a saved set-group-ID.
200 This symbol shall always be set to a value greater than zero.
201 _POSIX_SEMAPHORES
203 The implementation supports the Semaphores option. If this sym‐
205 bol has a value other than -1 or 0, it shall have the value
206 200112L.
207 _POSIX_SHARED_MEMORY_OBJECTS
209 The implementation supports the Shared Memory Objects option. If
211 this symbol has a value other than -1 or 0, it shall have the
212 value 200112L.
213 _POSIX_SHELL
215 The implementation supports the POSIX shell. This symbol shall
216 always be set to a value greater than zero.
217 _POSIX_SPAWN
219 The implementation supports the Spawn option. If this symbol has
221 a value other than -1 or 0, it shall have the value 200112L.
222 _POSIX_SPIN_LOCKS
224 The implementation supports the Spin Locks option. If this sym‐
226 bol has a value other than -1 or 0, it shall have the value
227 200112L.
228 _POSIX_SPORADIC_SERVER
230 The implementation supports the Process Sporadic Server option.
232 If this symbol has a value other than -1 or 0, it shall have the
233 value 200112L.
234 _POSIX_SYNCHRONIZED_IO
236 The implementation supports the Synchronized Input and Output
238 option. If this symbol has a value other than -1 or 0, it shall
239 have the value 200112L.
240 _POSIX_THREAD_ATTR_STACKADDR
242 The implementation supports the Thread Stack Address Attribute
244 option. If this symbol has a value other than -1 or 0, it shall
245 have the value 200112L.
246 _POSIX_THREAD_ATTR_STACKSIZE
248 The implementation supports the Thread Stack Size Attribute
250 option. If this symbol has a value other than -1 or 0, it shall
251 have the value 200112L.
252 _POSIX_THREAD_CPUTIME
254 The implementation supports the Thread CPU-Time Clocks option.
256 If this symbol has a value other than -1 or 0, it shall have the
257 value 200112L.
258 _POSIX_THREAD_PRIO_INHERIT
260 The implementation supports the Thread Priority Inheritance
262 option. If this symbol has a value other than -1 or 0, it shall
263 have the value 200112L.
264 _POSIX_THREAD_PRIO_PROTECT
266 The implementation supports the Thread Priority Protection
268 option. If this symbol has a value other than -1 or 0, it shall
269 have the value 200112L.
270 _POSIX_THREAD_PRIORITY_SCHEDULING
272 The implementation supports the Thread Execution Scheduling
274 option. If this symbol has a value other than -1 or 0, it shall
275 have the value 200112L.
276 _POSIX_THREAD_PROCESS_SHARED
278 The implementation supports the Thread Process-Shared Synchro‐
280 nization option. If this symbol has a value other than -1 or 0,
281 it shall have the value 200112L.
282 _POSIX_THREAD_SAFE_FUNCTIONS
284 The implementation supports the Thread-Safe Functions option. If
286 this symbol has a value other than -1 or 0, it shall have the
287 value 200112L.
288 _POSIX_THREAD_SPORADIC_SERVER
290 The implementation supports the Thread Sporadic Server option.
292 If this symbol has a value other than -1 or 0, it shall have the
293 value 200112L.
294 _POSIX_THREADS
296 The implementation supports the Threads option. If this symbol
298 has a value other than -1 or 0, it shall have the value 200112L.
299 _POSIX_TIMEOUTS
301 The implementation supports the Timeouts option. If this symbol
303 has a value other than -1 or 0, it shall have the value 200112L.
304 _POSIX_TIMERS
306 The implementation supports the Timers option. If this symbol
308 has a value other than -1 or 0, it shall have the value 200112L.
309 _POSIX_TRACE
311 The implementation supports the Trace option. If this symbol has
313 a value other than -1 or 0, it shall have the value 200112L.
314 _POSIX_TRACE_EVENT_FILTER
316 The implementation supports the Trace Event Filter option. If
318 this symbol has a value other than -1 or 0, it shall have the
319 value 200112L.
320 _POSIX_TRACE_INHERIT
322 The implementation supports the Trace Inherit option. If this
324 symbol has a value other than -1 or 0, it shall have the value
325 200112L.
326 _POSIX_TRACE_LOG
328 The implementation supports the Trace Log option. If this symbol
330 has a value other than -1 or 0, it shall have the value 200112L.
331 _POSIX_TYPED_MEMORY_OBJECTS
333 The implementation supports the Typed Memory Objects option. If
335 this symbol has a value other than -1 or 0, it shall have the
336 value 200112L.
337 _POSIX_VDISABLE
339 This symbol shall be defined to be the value of a character that
340 shall disable terminal special character handling as described
341 in <termios.h> . This symbol shall always be set to a value
342 other than -1.
343 _POSIX2_C_BIND
345 The implementation supports the C-Language Binding option. This
346 symbol shall always have the value 200112L.
347 _POSIX2_C_DEV
349 The implementation supports the C-Language Development Utilities
351 option. If this symbol has a value other than -1 or 0, it shall
352 have the value 200112L.
353 _POSIX2_CHAR_TERM
355 The implementation supports at least one terminal type.
356 _POSIX2_FORT_DEV
358 The implementation supports the FORTRAN Development Utilities
360 option. If this symbol has a value other than -1 or 0, it shall
361 have the value 200112L.
362 _POSIX2_FORT_RUN
364 The implementation supports the FORTRAN Runtime Utilities
366 option. If this symbol has a value other than -1 or 0, it shall
367 have the value 200112L.
368 _POSIX2_LOCALEDEF
370 The implementation supports the creation of locales by the
371 localedef utility. If this symbol has a value other than -1 or
372 0, it shall have the value 200112L.
373 _POSIX2_PBS
375 The implementation supports the Batch Environment Services and
377 Utilities option. If this symbol has a value other than -1 or 0,
378 it shall have the value 200112L.
379 _POSIX2_PBS_ACCOUNTING
381 The implementation supports the Batch Accounting option. If this
383 symbol has a value other than -1 or 0, it shall have the value
384 200112L.
385 _POSIX2_PBS_CHECKPOINT
387 The implementation supports the Batch Checkpoint/Restart option.
389 If this symbol has a value other than -1 or 0, it shall have the
390 value 200112L.
391 _POSIX2_PBS_LOCATE
393 The implementation supports the Locate Batch Job Request option.
395 If this symbol has a value other than -1 or 0, it shall have the
396 value 200112L.
397 _POSIX2_PBS_MESSAGE
399 The implementation supports the Batch Job Message Request
401 option. If this symbol has a value other than -1 or 0, it shall
402 have the value 200112L.
403 _POSIX2_PBS_TRACK
405 The implementation supports the Track Batch Job Request option.
407 If this symbol has a value other than -1 or 0, it shall have the
408 value 200112L.
409 _POSIX2_SW_DEV
411 The implementation supports the Software Development Utilities
413 option. If this symbol has a value other than -1 or 0, it shall
414 have the value 200112L.
415 _POSIX2_UPE
417 The implementation supports the User Portability Utilities
419 option. If this symbol has a value other than -1 or 0, it shall
420 have the value 200112L.
421 _V6_ILP32_OFF32
423 The implementation provides a C-language compilation environment
424 with 32-bit int, long, pointer, and off_t types.
425 _V6_ILP32_OFFBIG
427 The implementation provides a C-language compilation environment
428 with 32-bit int, long, and pointer types and an off_t type using
429 at least 64 bits.
430 _V6_LP64_OFF64
432 The implementation provides a C-language compilation environment
433 with 32-bit int and 64-bit long, pointer, and off_t types.
434 _V6_LPBIG_OFFBIG
436 The implementation provides a C-language compilation environment
437 with an int type using at least 32 bits and long, pointer, and
438 off_t types using at least 64 bits.
439 _XBS5_ILP32_OFF32 (LEGACY)
441 The implementation provides a C-language compilation environment
443 with 32-bit int, long, pointer, and off_t types.
444 _XBS5_ILP32_OFFBIG (LEGACY)
446 The implementation provides a C-language compilation environment
448 with 32-bit int, long, and pointer types and an off_t type using
449 at least 64 bits.
450 _XBS5_LP64_OFF64 (LEGACY)
452 The implementation provides a C-language compilation environment
454 with 32-bit int and 64-bit long, pointer, and off_t types.
455 _XBS5_LPBIG_OFFBIG (LEGACY)
457 The implementation provides a C-language compilation environment
459 with an int type using at least 32 bits and long, pointer, and
460 off_t types using at least 64 bits.
461 _XOPEN_CRYPT
463 The implementation supports the X/Open Encryption Option Group.
465 _XOPEN_ENH_I18N
467 The implementation supports the Issue 4, Version 2 Enhanced
468 Internationalization Option Group. This symbol shall always be
469 set to a value other than -1.
470 _XOPEN_LEGACY
472 The implementation supports the Legacy Option Group.
473 _XOPEN_REALTIME
475 The implementation supports the X/Open Realtime Option Group.
476 _XOPEN_REALTIME_THREADS
478 The implementation supports the X/Open Realtime Threads Option
479 Group.
480 _XOPEN_SHM
482 The implementation supports the Issue 4, Version 2 Shared Memory
483 Option Group. This symbol shall always be set to a value other
484 than -1.
485 _XOPEN_STREAMS
487 The implementation supports the XSI STREAMS Option Group.
488 _XOPEN_UNIX
490 The implementation supports the XSI extension.
492 Execution-Time Symbolic Constants
495 If any of the following constants are not defined in the <unistd.h>
496 header, the value shall vary depending on the file to which it is
497 applied.
498 If any of the following constants are defined to have value -1 in the
500 <unistd.h> header, the implementation shall not provide the option on
501 any file; if any are defined to have a value other than -1 in the
502 <unistd.h> header, the implementation shall provide the option on all
503 applicable files.
504 All of the following constants, whether defined in <unistd.h> or not,
506 may be queried with respect to a specific file using the pathconf() or
507 fpathconf() functions:
508 _POSIX_ASYNC_IO
510 Asynchronous input or output operations may be performed for the
511 associated file.
512 _POSIX_PRIO_IO
514 Prioritized input or output operations may be performed for the
515 associated file.
516 _POSIX_SYNC_IO
518 Synchronized input or output operations may be performed for the
519 associated file.
520 Constants for Functions
523 The following symbolic constant shall be defined:
524 NULL Null pointer
526 The following symbolic constants shall be defined for the access()
529 function:
530 F_OK Test for existence of file.
532 R_OK Test for read permission.
534 W_OK Test for write permission.
536 X_OK Test for execute (search) permission.
538 The constants F_OK, R_OK, W_OK, and X_OK and the expressions R_OK|W_OK,
541 R_OK|X_OK, and R_OK|W_OK|X_OK shall all have distinct values.
542 The following symbolic constants shall be defined for the confstr()
544 function:
545 _CS_PATH
547 This is the value for the PATH environment variable that finds
548 all standard utilities.
549 _CS_POSIX_V6_ILP32_OFF32_CFLAGS
551 If sysconf(_SC_V6_ILP32_OFF32) returns -1, the meaning of this
552 value is unspecified. Otherwise, this value is the set of ini‐
553 tial options to be given to the c99 utility to build an applica‐
554 tion using a programming model with 32-bit int, long, pointer,
555 and off_t types.
556 _CS_POSIX_V6_ILP32_OFF32_LDFLAGS
558 If sysconf(_SC_V6_ILP32_OFF32) returns -1, the meaning of this
559 value is unspecified. Otherwise, this value is the set of final
560 options to be given to the c99 utility to build an application
561 using a programming model with 32-bit int, long, pointer, and
562 off_t types.
563 _CS_POSIX_V6_ILP32_OFF32_LIBS
565 If sysconf(_SC_V6_ILP32_OFF32) returns -1, the meaning of this
566 value is unspecified. Otherwise, this value is the set of
567 libraries to be given to the c99 utility to build an application
568 using a programming model with 32-bit int, long, pointer, and
569 off_t types.
570 _CS_POSIX_V6_ILP32_OFFBIG_CFLAGS
572 If sysconf(_SC_V6_ILP32_OFFBIG) returns -1, the meaning of this
573 value is unspecified. Otherwise, this value is the set of ini‐
574 tial options to be given to the c99 utility to build an applica‐
575 tion using a programming model with 32-bit int, long, and
576 pointer types, and an off_t type using at least 64 bits.
577 _CS_POSIX_V6_ILP32_OFFBIG_LDFLAGS
579 If sysconf(_SC_V6_ILP32_OFFBIG) returns -1, the meaning of this
580 value is unspecified. Otherwise, this value is the set of final
581 options to be given to the c99 utility to build an application
582 using a programming model with 32-bit int, long, and pointer
583 types, and an off_t type using at least 64 bits.
584 _CS_POSIX_V6_ILP32_OFFBIG_LIBS
586 If sysconf(_SC_V6_ILP32_OFFBIG) returns -1, the meaning of this
587 value is unspecified. Otherwise, this value is the set of
588 libraries to be given to the c99 utility to build an application
589 using a programming model with 32-bit int, long, and pointer
590 types, and an off_t type using at least 64 bits.
591 _CS_POSIX_V6_LP64_OFF64_CFLAGS
593 If sysconf(_SC_V6_LP64_OFF64) returns -1, the meaning of this
594 value is unspecified. Otherwise, this value is the set of ini‐
595 tial options to be given to the c99 utility to build an applica‐
596 tion using a programming model with 32-bit int and 64-bit long,
597 pointer, and off_t types.
598 _CS_POSIX_V6_LP64_OFF64_LDFLAGS
600 If sysconf(_SC_V6_LP64_OFF64) returns -1, the meaning of this
601 value is unspecified. Otherwise, this value is the set of final
602 options to be given to the c99 utility to build an application
603 using a programming model with 32-bit int and 64-bit long,
604 pointer, and off_t types.
605 _CS_POSIX_V6_LP64_OFF64_LIBS
607 If sysconf(_SC_V6_LP64_OFF64) returns -1, the meaning of this
608 value is unspecified. Otherwise, this value is the set of
609 libraries to be given to the c99 utility to build an application
610 using a programming model with 32-bit int and 64-bit long,
611 pointer, and off_t types.
612 _CS_POSIX_V6_LPBIG_OFFBIG_CFLAGS
614 If sysconf(_SC_V6_LPBIG_OFFBIG) returns -1, the meaning of this
615 value is unspecified. Otherwise, this value is the set of ini‐
616 tial options to be given to the c99 utility to build an applica‐
617 tion using a programming model with an int type using at least
618 32 bits and long, pointer, and off_t types using at least 64
619 bits.
620 _CS_POSIX_V6_LPBIG_OFFBIG_LDFLAGS
622 If sysconf(_SC_V6_LPBIG_OFFBIG) returns -1, the meaning of this
623 value is unspecified. Otherwise, this value is the set of final
624 options to be given to the c99 utility to build an application
625 using a programming model with an int type using at least 32
626 bits and long, pointer, and off_t types using at least 64 bits.
627 _CS_POSIX_V6_LPBIG_OFFBIG_LIBS
629 If sysconf(_SC_V6_LPBIG_OFFBIG) returns -1, the meaning of this
630 value is unspecified. Otherwise, this value is the set of
631 libraries to be given to the c99 utility to build an application
632 using a programming model with an int type using at least 32
633 bits and long, pointer, and off_t types using at least 64 bits.
634 _CS_POSIX_V6_WIDTH_RESTRICTED_ENVS
636 This value is a <newline>-separated list of names of programming
637 environments supported by the implementation in which the widths
638 of the blksize_t, cc_t, mode_t, nfds_t, pid_t, ptrdiff_t,
639 size_t, speed_t, ssize_t, suseconds_t, tcflag_t, useconds_t,
640 wchar_t, and wint_t types are no greater than the width of type
641 long.
642 The following symbolic constants are reserved for compatibility with
645 Issue 5:
646 _CS_XBS5_ILP32_OFF32_CFLAGS (LEGACY)
648 _CS_XBS5_ILP32_OFF32_LDFLAGS (LEGACY)
649 _CS_XBS5_ILP32_OFF32_LIBS (LEGACY)
650 _CS_XBS5_ILP32_OFF32_LINTFLAGS (LEGACY)
651 _CS_XBS5_ILP32_OFFBIG_CFLAGS (LEGACY)
652 _CS_XBS5_ILP32_OFFBIG_LDFLAGS (LEGACY)
653 _CS_XBS5_ILP32_OFFBIG_LIBS (LEGACY)
654 _CS_XBS5_ILP32_OFFBIG_LINTFLAGS (LEGACY)
655 _CS_XBS5_LP64_OFF64_CFLAGS (LEGACY)
656 _CS_XBS5_LP64_OFF64_LDFLAGS (LEGACY)
657 _CS_XBS5_LP64_OFF64_LIBS (LEGACY)
658 _CS_XBS5_LP64_OFF64_LINTFLAGS (LEGACY)
659 _CS_XBS5_LPBIG_OFFBIG_CFLAGS (LEGACY)
660 _CS_XBS5_LPBIG_OFFBIG_LDFLAGS (LEGACY)
661 _CS_XBS5_LPBIG_OFFBIG_LIBS (LEGACY)
662 _CS_XBS5_LPBIG_OFFBIG_LINTFLAGS (LEGACY)
663 The following symbolic constants shall be defined for the lseek() and
666 fcntl() functions and shall have distinct values:
667 SEEK_CUR
669 Set file offset to current plus offset.
670 SEEK_END
672 Set file offset to EOF plus offset.
673 SEEK_SET
675 Set file offset to offset.
676 The following symbolic constants shall be defined as possible values
679 for the function argument to the lockf() function:
680 F_LOCK Lock a section for exclusive use.
682 F_TEST Test section for locks by other processes.
684 F_TLOCK
686 Test and lock a section for exclusive use.
687 F_ULOCK
689 Unlock locked sections.
690 The following symbolic constants shall be defined for pathconf():
693 _PC_ALLOC_SIZE_MIN
695 _PC_ASYNC_IO
696 _PC_CHOWN_RESTRICTED
697 _PC_FILESIZEBITS
698 _PC_LINK_MAX
699 _PC_MAX_CANON
700 _PC_MAX_INPUT
701 _PC_NAME_MAX
702 _PC_NO_TRUNC
703 _PC_PATH_MAX
704 _PC_PIPE_BUF
705 _PC_PRIO_IO
706 _PC_REC_INCR_XFER_SIZE
707 _PC_REC_MIN_XFER_SIZE
708 _PC_REC_XFER_ALIGN
709 _PC_SYMLINK_MAX
710 _PC_SYNC_IO
711 _PC_VDISABLE
712 The following symbolic constants shall be defined for sysconf():
714 _SC_2_C_BIND
716 _SC_2_C_DEV
717 _SC_2_C_VERSION
718 _SC_2_CHAR_TERM
719 _SC_2_FORT_DEV
720 _SC_2_FORT_RUN
721 _SC_2_LOCALEDEF
722 _SC_2_PBS
723 _SC_2_PBS_ACCOUNTING
724 _SC_2_PBS_CHECKPOINT
725 _SC_2_PBS_LOCATE
726 _SC_2_PBS_MESSAGE
727 _SC_2_PBS_TRACK
728 _SC_2_SW_DEV
729 _SC_2_UPE
730 _SC_2_VERSION
731 _SC_ADVISORY_INFO
732 _SC_ARG_MAX
733 _SC_AIO_LISTIO_MAX
734 _SC_AIO_MAX
735 _SC_AIO_PRIO_DELTA_MAX
736 _SC_ASYNCHRONOUS_IO
737 _SC_ATEXIT_MAX
738 _SC_BARRIERS
739 _SC_BC_BASE_MAX
740 _SC_BC_DIM_MAX
741 _SC_BC_SCALE_MAX
742 _SC_BC_STRING_MAX
743 _SC_CHILD_MAX
744 _SC_CLK_TCK
745 _SC_CLOCK_SELECTION
746 _SC_COLL_WEIGHTS_MAX
747 _SC_CPUTIME
748 _SC_DELAYTIMER_MAX
749 _SC_EXPR_NEST_MAX
750 _SC_FILE_LOCKING
751 _SC_FSYNC
752 _SC_GETGR_R_SIZE_MAX
753 _SC_GETPW_R_SIZE_MAX
754 _SC_HOST_NAME_MAX
755 _SC_IOV_MAX
756 _SC_IPV6
757 _SC_JOB_CONTROL
758 _SC_LINE_MAX
759 _SC_LOGIN_NAME_MAX
760 _SC_MAPPED_FILES
761 _SC_MEMLOCK
762 _SC_MEMLOCK_RANGE
763 _SC_MEMORY_PROTECTION
764 _SC_MESSAGE_PASSING
765 _SC_MONOTONIC_CLOCK
766 _SC_MQ_OPEN_MAX
767 _SC_MQ_PRIO_MAX
768 _SC_NGROUPS_MAX
769 _SC_OPEN_MAX
770 _SC_PAGE_SIZE
771 _SC_PAGESIZE
772 _SC_PRIORITIZED_IO
773 _SC_PRIORITY_SCHEDULING
774 _SC_RAW_SOCKETS
775 _SC_RE_DUP_MAX
776 _SC_READER_WRITER_LOCKS
777 _SC_REALTIME_SIGNALS
778 _SC_REGEXP
779 _SC_RTSIG_MAX
780 _SC_SAVED_IDS
781 _SC_SEMAPHORES
782 _SC_SEM_NSEMS_MAX
783 _SC_SEM_VALUE_MAX
784 _SC_SHARED_MEMORY_OBJECTS
785 _SC_SHELL
786 _SC_SIGQUEUE_MAX
787 _SC_SPAWN
788 _SC_SPIN_LOCKS
789 _SC_SPORADIC_SERVER
790 _SC_STREAM_MAX
791 _SC_SYMLOOP_MAX
792 _SC_SYNCHRONIZED_IO
793 _SC_THREAD_ATTR_STACKADDR
794 _SC_THREAD_ATTR_STACKSIZE
795 _SC_THREAD_CPUTIME
796 _SC_THREAD_DESTRUCTOR_ITERATIONS
797 _SC_THREAD_KEYS_MAX
798 _SC_THREAD_PRIO_INHERIT
799 _SC_THREAD_PRIO_PROTECT
800 _SC_THREAD_PRIORITY_SCHEDULING
801 _SC_THREAD_PROCESS_SHARED
802 _SC_THREAD_SAFE_FUNCTIONS
803 _SC_THREAD_SPORADIC_SERVER
804 _SC_THREAD_STACK_MIN
805 _SC_THREAD_THREADS_MAX
806 _SC_TIMEOUTS
807 _SC_THREADS
808 _SC_TIMER_MAX
809 _SC_TIMERS
810 _SC_TRACE
811 _SC_TRACE_EVENT_FILTER
812 _SC_TRACE_INHERIT
813 _SC_TRACE_LOG
814 _SC_TTY_NAME_MAX
815 _SC_TYPED_MEMORY_OBJECTS
816 _SC_TZNAME_MAX
817 _SC_V6_ILP32_OFF32
818 _SC_V6_ILP32_OFFBIG
819 _SC_V6_LP64_OFF64
820 _SC_V6_LPBIG_OFFBIG
821 _SC_VERSION
822 _SC_XBS5_ILP32_OFF32 (LEGACY)
823 _SC_XBS5_ILP32_OFFBIG (LEGACY)
824 _SC_XBS5_LP64_OFF64 (LEGACY)
825 _SC_XBS5_LPBIG_OFFBIG (LEGACY)
826 _SC_XOPEN_CRYPT
827 _SC_XOPEN_ENH_I18N
828 _SC_XOPEN_LEGACY
829 _SC_XOPEN_REALTIME
830 _SC_XOPEN_REALTIME_THREADS
831 _SC_XOPEN_SHM
832 _SC_XOPEN_STREAMS
833 _SC_XOPEN_UNIX
834 _SC_XOPEN_VERSION
835 _SC_XOPEN_XCU_VERSION
836 The two constants _SC_PAGESIZE and _SC_PAGE_SIZE may be defined to have
838 the same value.
839 The following symbolic constants shall be defined for file streams:
841 STDERR_FILENO
843 File number of stderr; 2.
844 STDIN_FILENO
846 File number of stdin; 0.
847 STDOUT_FILENO
849 File number of stdout; 1.
850 Type Definitions
853 The size_t, ssize_t, uid_t, gid_t, off_t, pid_t, and useconds_t types
854 shall be defined as described in <sys/types.h>.
855 The intptr_t type shall be defined as described in <inttypes.h>.
857 Declarations
859 The following shall be declared as functions and may also be defined as
860 macros. Function prototypes shall be provided.
861 int access(const char *, int);
864 unsigned alarm(unsigned);
865 int chdir(const char *);
866 int chown(const char *, uid_t, gid_t);
867 int close(int);
868 size_t confstr(int, char *, size_t);
869 char *crypt(const char *, const char *);
873 char *ctermid(char *);
874 int dup(int);
876 int dup2(int, int);
879 void encrypt(char[64], int);
881 int execl(const char *, const char *, ...);
883 int execle(const char *, const char *, ...);
884 int execlp(const char *, const char *, ...);
885 int execv(const char *, char *const []);
886 int execve(const char *, char *const [], char *const []);
887 int execvp(const char *, char *const []);
888 void _exit(int);
889 int fchown(int, uid_t, gid_t);
890 int fchdir(int);
892 int fdatasync(int);
895 pid_t fork(void);
897 long fpathconf(int, int);
898 int fsync(int);
900 int ftruncate(int, off_t);
902 char *getcwd(char *, size_t);
903 gid_t getegid(void);
904 uid_t geteuid(void);
905 gid_t getgid(void);
906 int getgroups(int, gid_t []);
907 long gethostid(void);
909 int gethostname(char *, size_t);
911 char *getlogin(void);
912 int getlogin_r(char *, size_t);
913 int getopt(int, char * const [], const char *);
914 pid_t getpgid(pid_t);
916 pid_t getpgrp(void);
918 pid_t getpid(void);
919 pid_t getppid(void);
920 pid_t getsid(pid_t);
922 uid_t getuid(void);
924 char *getwd(char *); (LEGACY )
926 int isatty(int);
928 int lchown(const char *, uid_t, gid_t);
930 int link(const char *, const char *);
932 int lockf(int, int, off_t);
934 off_t lseek(int, off_t, int);
936 int nice(int);
938 long pathconf(const char *, int);
940 int pause(void);
941 int pipe(int [2]);
942 ssize_t pread(int, void *, size_t, off_t);
944 ssize_t pwrite(int, const void *, size_t, off_t);
945 ssize_t read(int, void *, size_t);
947 ssize_t readlink(const char *restrict, char *restrict, size_t);
948 int rmdir(const char *);
949 int setegid(gid_t);
950 int seteuid(uid_t);
951 int setgid(gid_t);
952 int setpgid(pid_t, pid_t);
955 pid_t setpgrp(void);
957 int setregid(gid_t, gid_t);
958 int setreuid(uid_t, uid_t);
959 pid_t setsid(void);
961 int setuid(uid_t);
962 unsigned sleep(unsigned);
963 void swab(const void *restrict, void *restrict, ssize_t);
965 int symlink(const char *, const char *);
966 void sync(void);
967 long sysconf(int);
969 pid_t tcgetpgrp(int);
970 int tcsetpgrp(int, pid_t);
971 int truncate(const char *, off_t);
973 char *ttyname(int);
975 int ttyname_r(int, char *, size_t);
976 useconds_t ualarm(useconds_t, useconds_t);
978 int unlink(const char *);
980 int usleep(useconds_t);
982 pid_t vfork(void);
983 ssize_t write(int, const void *, size_t);
985 Implementations may also include the pthread_atfork() prototype as
987 defined in <pthread.h> .
988 The following external variables shall be declared:
990 extern char *optarg;
993 extern int optind, opterr, optopt;
994 The following sections are informative.
996
998 IEEE Std 1003.1-2001 only describes the behavior of systems that claim
999 conformance to it. However, application developers who want to write
1000 applications that adapt to other versions of IEEE Std 1003.1 (or to
1001 systems that do not conform to any POSIX standard) may find it useful
1002 to code them so as to conditionally compile different code depending on
1003 the value of _POSIX_VERSION, for example:
1004 #if _POSIX_VERSION >= 200112L
1007 /* Use the newer function that copes with large files. */
1008 off_t pos=ftello(fp);
1009 #else
1010 /* Either this is an old version of POSIX, or _POSIX_VERSION is
1011 not even defined, so use the traditional function. */
1012 long pos=ftell(fp);
1013 #endif
1014 Earlier versions of IEEE Std 1003.1 and of the Single UNIX Specifica‐
1016 tion can be identified by the following macros:
1017 POSIX.1-1988 standard
1019 _POSIX_VERSION==198808L
1020 POSIX.1-1990 standard
1022 _POSIX_VERSION==199009L
1023 ISO POSIX-1:1996 standard
1025 _POSIX_VERSION==199506L
1026 Single UNIX Specification, Version 1
1028 _XOPEN_UNIX and _XOPEN_VERSION==4
1029 Single UNIX Specification, Version 2
1031 _XOPEN_UNIX and _XOPEN_VERSION==500
1032 IEEE Std 1003.1-2001 does not make any attempt to define application
1035 binary interaction with the underlying operating system. However,
1036 application developers may find it useful to query _SC_VERSION at run‐
1037 time via sysconf() to determine whether the current version of the
1038 operating system supports the necessary functionality as in the follow‐
1039 ing program fragment:
1040 if (sysconf(_SC_VERSION) < 200112L) {
1043 fprintf(stderr, "POSIX.1-2001 system required, terminating \n");
1044 exit(1);
1045 }
1046 New applications should not use _XOPEN_SHM or _XOPEN_ENH_I18N.
1048
1050 As IEEE Std 1003.1-2001 evolved, certain options became sufficiently
1051 standardized that it was concluded that simply requiring one of the
1052 option choices was simpler than retaining the option. However, for
1053 backwards-compatibility, the option flags (with required constant val‐
1054 ues) are retained.
1055 Version Test Macros
1057 The standard developers considered altering the definition of
1058 _POSIX_VERSION and removing _SC_VERSION from the specification of
1059 sysconf() since the utility to an application was deemed by some to be
1060 minimal, and since the implementation of the functionality is poten‐
1061 tially problematic. However, they recognized that support for existing
1062 application binaries is a concern to manufacturers, application devel‐
1063 opers, and the users of implementations conforming to
1064 IEEE Std 1003.1-2001.
1065 While the example using _SC_VERSION in the APPLICATION USAGE section
1067 does not provide the greatest degree of imaginable utility to the
1068 application developer or user, it is arguably better than a core file
1069 or some other equally obscure result. (It is also possible for imple‐
1070 mentations to encode and recognize application binaries compiled in
1071 various POSIX.1-conforming environments, and modify the semantics of
1072 the underlying system to conform to the expectations of the applica‐
1073 tion.) For the reasons outlined in the preceding paragraphs and in the
1074 APPLICATION USAGE section, the standard developers elected to retain
1075 the _POSIX_VERSION and _SC_VERSION functionality.
1076 Compile-Time Symbolic Constants for System-Wide Options
1078 IEEE Std 1003.1-2001 now includes support in certain areas for the
1079 newly adopted policy governing options and stubs.
1080 This policy provides flexibility for implementations in how they sup‐
1082 port options. It also specifies how conforming applications can adapt
1083 to different implementations that support different sets of options. It
1084 allows the following:
1085 1. If an implementation has no interest in supporting an option, it
1087 does not have to provide anything associated with that option
1088 beyond the announcement that it does not support it.
1089 2. An implementation can support a partial or incompatible version of
1091 an option (as a non-standard extension) as long as it does not
1092 claim to support the option.
1093 3. An application can determine whether the option is supported. A
1095 strictly conforming application must check this announcement mecha‐
1096 nism before first using anything associated with the option.
1097 There is an important implication of this policy. IEEE Std 1003.1-2001
1099 cannot dictate the behavior of interfaces associated with an option
1100 when the implementation does not claim to support the option. In par‐
1101 ticular, it cannot require that a function associated with an unsup‐
1102 ported option will fail if it does not perform as specified. However,
1103 this policy does not prevent a standard from requiring certain func‐
1104 tions to always be present, but that they shall always fail on some
1105 implementations. The setpgid() function in the POSIX.1-1990 standard,
1106 for example, is considered appropriate.
1107 The POSIX standards include various options, and the C-language binding
1109 support for an option implies that the implementation must supply data
1110 types and function interfaces. An application must be able to discover
1111 whether the implementation supports each option.
1112 Any application must consider the following three cases for each
1114 option:
1115 1. Option never supported.
1117 The implementation advertises at compile time that the option will
1119 never be supported. In this case, it is not necessary for the implemen‐
1120 tation to supply any of the data types or function interfaces that are
1121 provided only as part of the option. The implementation might provide
1122 data types and functions that are similar to those defined by
1123 IEEE Std 1003.1-2001, but there is no guarantee for any particular
1124 behavior.
1125 2. Option always supported.
1127 The implementation advertises at compile time that the option will
1129 always be supported. In this case, all data types and function inter‐
1130 faces shall be available and shall operate as specified.
1131 3. Option might or might not be supported.
1133 Some implementations might not provide a mechanism to specify support
1135 of options at compile time. In addition, the implementation might be
1136 unable or unwilling to specify support or non-support at compile time.
1137 In either case, any application that might use the option at runtime
1138 must be able to compile and execute. The implementation must provide,
1139 at compile time, all data types and function interfaces that are neces‐
1140 sary to allow this. In this situation, there must be a mechanism that
1141 allows the application to query, at runtime, whether the option is sup‐
1142 ported. If the application attempts to use the option when it is not
1143 supported, the result is unspecified unless explicitly specified other‐
1144 wise in IEEE Std 1003.1-2001.
1145
1147 None.
1148
1150 <inttypes.h>, <limits.h>, <sys/socket.h>, <sys/types.h>, <termios.h>,
1151 <wctype.h>, the System Interfaces volume of IEEE Std 1003.1-2001,
1152 access(), alarm(), chdir(), chown(), close(), crypt(), ctermid(),
1153 dup(), encrypt(), environ, exec, exit(), fchdir(), fchown(), fcntl(),
1154 fork(), fpathconf(), fsync(), ftruncate(), getcwd(), getegid(),
1155 geteuid(), getgid(), getgroups(), gethostid(), gethostname(), getlo‐
1156 gin(), getpgid(), getpgrp(), getpid(), getppid(), getsid(), getuid(),
1157 isatty(), lchown(), link(), lockf(), lseek(), nice(), pathconf(),
1158 pause(), pipe(), read(), readlink(), rmdir(), setgid(), setpgid(),
1159 setpgrp(), setregid(), setreuid(), setsid(), setuid(), sleep(), swab(),
1160 symlink(), sync(), sysconf(), tcgetpgrp(), tcsetpgrp(), truncate(),
1161 ttyname(), ualarm(), unlink(), usleep(), vfork(), write()
1162
1164 Portions of this text are reprinted and reproduced in electronic form
1165 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
1166 -- Portable Operating System Interface (POSIX), The Open Group Base
1167 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
1168 Electrical and Electronics Engineers, Inc and The Open Group. In the
1169 event of any discrepancy between this version and the original IEEE and
1170 The Open Group Standard, the original IEEE and The Open Group Standard
1171 is the referee document. The original Standard can be obtained online
1172 at http://www.opengroup.org/unix/online.html .
1173IEEE/The Open Group 2003 <unistd.h>(0P)