1sysconf(3C) Standard C Library Functions sysconf(3C)
2
6 sysconf - get configurable system variables
7
9 #include <unistd.h>
10 long sysconf(int name);
12
15 The sysconf() function provides a method for an application to deter‐
16 mine the current value of a configurable system limit or option (vari‐
17 able).
18 The name argument represents the system variable to be queried. The
21 following table lists the minimal set of system variables from <lim‐
22 its.h> and <unistd.h> that can be returned by sysconf() and the sym‐
23 bolic constants defined in <unistd.h> that are the corresponding values
24 used for name on the SPARC and x86 platforms.
25 Name Return Value Meaning
27 _______________________________________________________________________
28 _SC_2_C_BIND _POSIX2_C_BIND Supports the C lang-
29 uage binding option
30 _SC_2_C_DEV _POSIX2_C_DEV Supports the C lang-
31 uage development
32 utilities option
33 _SC_2_C_VERSION _POSIX2_C_VERSION Integer value
34 indicates version
35 of ISO POSIX-2
36 standard (Commands)
37 _SC_2_CHAR_TERM _POSIX2_CHAR_TERM Supports at least
38 one terminal
39 _SC_2_FORT_DEV _POSIX2_FORT_DEV Supports FORTRAN
40 Development
41 Utilities Option
42 _SC_2_FORT_RUN _POSIX2_FORT_RUN Supports FORTRAN
43 Run-time Utilities
44 Option
45 _SC_2_LOCALEDEF _POSIX2_LOCALEDEF Supports creation
46 of locales by the
47 localedef utility
48 _SC_2_SW_DEV _POSIX2_SW_DEV Supports Software
49 Development Utility
50 Option
51 _SC_2_UPE _POSIX2_UPE Supports User
52 Portability
53 Utilities Option
54 _SC_2_VERSION _POSIX2_VERSION Integer value
55 indicates version
56 of ISO POSIX-2
57 standard (C language
58 binding)
59 _SC_AIO_LISTIO_MAX AIO_LISTIO_MAX Max number of I/O
60 operations in a
61 single list I/O call
62 supported
63 _SC_AIO_MAX AIO_MAX Max number of
64 outstanding
65 asynchronous I/O
66 operations supported
67 _SC_AIO_PRIO_DELTA_MAX AIO_PRIO_DELTA_MAX Max amount by which
68 process can decrease
69 its asynchronous
70 I/O priority level
71 from its own
72 scheduling priority
73 _SC_ARG_MAX ARG_MAX Max size of argv[]
74 plus envp[]
75 _SC_ASYNCHRONOUS_IO _POSIX_ASYNCHRONOUS_IO Supports
76 Asynchronous I/O
77 _SC_ATEXIT_MAX ATEXIT_MAX Max number of
78 functions that can
79 be registered with
80 atexit()
81 _SC_AVPHYS_PAGES Number of physical
82 memory pages not
83 currently in use by
84 system
85 _SC_BARRIERS _POSIX_BARRIERS Supports Barriers
86 option
87 _SC_BC_BASE_MAX BC_BASE_MAX Maximum obase values
88 allowed by bc
89 _SC_BC_DIM_MAX BC_DIM_MAX Max number of
90 elements permitted
91 in array by bc
92 _SC_BC_SCALE_MAX BC_SCALE_MAX Max scale value
93 allowed by bc
94 _SC_BC_STRING_MAX BC_STRING_MAX Max length of string
95 constant allowed by
96 bc
97 _SC_CHILD_MAX CHILD_MAX Max processes
98 allowed to a UID
99 _SC_CLK_TCK CLK_TCK Ticks per second
100 (clock_t)
101 _SC_CLOCK_SELECTION _POSIX_CLOCK_SELECTION Supports Clock
102 Selection option
103 _SC_COLL_WEIGHTS_MAX COLL_WEIGHTS_MAX Max number of
104 weights that can be
105 assigned to entry of
106 the LC_COLLATE order
107 keyword in locale
108 definition file
109 _SC_CPUID_MAX Max possible
110 processor ID
111 _SC_DELAYTIMER_MAX DELAYTIMER_MAX Max number of timer
112 expiration overruns
113 _SC_EXPR_NEST_MAX EXPR_NEST_MAX Max number of
114 parentheses by expr
115 _SC_FSYNC _POSIX_FSYNC Supports File
116 Synchronization
117 _SC_GETGR_R_SIZE_MAX Max size of group
118 entry buffer
119 _SC_GETPW_R_SIZE_MAX Max size of password
120 entry buffer
121 _SC_HOST_NAME_MAX _POSIX_HOST_NAME_MAX Maximum length of a
122 host name (excluding
123 terminating null)
124 _SC_IOV_MAX IOV_MAX Max number of iovec
125 structures available
126 to one process for
127 use with readv()
128 and writev()
129 _SC_JOB_CONTROL _POSIX_JOB_CONTROL Job control
130 supported?
131 _SC_LINE_MAX LINE_MAX Max length of input
132 line
133 _SC_LOGIN_NAME_MAX LOGNAME_MAX + 1 Max length of login
134 name
135 _SC_LOGNAME_MAX LOGNAME_MAX
136 _SC_MAPPED_FILES _POSIX_MAPPED_FILES Supports Memory
137 Mapped Files
138 _SC_MAXPID Max pid value
139 _SC_MEMLOCK _POSIX_MEMLOCK Supports Process
140 Memory Locking
141 _SC_MEMLOCK_RANGE _POSIX_MEMLOCK_RANGE Supports Range
142 Memory Locking
143 _SC_MEMORY_PROTECTION _POSIX_MEMORY_PROTECTION Supports Memory
144 Protection
145 _SC_MESSAGE_PASSING _POSIX_MESSAGE_PASSING Supports Message
146 Passing
147 _SC_MONOTONIC_CLOCK _POSIX_MONOTONIC_CLOCK Supports Monotonic
148 Clock option
149 _SC_MQ_OPEN_MAX MQ_OPEN_MAX Max number of open
150 message queues a
151 process can hold
152 _SC_MQ_PRIO_MAX MQ_PRIO_MAX Max number of
153 message priorities
154 supported
155 _SC_NGROUPS_MAX NGROUPS_MAX Max simultaneous
156 groups to which
157 one can belong
158 _SC_NPROCESSORS_CONF Number of processors
159 configured
160 _SC_NPROCESSORS_MAX Max number of
161 processors supported
162 by platform
163 _SC_NPROCESSORS_ONLN Number of processors
164 online
165 _SC_OPEN_MAX OPEN_MAX Max open files per
166 process
167 _SC_PAGESIZE PAGESIZE System memory page
168 size
169 _SC_PAGE_SIZE PAGESIZE Same as _SC_PAGESIZE
170 _SC_PASS_MAX PASS_MAX Max number of
171 significant bytes
172 in a password
173 _SC_PHYS_PAGES Total number of
174 pages of physical
175 memory in system
176 _SC_PRIORITIZED_IO _POSIX_PRIORITIZED_IO Supports Prioritized
177 I/O
178 _SC_PRIORITY_SCHEDULING _POSIX_PRIORITY_SCHEDULING Supports Process
179 Scheduling
180 _SC_RAW_SOCKETS _POSIX_RAW_SOCKETS Supports Raw Sockets
181 option
182 _SC_RE_DUP_MAX RE_DUP_MAX Max number of
183 repeated occurrences
184 of a regular
185 expression permitted
186 when using interval
187 notation \{m,n\}
188 _SC_READER_WRITER_LOCKS _POSIX_READER_WRITER_LOCKS Supports IPV6 option
189 _SC_REALTIME_SIGNALS _POSIX_REALTIME_SIGNALS Supports Realtime
190 Signals
191 _SC_REGEXP _POSIX_REGEXP Supports Regular
192 Expression Handling
193 option
194 _SC_RTSIG_MAX RTSIG_MAX Max number of
195 realtime signals
196 reserved for
197 application use
198 _SC_SAVED_IDS _POSIX_SAVED_IDS Saved IDs
199 (seteuid())
200 supported?
201 _SC_SEM_NSEMS_MAX SEM_NSEMS_MAX Max number of POSIX
202 semaphores a process
203 can have
204 _SC_SEM_VALUE_MAX SEM_VALUE_MAX Max value a POSIX
205 semaphore can have
206 _SC_SEMAPHORES _POSIX_SEMAPHORES Supports Semaphores
207 _SC_SHARED_MEMORY_ _POSIX_SHARED_MEMORY_ Supports Shared
208 OBJECTS OBJECTS Memory Objects
209 _SC_SHELL _POSIX_SHELL Supports POSIX shell
210 _SC_SIGQUEUE_MAX SIGQUEUE_MAX Max number of queued
211 signals that a
212 process can send and
213 have pending at
214 receiver(s) at a
215 time
216 _SC_SPAWN _POSIX_SPAWN Supports Spawn option
217 _SC_SPIN_LOCKS _POSIX_SPIN_LOCKS Supports Spin Locks
218 option
219 _SC_STACK_PROT Default stack
220 protection
221 _SC_STREAM_MAX STREAM_MAX Number of streams
222 one process can
223 have open at a time
224 _SC_SYMLOOP_MAX _POSIX_SYMLOOP_MAX Max number of symbolic
225 links that can be
226 reliably traversed in
227 the resolution of a
228 pathname in the absence
229 of a loop
230 _SC_SYNCHRONIZED_IO _POSIX_SYNCHRONIZED_IO Supports
231 Synchronized I/O
232 _SC_THREAD_ATTR_ _POSIX_THREAD_ATTR_ Supports Thread
233 STACKADDR STACKADDR Stack Address
234 Attribute option
235 _SC_THREAD_ATTR_ _POSIX_THREAD_ATTR_ Supports Thread
236 STACKSIZE STACKSIZE Stack Size
237 Attribute option
238 _SC_THREAD_DESTRUCTOR_ PTHREAD_DESTRUCTOR_ Number attempts made
239 ITERATIONS ITERATIONS to destroy thread-
240 specific data on
241 thread exit
242 _SC_THREAD_KEYS_MAX PTHREAD_KEYS_MAX Max number of data
243 keys per process
244 _SC_THREAD_PRIO_ _POSIX_THREAD_PRIO_ Supports Priority
245 INHERIT INHERIT Inheritance option
246 _SC_THREAD_PRIO_ _POSIX_THREAD_PRIO_ Supports Priority
247 PROTECT PROTECT Protection option
248 _SC_THREAD_PRIORITY_ _POSIX_THREAD_PRIORITY_ Supports Thread
249 SCHEDULING SCHEDULING Execution
250 Scheduling option
251 _SC_THREAD_PROCESS_ _POSIX_THREAD_PROCESS_ Supports
252 SHARED SHARED Process-Shared
253 Synchronization
254 option
255 _SC_THREAD_SAFE_ _POSIX_THREAD_SAFE_ Supports Thread-Safe
256 FUNCTIONS FUNCTIONS Functions option
257 _SC_THREAD_STACK_MIN PTHREAD_STACK_MIN Min byte size of
258 thread stack storage
259 _SC_THREAD_THREADS_MAX PTHREAD_THREADS_MAX Max number of
260 threads per process
261 _SC_THREADS _POSIX_THREADS Supports Threads
262 option
263 _SC_TIMEOUTS _POSIX_TIMEOUTS Supports Timeouts
264 option
265 _SC_TIMER_MAX TIMER_MAX Max number of timer
266 per process
267 supported
268 _SC_TIMERS _POSIX_TIMERS Supports Timers
269 _SC_TTY_NAME_MAX TTYNAME_MAX Max length of tty
270 device name
271 _SC_TZNAME_MAX TZNAME_MAX Max number of bytes
272 supported for name
273 of a time zone
274 _SC_V6_ILP32_OFF32 _POSIX_V6_ILP32_OFF32 Supports X/Open
275 ILP32 w/32-bit
276 offset build
277 environment
278 _SC_V6_ILP32_OFFBIG _POSIX_V6_ILP32_OFFBIG Supports X/Open
279 ILP32 w/64-bit
280 offset build
281 environment
282 _SC_V6_LP64_OFF64 _POSIX_V6_LP64_OFF64 Supports X/Open
283 LP64 w/64-bit
284 offset build
285 environment
286 _SC_V6_LPBIG_OFFBIG _POSIX_V6_LPBIG_OFFBIG Same as
287 _SC_V6_LP64_OFF64
288 _SC_VERSION _POSIX_VERSION POSIX.1 version
289 supported
290 _SC_XBS5_ILP32_OFF32 _XBS_ILP32_OFF32 Indicates support
291 for X/Open ILP32
292 w/32-bit offset
293 build environment
294 _SC_XBS5_ILP32_OFFBIG _XBS5_ILP32_OFFBIG Indicates support
295 for X/Open ILP32
296 w/64-bit offset
297 build environment
298 _SC_XBS5_LP64_OFF64 _XBS5_LP64_OFF64 Indicates support of
299 X/Open LP64,
300 64-bit offset
301 build environment
302 _SC_XBS5_LPBIG_OFFBIG _XBS5_LP64_OFF64 Same as
303 _SC_XBS5_LP64_OFF64
304 _SC_XOPEN_CRYPT _XOPEN_CRYPT Supports X/Open
305 Encryption Feature
306 Group
307 _SC_XOPEN_ENH_I18N _XOPEN_ENH_I18N Supports X/Open
308 Enhanced
309 Internationalization
310 Feature Group
311 _SC_XOPEN_LEGACY _XOPEN_LEGACY Supports X/Open
312 Legacy Feature Group
313 _SC_XOPEN_REALTIME _XOPEN_REALTIME Supports X/Open
314 POSIX Realtime
315 Feature Group
316 _SC_XOPEN_REALTIME_ _XOPEN_REALTIME_THREADS Supports X/Open
317 THREADS POSIX Reatime
318 Threads Feature
319 Group
320 _SC_XOPEN_SHM _XOPEN_SHM Supports X/Open
321 Shared Memory
322 Feature Group
323 _SC_XOPEN_STREAMS _POSIX_XOPEN_STREAMS Supports XSI Streams
324 option group
325 _SC_XOPEN_UNIX _XOPEN_UNIX Supports X/Open CAE
326 Specification,
327 August 1994, System
328 Interfaces and
329 Headers, Issue 4,
330 Version 2
331 _SC_XOPEN_VERSION _XOPEN_VERSION Integer value
332 indicates version of
333 X/Open Portability
334 Guide to which
335 implementation
336 conforms
337 _SC_XOPEN_XCU_VERSION _XOPEN_XCU_VERSION Integer value
338 indicates version of
339 XCU specification to
340 which implementation
341 conforms
342 The following options are not supported and return −1:
347 _SC_2_PBS _POSIX2_PBS
352 _SC_2_PBS_ACCOUNTING _POSIX2_PBS_ACCOUNTING
353 _SC_2_PBS_CHECKPOINT _POSIX2_PBS_CHECKPOINT
354 _SC_2_PBS_LOCATE _POSIX2_PBS_LOCATE
355 _SC_2_PBS_MESSAGE _POSIX2_PBS_MESSAGE
356 _SC_2_PBS_TRACK _POSIX2_PBS_TRACK
357 _SC_ADVISORY_INFO _POSIX_ADVISORY_INFO
358 _SC_CPUTIME _POSIX_CPUTIME
359 _SC_SPORADIC_SERVER _POSIX_SPORADIC_SERVER
360 _SC_SS_REPL_MAX _POSIX_SS_REPL_MAX
361 _SC_THREAD_CPUTIME _POSIX_THREAD_CPUTIME
362 _SC_THREAD_SPORADIC_SERVER _POSIX_THREAD_SPORADIC_SERVER
363 _SC_TRACE _POSIX_TRACE
364 _SC_TRACE_EVENT_FILTER _POSIX_TRACE_EVENT_FILTER
365 _SC_TRACE_EVENT_NAME_MAX _POSIX_TRACE_EVENT_NAME_MAX
366 _SC_TRACE_INHERIT _POSIX_TRACE_INHERIT
367 _SC_TRACE_LOG _POSIX_TRACE_LOG
368 _SC_TRACE_NAME_MAX _POSIX_TRACE_NAME_MAX
369 _SC_TRACE_SYS_MAX _POSIX_TRACE_SYS_MAX
370 _SC_TRACE_USER_EVENT_MAX _POSIX_TRACE_USER_EVENT_MAX
371 _SC_TYPED_MEMORY_OBJECTS _POSIX_TYPED_MEMORY_OBJECTS
372
375 Upon successful completion, sysconf() returns the current variable
376 value on the system. The value returned will not be more restrictive
377 than the corresponding value described to the application when it was
378 compiled with the implementation's <limits.h>, <unistd.h> or <time.h>.
379 With only a few obvious exceptions such as _SC_AVPHYS_PAGES and
380 _SC_NPROCESSORS_ONLN, the value will not change during the lifetime of
381 the calling process.
382 If name is an invalid value, sysconf() returns −1 and sets errno to
385 indicate the error. If the variable corresponding to name is associated
386 with functionality that is not supported by the system, sysconf()
387 returns −1 without changing the value of errno.
388 Calling sysconf() with the following returns −1 without setting errno,
391 because no maximum limit can be determined. The system supports at
392 least the minimum values and can support higher values depending upon
393 system resources.
394 Variable Minimum supported value
396 _SC_AIO_MAX _POSIX_AIO_MAX
397 _SC_ATEXIT_MAX 32
398 _SC_MQ_OPEN_MAX 32
399 _SC_THREAD_THREADS_MAX _POSIX_THREAD_THREADS_MAX
400 _SC_THREAD_KEYS_MAX _POSIX_THREAD_KEYS_MAX
401 _SC_THREAD_DESTRUCTOR_ITERATIONS _POSIX_THREAD_DESTRUCTOR_ITERATIONS
402 The following SPARC and x86 platform variables return EINVAL:
406 _SC_COHER_BLKSZ _SC_DCACHE_ASSOC
408 _SC_DCACHE_BLKSZ _SC_DCACHE_LINESZ
409 _SC_DCACHE_SZ _SC_DCACHE_TBLKSZ
410 _SC_ICACHE_ASSOC _SC_ICACHE_BLKSZ
411 _SC_ICACHE_LINESZ _SC_ICACHE_SZ
412 _SC_SPLIT_CACHE
413
416 The sysconf() function will fail if:
417 EINVAL The value of the name argument is invalid.
419
422 See attributes(5) for descriptions of the following attributes:
423 ┌─────────────────────────────┬─────────────────────────────┐
428 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
429 ├─────────────────────────────┼─────────────────────────────┤
430 │Architecture │SPARC and x86 │
431 ├─────────────────────────────┼─────────────────────────────┤
432 │Interface Stability │Committed │
433 ├─────────────────────────────┼─────────────────────────────┤
434 │MT-Level │MT-Safe, Async-Signal-Safe │
435 ├─────────────────────────────┼─────────────────────────────┤
436 │Standard │See standards(5). │
437 └─────────────────────────────┴─────────────────────────────┘
438
440 pooladm(1M), zoneadm(1M), fpathconf(2), seteuid(2), setrlimit(2), conf‐
441 str(3C), attributes(5), standards(5)
442
444 A call to setrlimit() can cause the value of OPEN_MAX to change.
445 Multiplying sysconf(_SC_PHYS_PAGES) or sysconf(_SC_AVPHYS_PAGES) by
448 sysconf(_SC_PAGESIZE) to determine memory amount in bytes can exceed
449 the maximum values representable in a 32-bit signed or unsigned inte‐
450 ger.
451 The value of CLK_TCK can be variable and it should not be assumed that
454 CLK_TCK is a compile-time constant.
455 If the caller is in a non-global zone and the pools facility is active,
458 sysconf(_SC_NPROCESSORS_CONF) and sysconf(_SC_NPROCESSORS_ONLN) return
459 the number of processors in the processor set of the pool to which the
460 zone is bound.
461SunOS 5.11 26 Mar 2008 sysconf(3C)