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32 .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95
33 .\" $FreeBSD: src/lib/libc/gen/sysctl.3,v 1.33.2.13 2002/04/07 04:57:14 dd Exp $
34 .\" $DragonFly: src/lib/libc/gen/sysctl.3,v 1.9 2007/10/26 08:22:00 swildner Exp $
35 .\"
36 .Dd January 23, 2001
37 .Dt SYSCTL 3
38 .Os
39 .Sh NAME
40 .Nm sysctl ,
41 .Nm sysctlbyname ,
42 .Nm sysctlnametomib
43 .Nd get or set system information
44 .Sh LIBRARY
45 .Lb libc
46 .Sh SYNOPSIS
47 .In sys/types.h
48 .In sys/sysctl.h
49 .Ft int
50 .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
51 .Ft int
52 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
53 .Ft int
54 .Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep"
55 .Sh DESCRIPTION
56 The
57 .Fn sysctl
58 function retrieves system information and allows processes with
59 appropriate privileges to set system information.
60 The information available from
61 .Fn sysctl
62 consists of integers, strings, and tables.
63 Information may be retrieved and set from the command interface
64 using the
65 .Xr sysctl 8
66 utility.
67 .Pp
68 Unless explicitly noted below,
69 .Fn sysctl
70 returns a consistent snapshot of the data requested.
71 Consistency is obtained by locking the destination
72 buffer into memory so that the data may be copied out without blocking.
73 Calls to
74 .Fn sysctl
75 are serialized to avoid deadlock.
76 .Pp
77 The state is described using a ``Management Information Base'' (MIB)
78 style name, listed in
79 .Fa name ,
80 which is a
81 .Fa namelen
82 length array of integers.
83 .Pp
84 The
85 .Fn sysctlbyname
86 function accepts an ASCII representation of the name and internally
87 looks up the integer name vector. Apart from that, it behaves the same
88 as the standard
89 .Fn sysctl
90 function.
91 .Pp
92 The information is copied into the buffer specified by
93 .Fa oldp .
94 The size of the buffer is given by the location specified by
95 .Fa oldlenp
96 before the call,
97 and that location gives the amount of data copied after a successful call
98 and after a call that returns with the error code
99 .Er ENOMEM .
100 If the amount of data available is greater
101 than the size of the buffer supplied,
102 the call supplies as much data as fits in the buffer provided
103 and returns with the error code
104 .Er ENOMEM .
105 If the old value is not desired,
106 .Fa oldp
107 and
108 .Fa oldlenp
109 should be set to NULL.
110 .Pp
111 The size of the available data can be determined by calling
112 .Fn sysctl
113 with a NULL parameter for
114 .Fa oldp .
115 The size of the available data will be returned in the location pointed to by
116 .Fa oldlenp .
117 For some operations, the amount of space may change often.
118 For these operations,
119 the system attempts to round up so that the returned size is
120 large enough for a call to return the data shortly thereafter.
121 .Pp
122 To set a new value,
123 .Fa newp
124 is set to point to a buffer of length
125 .Fa newlen
126 from which the requested value is to be taken.
127 If a new value is not to be set,
128 .Fa newp
129 should be set to NULL and
130 .Fa newlen
131 set to 0.
132 .Pp
133 The
134 .Fn sysctlnametomib
135 function accepts an ASCII representation of the name,
136 looks up the integer name vector,
137 and returns the numeric representation in the mib array pointed to by
138 .Fa mibp .
139 The number of elements in the mib array is given by the location specified by
140 .Fa sizep
141 before the call,
142 and that location gives the number of entries copied after a successful call.
143 The resulting
144 .Fa mib
145 and
146 .Fa size
147 may be used in subsequent
148 .Fn sysctl
149 calls to get the data associated with the requested ASCII name.
150 This interface is intended for use by applications that want to
151 repeatedly request the same variable (the
152 .Fn sysctl
153 function runs in about a third the time as the same request made via the
154 .Fn sysctlbyname
155 function).
156 The
157 .Fn sysctlnametomib
158 function is also useful for fetching mib prefixes and then adding
159 a final component.
160 For example, to fetch process information
161 for processes with pid's less than 100:
162 .Pp
163 .Bd -literal -offset indent -compact
164 int i, mib[4];
165 size_t len;
166 struct kinfo_proc kp;
168 /* Fill out the first three components of the mib */
169 len = 4;
170 sysctlnametomib("kern.proc.pid", mib, &len);
172 /* Fetch and print entries for pid's < 100 */
173 for (i = 0; i < 100; i++) {
174 mib[3] = i;
175 len = sizeof(kp);
176 if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
177 perror("sysctl");
178 else if (len > 0)
179 printkproc(&kp);
180 }
181 .Ed
182 .Pp
183 The top level names are defined with a CTL_ prefix in
184 .In sys/sysctl.h ,
185 and are as follows.
186 The next and subsequent levels down are found in the include files
187 listed here, and described in separate sections below.
188 .Pp
189 .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
190 .It Sy "Name Next level names Description"
191 .It "CTL\_DEBUG sys/sysctl.h Debugging"
192 .It "CTL\_VFS sys/mount.h Filesystem"
193 .It "CTL\_HW sys/sysctl.h Generic CPU, I/O"
194 .It "CTL\_KERN sys/sysctl.h High kernel limits"
195 .It "CTL\_MACHDEP sys/sysctl.h Machine dependent"
196 .It "CTL\_NET sys/socket.h Networking"
197 .It "CTL\_USER sys/sysctl.h User-level"
198 .It "CTL\_VM vm/vm_param.h Virtual memory"
199 .El
200 .Pp
201 For example, the following retrieves the maximum number of processes allowed
202 in the system:
203 .Pp
204 .Bd -literal -offset indent -compact
205 int mib[2], maxproc;
206 size_t len;
208 mib[0] = CTL_KERN;
209 mib[1] = KERN_MAXPROC;
210 len = sizeof(maxproc);
211 sysctl(mib, 2, &maxproc, &len, NULL, 0);
212 .Ed
213 .Pp
214 To retrieve the standard search path for the system utilities:
215 .Pp
216 .Bd -literal -offset indent -compact
217 int mib[2];
218 size_t len;
219 char *p;
221 mib[0] = CTL_USER;
222 mib[1] = USER_CS_PATH;
223 sysctl(mib, 2, NULL, &len, NULL, 0);
224 p = malloc(len);
225 sysctl(mib, 2, p, &len, NULL, 0);
226 .Ed
227 .Ss CTL_DEBUG
228 The debugging variables vary from system to system.
229 A debugging variable may be added or deleted without need to recompile
230 .Fn sysctl
231 to know about it.
232 Each time it runs,
233 .Fn sysctl
234 gets the list of debugging variables from the kernel and
235 displays their current values.
236 The system defines twenty
237 .Ns ( Va struct ctldebug )
238 variables named
239 .Nm debug0
240 through
241 .Nm debug19 .
242 They are declared as separate variables so that they can be
243 individually initialized at the location of their associated variable.
244 The loader prevents multiple use of the same variable by issuing errors
245 if a variable is initialized in more than one place.
246 For example, to export the variable
247 .Nm dospecialcheck
248 as a debugging variable, the following declaration would be used:
249 .Bd -literal -offset indent -compact
250 int dospecialcheck = 1;
251 struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
252 .Ed
253 .Ss CTL_VFS
254 A distinguished second level name, VFS_GENERIC,
255 is used to get general information about all filesystems.
256 One of its third level identifiers is VFS_MAXTYPENUM
257 that gives the highest valid filesystem type number.
258 Its other third level identifier is VFS_CONF that
259 returns configuration information about the filesystem
260 type given as a fourth level identifier (see
261 .Xr getvfsbyname 3
262 as an example of its use).
263 The remaining second level identifiers are the
264 filesystem type number returned by a
265 .Xr statfs 2
266 call or from VFS_CONF.
267 The third level identifiers available for each filesystem
268 are given in the header file that defines the mount
269 argument structure for that filesystem.
270 .Ss CTL_HW
271 The string and integer information available for the CTL_HW level
272 is detailed below.
273 The changeable column shows whether a process with appropriate
274 privilege may change the value.
275 .Bl -column "Second level nameXXXXXX" integerXXX -offset indent
276 .It Sy "Second level name Type Changeable"
277 .It "HW\_MACHINE string no"
278 .It "HW\_MODEL string no"
279 .It "HW\_NCPU integer no"
280 .It "HW\_BYTEORDER integer no"
281 .It "HW\_PHYSMEM integer no"
282 .It "HW\_USERMEM integer no"
283 .It "HW\_PAGESIZE integer no"
284 .It "HW\_FLOATINGPOINT integer no"
285 .It "HW\_MACHINE\_ARCH string no"
286 .\".It "HW\_DISKNAMES integer no"
287 .\".It "HW\_DISKSTATS integer no"
288 .It "HW_SENSORS node not applicable"
289 .El
290 .Pp
291 .Bl -tag -width 6n
292 .It Li HW_MACHINE
293 The machine class.
294 .It Li HW_MODEL
295 The machine model
296 .It Li HW_NCPU
297 The number of cpus.
298 .It Li HW_BYTEORDER
299 The byteorder (4,321, or 1,234).
300 .It Li HW_PHYSMEM
301 The bytes of physical memory.
302 .It Li HW_USERMEM
303 The bytes of non-kernel memory.
304 .It Li HW_PAGESIZE
305 The software page size.
306 .It Li HW_FLOATINGPOINT
307 Nonzero if the floating point support is in hardware.
308 .It Li HW_MACHINE_ARCH
309 The machine dependent architecture type.
310 .\".It Fa HW_DISKNAMES
311 .\".It Fa HW_DISKSTATS
312 .It Li HW_SENSORS
313 Third level comprises an array of
314 .Vt "struct sensordev"
315 structures containing information about devices
316 that may attach hardware monitoring sensors.
317 .Pp
318 Third, fourth and fifth levels together comprise an array of
319 .Vt "struct sensor"
320 structures containing snapshot readings of hardware monitoring sensors.
321 In such usage, third level indicates the numerical representation
322 of the sensor device name to which the sensor is attached
323 (device's
324 .Va xname
325 and number shall be matched with the help of
326 .Vt "struct sensordev"
327 structure above),
328 fourth level indicates sensor type and
329 fifth level is an ordinal sensor number (unique to
330 the specified sensor type on the specified sensor device).
331 .Pp
332 The
333 .Vt sensordev
334 and
335 .Vt sensor
336 structures
337 and
338 .Vt sensor_type
339 enumeration
340 are defined in
341 .In sys/sensors.h .
342 .El
343 .Ss CTL_KERN
344 The string and integer information available for the CTL_KERN level
345 is detailed below.
346 The changeable column shows whether a process with appropriate
347 privilege may change the value.
348 The types of data currently available are process information,
349 system vnodes, the open file entries, routing table entries,
350 virtual memory statistics, load average history, and clock rate
351 information.
352 .Bl -column "KERNXMAXPOSIXLOCKSPERUIDXXX" "struct clockrateXXX" -offset indent
353 .It Sy "Second level name Type Changeable"
354 .It "KERN\_ARGMAX integer no"
355 .It "KERN\_BOOTFILE string yes"
356 .It "KERN\_BOOTTIME struct timeval no"
357 .It "KERN\_CLOCKRATE struct clockinfo no"
358 .It "KERN\_FILE struct file no"
359 .It "KERN\_HOSTID integer yes"
360 .It "KERN\_HOSTNAME string yes"
361 .It "KERN\_JOB\_CONTROL integer no"
362 .It "KERN\_MAXFILES integer yes"
363 .It "KERN\_MAXFILESPERPROC integer yes"
364 .It "KERN\_MAXPOSIXLOCKSPERUID integer yes"
365 .It "KERN\_MAXPROC integer no"
366 .It "KERN\_MAXPROCPERUID integer yes"
367 .It "KERN\_MAXVNODES integer yes"
368 .It "KERN\_NGROUPS integer no"
369 .It "KERN\_NISDOMAINNAME string yes"
370 .It "KERN\_OSRELDATE integer no"
371 .It "KERN\_OSRELEASE string no"
372 .It "KERN\_OSREV integer no"
373 .It "KERN\_OSTYPE string no"
374 .It "KERN\_POSIX1 integer no"
375 .It "KERN\_PROC struct proc no"
376 .It "KERN\_PROF node not applicable"
377 .It "KERN\_QUANTUM integer yes"
378 .It "KERN\_SAVED\_IDS integer no"
379 .It "KERN\_SECURELVL integer raise only"
380 .It "KERN\_UPDATEINTERVAL integer no"
381 .It "KERN\_VERSION string no"
382 .It "KERN\_VNODE struct vnode no"
383 .El
384 .Pp
385 .Bl -tag -width 6n
386 .It Li KERN_ARGMAX
387 The maximum bytes of argument to
388 .Xr execve 2 .
389 .It Li KERN_BOOTFILE
390 The full pathname of the file from which the kernel was loaded.
391 .It Li KERN_BOOTTIME
392 A
393 .Va struct timeval
394 structure is returned.
395 This structure contains the time that the system was booted.
396 .It Li KERN_CLOCKRATE
397 A
398 .Va struct clockinfo
399 structure is returned.
400 This structure contains the clock, statistics clock and profiling clock
401 frequencies, the number of micro-seconds per hz tick and the skew rate.
402 .It Li KERN_FILE
403 Return the entire file table.
404 The returned data consists of a single
405 .Va struct filehead
406 followed by an array of
407 .Va struct file ,
408 whose size depends on the current number of such objects in the system.
409 .It Li KERN_HOSTID
410 Get or set the host id.
411 .It Li KERN_HOSTNAME
412 Get or set the hostname.
413 .It Li KERN_JOB_CONTROL
414 Return 1 if job control is available on this system, otherwise 0.
415 .It Li KERN_MAXFILES
416 The maximum number of files that may be open in the system.
417 .It Li KERN_MAXFILESPERPROC
418 The maximum number of files that may be open for a single process.
419 This limit only applies to processes with an effective uid of nonzero
420 at the time of the open request.
421 Files that have already been opened are not affected if the limit
422 or the effective uid is changed.
423 .It Li KERN_MAXPROC
424 The maximum number of concurrent processes the system will allow.
425 .It Li KERN_MAXPROCPERUID
426 The maximum number of concurrent processes the system will allow
427 for a single effective uid.
428 This limit only applies to processes with an effective uid of nonzero
429 at the time of a fork request.
430 Processes that have already been started are not affected if the limit
431 is changed.
432 .It Li KERN_MAXVNODES
433 The maximum number of vnodes available on the system.
434 .It Li KERN_NGROUPS
435 The maximum number of supplemental groups.
436 .It Li KERN_NISDOMAINNAME
437 The name of the current YP/NIS domain.
438 .It Li KERN_OSRELDATE
439 The system release date in YYYYMM format
440 (January 1996 is encoded as 199601).
441 .It Li KERN_OSRELEASE
442 The system release string.
443 .It Li KERN_OSREV
444 The system revision string.
445 .It Li KERN_OSTYPE
446 The system type string.
447 .It Li KERN_POSIX1
448 The version of
449 .St -p1003.1
450 with which the system
451 attempts to comply.
452 .It Li KERN_PROC
453 Return the entire process table, or a subset of it.
454 An array of
455 .Va struct kinfo_proc
456 structures is returned,
457 whose size depends on the current number of such objects in the system.
458 The third and fourth level names are as follows:
459 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
460 .It "Third level name Fourth level is:"
461 .It "KERN\_PROC\_ALL None"
462 .It "KERN\_PROC\_PID A process ID"
463 .It "KERN\_PROC\_PGRP A process group"
464 .It "KERN\_PROC\_TTY A tty device"
465 .It "KERN\_PROC\_UID A user ID"
466 .It "KERN\_PROC\_RUID A real user ID"
467 .El
468 .Pp
469 Adding the flag
470 .Li KERN_PROC_FLAG_LWP
471 to the third level name signals that information about all
472 light weight processes of the selected processes should be returned.
473 .It Li KERN_PROF
474 Return profiling information about the kernel.
475 If the kernel is not compiled for profiling,
476 attempts to retrieve any of the KERN_PROF values will
477 fail with
478 .Er ENOENT .
479 The third level names for the string and integer profiling information
480 is detailed below.
481 The changeable column shows whether a process with appropriate
482 privilege may change the value.
483 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
484 .It Sy "Third level name Type Changeable"
485 .It "GPROF\_STATE integer yes"
486 .It "GPROF\_COUNT u_short[\|] yes"
487 .It "GPROF\_FROMS u_short[\|] yes"
488 .It "GPROF\_TOS struct tostruct yes"
489 .It "GPROF\_GMONPARAM struct gmonparam no"
490 .El
491 .Pp
492 The variables are as follows:
493 .Bl -tag -width 6n
494 .It Li GPROF_STATE
495 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
496 is running or stopped.
497 .It Li GPROF_COUNT
498 Array of statistical program counter counts.
499 .It Li GPROF_FROMS
500 Array indexed by program counter of call-from points.
501 .It Li GPROF_TOS
502 Array of
503 .Va struct tostruct
504 describing destination of calls and their counts.
505 .It Li GPROF_GMONPARAM
506 Structure giving the sizes of the above arrays.
507 .El
508 .It Li KERN_QUANTUM
509 The maximum period of time, in microseconds, for which a process is allowed
510 to run without being preempted if other processes are in the run queue.
511 .It Li KERN_SAVED_IDS
512 Returns 1 if saved set-group and saved set-user ID is available.
513 .It Li KERN_SECURELVL
514 The system security level.
515 This level may be raised by processes with appropriate privilege.
516 It may not be lowered.
517 .It Li KERN_VERSION
518 The system version string.
519 .It Li KERN_VNODE
520 Return the entire vnode table.
521 Note, the vnode table is not necessarily a consistent snapshot of
522 the system.
523 The returned data consists of an array whose size depends on the
524 current number of such objects in the system.
525 Each element of the array contains the kernel address of a vnode
526 .Va struct vnode *
527 followed by the vnode itself
528 .Va struct vnode .
529 .El
530 .Ss CTL_MACHDEP
531 The set of variables defined is architecture dependent.
532 The following variables are defined for the i386 architecture.
533 .Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent
534 .It Sy "Second level name Type Changeable"
535 .It Li "CPU_CONSDEV dev_t no"
536 .It Li "CPU_ADJKERNTZ int yes"
537 .It Li "CPU_DISRTCSET int yes"
538 .It Li "CPU_BOOTINFO struct bootinfo no"
539 .It Li "CPU_WALLCLOCK int yes"
540 .El
541 .Ss CTL_NET
542 The string and integer information available for the CTL_NET level
543 is detailed below.
544 The changeable column shows whether a process with appropriate
545 privilege may change the value.
546 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
547 .It Sy "Second level name Type Changeable"
548 .It "PF\_ROUTE routing messages no"
549 .It "PF\_INET IPv4 values yes"
550 .It "PF\_INET6 IPv6 values yes"
551 .El
552 .Pp
553 .Bl -tag -width 6n
554 .It Li PF_ROUTE
555 Return the entire routing table or a subset of it.
556 The data is returned as a sequence of routing messages (see
557 .Xr route 4
558 for the header file, format and meaning).
559 The length of each message is contained in the message header.
560 .Pp
561 The third level name is a protocol number, which is currently always 0.
562 The fourth level name is an address family, which may be set to 0 to
563 select all address families.
564 The fifth and sixth level names are as follows:
565 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
566 .It Sy "Fifth level name Sixth level is:"
567 .It "NET\_RT\_FLAGS rtflags"
568 .It "NET\_RT\_DUMP None"
569 .It "NET\_RT\_IFLIST None"
570 .El
571 .It Li PF_INET
572 Get or set various global information about the IPv4
573 (Internet Protocol version 4).
574 The third level name is the protocol.
575 The fourth level name is the variable name.
576 The currently defined protocols and names are:
577 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
578 .It Sy "Protocol Variable Type Changeable"
579 .It "icmp bmcastecho integer yes"
580 .It "icmp maskrepl integer yes"
581 .It "ip forwarding integer yes"
582 .It "ip redirect integer yes"
583 .It "ip ttl integer yes"
584 .It "udp checksum integer yes"
585 .El
586 .Pp
587 The variables are as follows:
588 .Bl -tag -width 6n
589 .It Li icmp.bmcastecho
590 Returns 1 if an ICMP echo request to a broadcast or multicast address is
591 to be answered.
592 .It Li icmp.maskrepl
593 Returns 1 if ICMP network mask requests are to be answered.
594 .It Li ip.forwarding
595 Returns 1 when IP forwarding is enabled for the host,
596 meaning that the host is acting as a router.
597 .It Li ip.redirect
598 Returns 1 when ICMP redirects may be sent by the host.
599 This option is ignored unless the host is routing IP packets,
600 and should normally be enabled on all systems.
601 .It Li ip.ttl
602 The maximum time-to-live (hop count) value for an IP packet sourced by
603 the system.
604 This value applies to normal transport protocols, not to ICMP.
605 .It Li udp.checksum
606 Returns 1 when UDP checksums are being computed and checked.
607 Disabling UDP checksums is strongly discouraged.
608 .Pp
609 For variables net.inet.*.ipsec, please refer to
610 .Xr ipsec 4 .
611 .El
612 .It Li PF_INET6
613 Get or set various global information about the IPv6
614 (Internet Protocol version 6).
615 The third level name is the protocol.
616 The fourth level name is the variable name.
617 .Pp
618 For variables net.inet6.* please refer to
619 .Xr inet6 4 .
620 For variables net.inet6.*.ipsec6, please refer to
621 .Xr ipsec 4 .
622 .El
623 .Ss CTL_USER
624 The string and integer information available for the CTL_USER level
625 is detailed below.
626 The changeable column shows whether a process with appropriate
627 privilege may change the value.
628 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
629 .It Sy "Second level name Type Changeable"
630 .It "USER\_BC\_BASE\_MAX integer no"
631 .It "USER\_BC\_DIM\_MAX integer no"
632 .It "USER\_BC\_SCALE\_MAX integer no"
633 .It "USER\_BC\_STRING\_MAX integer no"
634 .It "USER\_COLL\_WEIGHTS\_MAX integer no"
635 .It "USER\_CS\_PATH string no"
636 .It "USER\_EXPR\_NEST\_MAX integer no"
637 .It "USER\_LINE\_MAX integer no"
638 .It "USER\_POSIX2\_CHAR\_TERM integer no"
639 .It "USER\_POSIX2\_C\_BIND integer no"
640 .It "USER\_POSIX2\_C\_DEV integer no"
641 .It "USER\_POSIX2\_FORT\_DEV integer no"
642 .It "USER\_POSIX2\_FORT\_RUN integer no"
643 .It "USER\_POSIX2\_LOCALEDEF integer no"
644 .It "USER\_POSIX2\_SW\_DEV integer no"
645 .It "USER\_POSIX2\_UPE integer no"
646 .It "USER\_POSIX2\_VERSION integer no"
647 .It "USER\_RE\_DUP\_MAX integer no"
648 .It "USER\_STREAM\_MAX integer no"
649 .It "USER\_TZNAME\_MAX integer no"
650 .El
651 .Bl -tag -width 6n
652 .Pp
653 .It Li USER_BC_BASE_MAX
654 The maximum ibase/obase values in the
655 .Xr bc 1
656 utility.
657 .It Li USER_BC_DIM_MAX
658 The maximum array size in the
659 .Xr bc 1
660 utility.
661 .It Li USER_BC_SCALE_MAX
662 The maximum scale value in the
663 .Xr bc 1
664 utility.
665 .It Li USER_BC_STRING_MAX
666 The maximum string length in the
667 .Xr bc 1
668 utility.
669 .It Li USER_COLL_WEIGHTS_MAX
670 The maximum number of weights that can be assigned to any entry of
671 the LC_COLLATE order keyword in the locale definition file.
672 .It Li USER_CS_PATH
673 Return a value for the
674 .Ev PATH
675 environment variable that finds all the standard utilities.
676 .It Li USER_EXPR_NEST_MAX
677 The maximum number of expressions that can be nested within
678 parenthesis by the
679 .Xr expr 1
680 utility.
681 .It Li USER_LINE_MAX
682 The maximum length in bytes of a text-processing utility's input
683 line.
684 .It Li USER_POSIX2_CHAR_TERM
685 Return 1 if the system supports at least one terminal type capable of
686 all operations described in
687 .St -p1003.2 ,
688 otherwise 0.
689 .It Li USER_POSIX2_C_BIND
690 Return 1 if the system's C-language development facilities support the
691 C-Language Bindings Option, otherwise 0.
692 .It Li USER_POSIX2_C_DEV
693 Return 1 if the system supports the C-Language Development Utilities Option,
694 otherwise 0.
695 .It Li USER_POSIX2_FORT_DEV
696 Return 1 if the system supports the FORTRAN Development Utilities Option,
697 otherwise 0.
698 .It Li USER_POSIX2_FORT_RUN
699 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
700 otherwise 0.
701 .It Li USER_POSIX2_LOCALEDEF
702 Return 1 if the system supports the creation of locales, otherwise 0.
703 .It Li USER_POSIX2_SW_DEV
704 Return 1 if the system supports the Software Development Utilities Option,
705 otherwise 0.
706 .It Li USER_POSIX2_UPE
707 Return 1 if the system supports the User Portability Utilities Option,
708 otherwise 0.
709 .It Li USER_POSIX2_VERSION
710 The version of
711 .St -p1003.2
712 with which the system attempts to comply.
713 .It Li USER_RE_DUP_MAX
714 The maximum number of repeated occurrences of a regular expression
715 permitted when using interval notation.
716 .It Li USER_STREAM_MAX
717 The minimum maximum number of streams that a process may have open
718 at any one time.
719 .It Li USER_TZNAME_MAX
720 The minimum maximum number of types supported for the name of a
721 timezone.
722 .El
723 .Ss CTL_VM
724 The string and integer information available for the CTL_VM level
725 is detailed below.
726 The changeable column shows whether a process with appropriate
727 privilege may change the value.
728 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
729 .It Sy "Second level name Type Changeable"
730 .It "VM\_LOADAVG struct loadavg no"
731 .It "VM\_METER struct vmtotal no"
732 .It "VM\_PAGEOUT\_ALGORITHM integer yes"
733 .It "VM\_SWAPPING\_ENABLED integer maybe"
734 .It "VM\_V\_CACHE\_MAX integer yes"
735 .It "VM\_V\_CACHE\_MIN integer yes"
736 .It "VM\_V\_FREE\_MIN integer yes"
737 .It "VM\_V\_FREE\_RESERVED integer yes"
738 .It "VM\_V\_FREE\_TARGET integer yes"
739 .It "VM\_V\_INACTIVE\_TARGET integer yes"
740 .It "VM\_V\_PAGEOUT\_FREE\_MIN integer yes"
741 .El
742 .Pp
743 .Bl -tag -width 6n
744 .It Li VM_LOADAVG
745 Return the load average history.
746 The returned data consists of a
747 .Va struct loadavg .
748 .It Li VM_METER
749 Return the system wide virtual memory statistics.
750 The returned data consists of a
751 .Va struct vmtotal .
752 .It Li VM_PAGEOUT_ALGORITHM
753 0 if the statistics-based page management algorithm is in use
754 or 1 if the near-LRU algorithm is in use.
755 .It Li VM_SWAPPING_ENABLED
756 1 if process swapping is enabled or 0 if disabled. This variable is
757 permanently set to 0 if the kernel was built with swapping disabled.
758 .It Li VM_V_CACHE_MAX
759 Maximum desired size of the cache queue.
760 .It Li VM_V_CACHE_MIN
761 Minimum desired size of the cache queue. If the cache queue size
762 falls very far below this value, the pageout daemon is awakened.
763 .It Li VM_V_FREE_MIN
764 Minimum amount of memory (cache memory plus free memory)
765 required to be available before a process waiting on memory will be
766 awakened.
767 .It Li VM_V_FREE_RESERVED
768 Processes will awaken the pageout daemon and wait for memory if the
769 number of free and cached pages drops below this value.
770 .It Li VM_V_FREE_TARGET
771 The total amount of free memory (including cache memory) that the
772 pageout daemon tries to maintain.
773 .It Li VM_V_INACTIVE_TARGET
774 The desired number of inactive pages that the pageout daemon should
775 achieve when it runs. Inactive pages can be quickly inserted into
776 process address space when needed.
777 .It Li VM_V_PAGEOUT_FREE_MIN
778 If the amount of free and cache memory falls below this value, the
779 pageout daemon will enter "memory conserving mode" to avoid deadlock.
780 .El
781 .Sh RETURN VALUES
782 .Rv -std
783 .Sh FILES
784 .Bl -tag -width ".In netinet/icmp_var.h" -compact
785 .It In sys/sysctl.h
786 definitions for top level identifiers, second level kernel and hardware
787 identifiers, and user level identifiers
788 .It In sys/socket.h
789 definitions for second level network identifiers
790 .It In sys/gmon.h
791 definitions for third level profiling identifiers
792 .It In vm/vm_param.h
793 definitions for second level virtual memory identifiers
794 .It In netinet/in.h
795 definitions for third level IPv4/IPv6 identifiers and
796 fourth level IPv4/v6 identifiers
797 .It In netinet/icmp_var.h
798 definitions for fourth level ICMP identifiers
799 .It In netinet/icmp6.h
800 definitions for fourth level ICMPv6 identifiers
801 .It In netinet/udp_var.h
802 definitions for fourth level UDP identifiers
803 .El
804 .Sh ERRORS
805 The following errors may be reported:
806 .Bl -tag -width Er
807 .It Bq Er EFAULT
808 The buffer
809 .Fa name ,
810 .Fa oldp ,
811 .Fa newp ,
812 or length pointer
813 .Fa oldlenp
814 contains an invalid address.
815 .It Bq Er EINVAL
816 The
817 .Fa name
818 array is less than two or greater than CTL_MAXNAME.
819 .It Bq Er EINVAL
820 A non-null
821 .Fa newp
822 is given and its specified length in
823 .Fa newlen
824 is too large or too small.
825 .It Bq Er ENOMEM
826 The length pointed to by
827 .Fa oldlenp
828 is too short to hold the requested value.
829 .It Bq Er ENOTDIR
830 The
831 .Fa name
832 array specifies an intermediate rather than terminal name.
833 .It Bq Er EISDIR
834 The
835 .Fa name
836 array specifies a terminal name, but the actual name is not terminal.
837 .It Bq Er ENOENT
838 The
839 .Fa name
840 array specifies a value that is unknown.
841 .It Bq Er EPERM
842 An attempt is made to set a read-only value.
843 .It Bq Er EPERM
844 A process without appropriate privilege attempts to set a value.
845 .El
846 .Sh SEE ALSO
847 .Xr sysconf 3 ,
848 .Xr sysctl 8
849 .Sh HISTORY
850 The
851 .Fn sysctl
852 function first appeared in
853 .Bx 4.4 .