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28 .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95
29 .\" $FreeBSD: src/lib/libc/gen/sysctl.3,v 1.33.2.13 2002/04/07 04:57:14 dd Exp $
38 .Nd get or set system information
45 .Fn sysctl "const int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
47 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
49 .Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep"
53 function retrieves system information and allows processes with
54 appropriate privileges to set system information.
55 The information available from
57 consists of integers, strings, and tables.
58 Information may be retrieved and set from the command interface
63 Unless explicitly noted below,
65 returns a consistent snapshot of the data requested.
66 Consistency is obtained by locking the destination
67 buffer into memory so that the data may be copied out without blocking.
70 are serialized to avoid deadlock.
72 The state is described using a ``Management Information Base'' (MIB)
77 length array of integers.
81 function accepts an ASCII representation of the name and internally
82 looks up the integer name vector. Apart from that, it behaves the same
87 The information is copied into the buffer specified by
89 The size of the buffer is given by the location specified by
92 and that location gives the amount of data copied after a successful call
93 and after a call that returns with the error code
95 If the amount of data available is greater
96 than the size of the buffer supplied,
97 the call supplies as much data as fits in the buffer provided
98 and returns with the error code
100 If the old value is not desired,
104 should be set to NULL.
106 The size of the available data can be determined by calling
108 with a NULL parameter for
110 The size of the available data will be returned in the location pointed to by
112 For some operations, the amount of space may change often.
113 For these operations,
114 the system attempts to round up so that the returned size is
115 large enough for a call to return the data shortly thereafter.
119 is set to point to a buffer of length
121 from which the requested value is to be taken.
122 If a new value is not to be set,
124 should be set to NULL and
130 function accepts an ASCII representation of the name,
131 looks up the integer name vector,
132 and returns the numeric representation in the mib array pointed to by
134 The number of elements in the mib array is given by the location specified by
137 and that location gives the number of entries copied after a successful call.
142 may be used in subsequent
144 calls to get the data associated with the requested ASCII name.
145 This interface is intended for use by applications that want to
146 repeatedly request the same variable (the
148 function runs in about a third the time as the same request made via the
153 function is also useful for fetching mib prefixes and then adding
155 For example, to fetch process information
156 for processes with pid's less than 100:
158 .Bd -literal -offset indent -compact
161 struct kinfo_proc kp;
163 /* Fill out the first three components of the mib */
165 sysctlnametomib("kern.proc.pid", mib, &len);
167 /* Fetch and print entries for pid's < 100 */
168 for (i = 0; i < 100; i++) {
171 if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
178 The top level names are defined with a CTL_ prefix in
181 The next and subsequent levels down are found in the include files
182 listed here, and described in separate sections below.
183 .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
184 .It Sy "Name Next level names Description"
185 .It "CTL\_DEBUG sys/sysctl.h Debugging"
186 .It "CTL\_VFS sys/mount.h Filesystem"
187 .It "CTL\_HW sys/sysctl.h Generic CPU, I/O"
188 .It "CTL\_KERN sys/sysctl.h High kernel limits"
189 .It "CTL\_MACHDEP sys/sysctl.h Machine dependent"
190 .It "CTL\_NET sys/socket.h Networking"
191 .It "CTL\_USER sys/sysctl.h User-level"
192 .It "CTL\_VM vm/vm_param.h Virtual memory"
195 For example, the following retrieves the maximum number of processes allowed
198 .Bd -literal -offset indent -compact
203 mib[1] = KERN_MAXPROC;
204 len = sizeof(maxproc);
205 sysctl(mib, 2, &maxproc, &len, NULL, 0);
208 To retrieve the standard search path for the system utilities:
210 .Bd -literal -offset indent -compact
216 mib[1] = USER_CS_PATH;
217 sysctl(mib, 2, NULL, &len, NULL, 0);
219 sysctl(mib, 2, p, &len, NULL, 0);
222 The debugging variables vary from system to system.
223 A debugging variable may be added or deleted without need to recompile
228 gets the list of debugging variables from the kernel and
229 displays their current values.
230 The system defines twenty
231 .Vt ( struct ctldebug )
236 They are declared as separate variables so that they can be
237 individually initialized at the location of their associated variable.
238 The loader prevents multiple use of the same variable by issuing errors
239 if a variable is initialized in more than one place.
240 For example, to export the variable
242 as a debugging variable, the following declaration would be used:
243 .Bd -literal -offset indent -compact
244 int dospecialcheck = 1;
245 struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
248 A distinguished second level name, VFS_GENERIC,
249 is used to get general information about all filesystems.
250 One of its third level identifiers is VFS_MAXTYPENUM
251 that gives the highest valid filesystem type number.
252 Its other third level identifier is VFS_CONF that
253 returns configuration information about the filesystem
254 type given as a fourth level identifier (see
256 as an example of its use).
257 The remaining second level identifiers are the
258 filesystem type number returned by a
260 call or from VFS_CONF.
261 The third level identifiers available for each filesystem
262 are given in the header file that defines the mount
263 argument structure for that filesystem.
265 The string and integer information available for the CTL_HW level
267 The changeable column shows whether a process with appropriate
268 privilege may change the value.
269 .Bl -column "Second level nameXXXXXX" integerXXX -offset indent
270 .It Sy "Second level name Type Changeable"
271 .It "HW\_MACHINE string no"
272 .It "HW\_MODEL string no"
273 .It "HW\_NCPU integer no"
274 .It "HW\_BYTEORDER integer no"
275 .It "HW\_PHYSMEM integer no"
276 .It "HW\_USERMEM integer no"
277 .It "HW\_PAGESIZE integer no"
278 .It "HW\_FLOATINGPOINT integer no"
279 .It "HW\_MACHINE\_ARCH string no"
280 .\".It "HW\_DISKNAMES integer no"
281 .\".It "HW\_DISKSTATS integer no"
282 .It "HW_SENSORS node not applicable"
292 The byteorder (4,321, or 1,234).
294 The bytes of physical memory.
296 The bytes of non-kernel memory.
298 The software page size.
299 .It Li HW_FLOATINGPOINT
300 Nonzero if the floating point support is in hardware.
301 .It Li HW_MACHINE_ARCH
302 The machine dependent architecture type.
303 .\".It Fa HW_DISKNAMES
304 .\".It Fa HW_DISKSTATS
306 Third level comprises an array of
307 .Vt "struct sensordev"
308 structures containing information about devices
309 that may attach hardware monitoring sensors.
311 Third, fourth and fifth levels together comprise an array of
313 structures containing snapshot readings of hardware monitoring sensors.
314 In such usage, third level indicates the numerical representation
315 of the sensor device name to which the sensor is attached
318 and number shall be matched with the help of
319 .Vt "struct sensordev"
321 fourth level indicates sensor type and
322 fifth level is an ordinal sensor number (unique to
323 the specified sensor type on the specified sensor device).
337 The string and integer information available for the CTL_KERN level
339 The changeable column shows whether a process with appropriate
340 privilege may change the value.
341 The types of data currently available are process information,
342 system vnodes, the open file entries, routing table entries,
343 virtual memory statistics, load average history, and clock rate
345 .Bl -column "KERNXMAXPOSIXLOCKSPERUIDXXX" "struct clockrateXXX" -offset indent
346 .It Sy "Second level name Type Changeable"
347 .It "KERN\_ARGMAX integer no"
348 .It "KERN\_BOOTFILE string yes"
349 .It "KERN\_BOOTTIME struct timeval no"
350 .It "KERN\_CLOCKRATE struct clockinfo no"
351 .It "KERN\_FILE struct file no"
352 .It "KERN\_HOSTID integer yes"
353 .It "KERN\_HOSTNAME string yes"
354 .It "KERN\_JOB\_CONTROL integer no"
355 .It "KERN\_MAXFILES integer yes"
356 .It "KERN\_MAXFILESPERPROC integer yes"
357 .It "KERN\_MAXPOSIXLOCKSPERUID integer yes"
358 .It "KERN\_MAXPROC integer no"
359 .It "KERN\_MAXPROCPERUID integer yes"
360 .It "KERN\_MAXVNODES integer yes"
361 .It "KERN\_NGROUPS integer no"
362 .It "KERN\_NISDOMAINNAME string yes"
363 .It "KERN\_OSRELDATE integer no"
364 .It "KERN\_OSRELEASE string no"
365 .It "KERN\_OSREV integer no"
366 .It "KERN\_OSTYPE string no"
367 .It "KERN\_POSIX1 integer no"
368 .It "KERN\_PROC struct proc no"
369 .It "KERN\_PROF node not applicable"
370 .It "KERN\_QUANTUM integer yes"
371 .It "KERN\_SAVED\_IDS integer no"
372 .It "KERN\_SECURELVL integer raise only"
373 .It "KERN\_UPDATEINTERVAL integer no"
374 .It "KERN\_VERSION string no"
375 .It "KERN\_VNODE struct vnode no"
379 The maximum bytes of argument to
382 The full pathname of the file from which the kernel was loaded.
386 structure is returned.
387 This structure contains the time that the system was booted.
388 .It Li KERN_CLOCKRATE
391 structure is returned.
392 This structure contains the clock, statistics clock and profiling clock
393 frequencies, the number of micro-seconds per hz tick and the skew rate.
395 Return the entire file table.
396 The returned data consists of a single
398 followed by an array of
400 whose size depends on the current number of such objects in the system.
402 Get or set the host id.
404 Get or set the hostname.
405 .It Li KERN_JOB_CONTROL
406 Return 1 if job control is available on this system, otherwise 0.
408 The maximum number of files that may be open in the system.
409 .It Li KERN_MAXFILESPERPROC
410 The maximum number of files that may be open for a single process.
411 This limit only applies to processes with an effective uid of nonzero
412 at the time of the open request.
413 Files that have already been opened are not affected if the limit
414 or the effective uid is changed.
416 The maximum number of concurrent processes the system will allow.
417 .It Li KERN_MAXPROCPERUID
418 The maximum number of concurrent processes the system will allow
419 for a single effective uid.
420 This limit only applies to processes with an effective uid of nonzero
421 at the time of a fork request.
422 Processes that have already been started are not affected if the limit
424 .It Li KERN_MAXVNODES
425 The maximum number of vnodes available on the system.
427 The maximum number of supplemental groups.
428 .It Li KERN_NISDOMAINNAME
429 The name of the current YP/NIS domain.
430 .It Li KERN_OSRELDATE
431 The system release date in YYYYMM format
432 (January 1996 is encoded as 199601).
433 .It Li KERN_OSRELEASE
434 The system release string.
436 The system revision string.
438 The system type string.
442 with which the system
445 Return the entire process table, or a subset of it.
447 .Va struct kinfo_proc
448 structures is returned,
449 whose size depends on the current number of such objects in the system.
450 The third and fourth level names are as follows:
451 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
452 .It "Third level name Fourth level is:"
453 .It "KERN\_PROC\_ALL None"
454 .It "KERN\_PROC\_PID A process ID"
455 .It "KERN\_PROC\_PGRP A process group"
456 .It "KERN\_PROC\_TTY A tty device"
457 .It "KERN\_PROC\_UID A user ID"
458 .It "KERN\_PROC\_RUID A real user ID"
462 .Li KERN_PROC_FLAG_LWP
463 to the third level name signals that information about all
464 light weight processes of the selected processes should be returned.
466 Return profiling information about the kernel.
467 If the kernel is not compiled for profiling,
468 attempts to retrieve any of the KERN_PROF values will
471 The third level names for the string and integer profiling information
473 The changeable column shows whether a process with appropriate
474 privilege may change the value.
475 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
476 .It Sy "Third level name Type Changeable"
477 .It "GPROF\_STATE integer yes"
478 .It "GPROF\_COUNT u_short[\|] yes"
479 .It "GPROF\_FROMS u_short[\|] yes"
480 .It "GPROF\_TOS struct tostruct yes"
481 .It "GPROF\_GMONPARAM struct gmonparam no"
484 The variables are as follows:
487 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
488 is running or stopped.
490 Array of statistical program counter counts.
492 Array indexed by program counter of call-from points.
496 describing destination of calls and their counts.
497 .It Li GPROF_GMONPARAM
498 Structure giving the sizes of the above arrays.
501 The maximum period of time, in microseconds, for which a process is allowed
502 to run without being preempted if other processes are in the run queue.
503 .It Li KERN_SAVED_IDS
504 Returns 1 if saved set-group and saved set-user ID is available.
505 .It Li KERN_SECURELVL
506 The system security level.
507 This level may be raised by processes with appropriate privilege.
508 It may not be lowered.
510 The system version string.
512 Return the entire vnode table.
513 Note, the vnode table is not necessarily a consistent snapshot of
515 The returned data consists of an array whose size depends on the
516 current number of such objects in the system.
517 Each element of the array contains the kernel address of a vnode
519 followed by the vnode itself
523 The set of variables defined is architecture dependent.
524 The following variables are defined for the i386 architecture.
525 .Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent
526 .It Sy "Second level name Type Changeable"
527 .It Li "CPU_CONSDEV dev_t no"
528 .It Li "CPU_ADJKERNTZ int yes"
529 .It Li "CPU_DISRTCSET int yes"
530 .It Li "CPU_BOOTINFO struct bootinfo no"
531 .It Li "CPU_WALLCLOCK int yes"
534 The string and integer information available for the CTL_NET level
536 The changeable column shows whether a process with appropriate
537 privilege may change the value.
538 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
539 .It Sy "Second level name Type Changeable"
540 .It "PF\_ROUTE routing messages no"
541 .It "PF\_INET IPv4 values yes"
542 .It "PF\_INET6 IPv6 values yes"
546 Return the entire routing table or a subset of it.
547 The data is returned as a sequence of routing messages (see
549 for the header file, format and meaning).
550 The length of each message is contained in the message header.
552 The third level name is a protocol number, which is currently always 0.
553 The fourth level name is an address family, which may be set to 0 to
554 select all address families.
555 The fifth and sixth level names are as follows:
556 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
557 .It Sy "Fifth level name Sixth level is:"
558 .It "NET\_RT\_FLAGS rtflags"
559 .It "NET\_RT\_DUMP None"
560 .It "NET\_RT\_IFLIST None"
563 Get or set various global information about the IPv4
564 (Internet Protocol version 4).
565 The third level name is the protocol.
566 The fourth level name is the variable name.
567 The currently defined protocols and names are:
568 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
569 .It Sy "Protocol Variable Type Changeable"
570 .It "icmp bmcastecho integer yes"
571 .It "icmp maskrepl integer yes"
572 .It "ip forwarding integer yes"
573 .It "ip redirect integer yes"
574 .It "ip ttl integer yes"
575 .It "udp checksum integer yes"
578 The variables are as follows:
580 .It Li icmp.bmcastecho
581 Returns 1 if an ICMP echo request to a broadcast or multicast address is
584 Returns 1 if ICMP network mask requests are to be answered.
586 Returns 1 when IP forwarding is enabled for the host,
587 meaning that the host is acting as a router.
589 Returns 1 when ICMP redirects may be sent by the host.
590 This option is ignored unless the host is routing IP packets,
591 and should normally be enabled on all systems.
593 The maximum time-to-live (hop count) value for an IP packet sourced by
595 This value applies to normal transport protocols, not to ICMP.
597 Returns 1 when UDP checksums are being computed and checked.
598 Disabling UDP checksums is strongly discouraged.
600 For variables net.inet.*.ipsec, please refer to
604 Get or set various global information about the IPv6
605 (Internet Protocol version 6).
606 The third level name is the protocol.
607 The fourth level name is the variable name.
609 For variables net.inet6.* please refer to
611 For variables net.inet6.*.ipsec6, please refer to
615 The string and integer information available for the CTL_USER level
617 The changeable column shows whether a process with appropriate
618 privilege may change the value.
619 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
620 .It Sy "Second level name Type Changeable"
621 .It "USER\_BC\_BASE\_MAX integer no"
622 .It "USER\_BC\_DIM\_MAX integer no"
623 .It "USER\_BC\_SCALE\_MAX integer no"
624 .It "USER\_BC\_STRING\_MAX integer no"
625 .It "USER\_COLL\_WEIGHTS\_MAX integer no"
626 .It "USER\_CS\_PATH string no"
627 .It "USER\_EXPR\_NEST\_MAX integer no"
628 .It "USER\_LINE\_MAX integer no"
629 .It "USER\_POSIX2\_CHAR\_TERM integer no"
630 .It "USER\_POSIX2\_C\_BIND integer no"
631 .It "USER\_POSIX2\_C\_DEV integer no"
632 .It "USER\_POSIX2\_FORT\_DEV integer no"
633 .It "USER\_POSIX2\_FORT\_RUN integer no"
634 .It "USER\_POSIX2\_LOCALEDEF integer no"
635 .It "USER\_POSIX2\_SW\_DEV integer no"
636 .It "USER\_POSIX2\_UPE integer no"
637 .It "USER\_POSIX2\_VERSION integer no"
638 .It "USER\_RE\_DUP\_MAX integer no"
639 .It "USER\_STREAM\_MAX integer no"
640 .It "USER\_TZNAME\_MAX integer no"
643 .It Li USER_BC_BASE_MAX
644 The maximum ibase/obase values in the
647 .It Li USER_BC_DIM_MAX
648 The maximum array size in the
651 .It Li USER_BC_SCALE_MAX
652 The maximum scale value in the
655 .It Li USER_BC_STRING_MAX
656 The maximum string length in the
659 .It Li USER_COLL_WEIGHTS_MAX
660 The maximum number of weights that can be assigned to any entry of
661 the LC_COLLATE order keyword in the locale definition file.
663 Return a value for the
665 environment variable that finds all the standard utilities.
666 .It Li USER_EXPR_NEST_MAX
667 The maximum number of expressions that can be nested within
672 The maximum length in bytes of a text-processing utility's input
674 .It Li USER_POSIX2_CHAR_TERM
675 Return 1 if the system supports at least one terminal type capable of
676 all operations described in
679 .It Li USER_POSIX2_C_BIND
680 Return 1 if the system's C-language development facilities support the
681 C-Language Bindings Option, otherwise 0.
682 .It Li USER_POSIX2_C_DEV
683 Return 1 if the system supports the C-Language Development Utilities Option,
685 .It Li USER_POSIX2_FORT_DEV
686 Return 1 if the system supports the FORTRAN Development Utilities Option,
688 .It Li USER_POSIX2_FORT_RUN
689 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
691 .It Li USER_POSIX2_LOCALEDEF
692 Return 1 if the system supports the creation of locales, otherwise 0.
693 .It Li USER_POSIX2_SW_DEV
694 Return 1 if the system supports the Software Development Utilities Option,
696 .It Li USER_POSIX2_UPE
697 Return 1 if the system supports the User Portability Utilities Option,
699 .It Li USER_POSIX2_VERSION
702 with which the system attempts to comply.
703 .It Li USER_RE_DUP_MAX
704 The maximum number of repeated occurrences of a regular expression
705 permitted when using interval notation.
706 .It Li USER_STREAM_MAX
707 The minimum maximum number of streams that a process may have open
709 .It Li USER_TZNAME_MAX
710 The minimum maximum number of types supported for the name of a
714 The string and integer information available for the CTL_VM level
716 The changeable column shows whether a process with appropriate
717 privilege may change the value.
718 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
719 .It Sy "Second level name Type Changeable"
720 .It "VM\_LOADAVG struct loadavg no"
721 .It "VM\_METER struct vmtotal no"
722 .It "VM\_PAGEOUT\_ALGORITHM integer yes"
723 .It "VM\_SWAPPING\_ENABLED integer maybe"
724 .It "VM\_V\_CACHE\_MAX integer yes"
725 .It "VM\_V\_CACHE\_MIN integer yes"
726 .It "VM\_V\_FREE\_MIN integer yes"
727 .It "VM\_V\_FREE\_RESERVED integer yes"
728 .It "VM\_V\_FREE\_TARGET integer yes"
729 .It "VM\_V\_INACTIVE\_TARGET integer yes"
730 .It "VM\_V\_PAGEOUT\_FREE\_MIN integer yes"
734 Return the load average history.
735 The returned data consists of a
738 Return the system wide virtual memory statistics.
739 The returned data consists of a
741 .It Li VM_PAGEOUT_ALGORITHM
742 0 if the statistics-based page management algorithm is in use
743 or 1 if the near-LRU algorithm is in use.
744 .It Li VM_SWAPPING_ENABLED
745 1 if process swapping is enabled or 0 if disabled. This variable is
746 permanently set to 0 if the kernel was built with swapping disabled.
747 .It Li VM_V_CACHE_MAX
748 Maximum desired size of the cache queue.
749 .It Li VM_V_CACHE_MIN
750 Minimum desired size of the cache queue. If the cache queue size
751 falls very far below this value, the pageout daemon is awakened.
753 Minimum amount of memory (cache memory plus free memory)
754 required to be available before a process waiting on memory will be
756 .It Li VM_V_FREE_RESERVED
757 Processes will awaken the pageout daemon and wait for memory if the
758 number of free and cached pages drops below this value.
759 .It Li VM_V_FREE_TARGET
760 The total amount of free memory (including cache memory) that the
761 pageout daemon tries to maintain.
762 .It Li VM_V_INACTIVE_TARGET
763 The desired number of inactive pages that the pageout daemon should
764 achieve when it runs. Inactive pages can be quickly inserted into
765 process address space when needed.
766 .It Li VM_V_PAGEOUT_FREE_MIN
767 If the amount of free and cache memory falls below this value, the
768 pageout daemon will enter "memory conserving mode" to avoid deadlock.
773 .Bl -tag -width ".In netinet/icmp_var.h" -compact
775 definitions for top level identifiers, second level kernel and hardware
776 identifiers, and user level identifiers
778 definitions for second level network identifiers
780 definitions for third level profiling identifiers
782 definitions for second level virtual memory identifiers
784 definitions for third level IPv4/IPv6 identifiers and
785 fourth level IPv4/v6 identifiers
786 .It In netinet/icmp_var.h
787 definitions for fourth level ICMP identifiers
788 .It In netinet/icmp6.h
789 definitions for fourth level ICMPv6 identifiers
790 .It In netinet/udp_var.h
791 definitions for fourth level UDP identifiers
794 The following errors may be reported:
803 contains an invalid address.
807 array is less than two or greater than CTL_MAXNAME.
811 is given and its specified length in
813 is too large or too small.
815 The length pointed to by
817 is too short to hold the requested value.
821 array specifies an intermediate rather than terminal name.
825 array specifies a terminal name, but the actual name is not terminal.
829 array specifies a value that is unknown.
831 An attempt is made to set a read-only value.
833 A process without appropriate privilege attempts to set a value.
841 function first appeared in