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28 .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95
38 .Nd get or set system information
45 .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
47 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "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.
83 Apart from that, it behaves the same
88 The information is copied into the buffer specified by
90 The size of the buffer is given by the location specified by
93 and that location gives the amount of data copied after a successful call
94 and after a call that returns with the error code
96 If the amount of data available is greater
97 than the size of the buffer supplied,
98 the call supplies as much data as fits in the buffer provided
99 and returns with the error code
101 If the old value is not desired,
105 should be set to NULL.
107 The size of the available data can be determined by calling
113 The size of the available data will be returned in the location pointed to by
115 For some operations, the amount of space may change often.
116 For these operations,
117 the system attempts to round up so that the returned size is
118 large enough for a call to return the data shortly thereafter.
122 is set to point to a buffer of length
124 from which the requested value is to be taken.
125 If a new value is not to be set,
127 should be set to NULL and
133 function accepts an ASCII representation of the name,
134 looks up the integer name vector,
135 and returns the numeric representation in the mib array pointed to by
137 The number of elements in the mib array is given by the location specified by
140 and that location gives the number of entries copied after a successful call.
145 may be used in subsequent
147 calls to get the data associated with the requested ASCII name.
148 This interface is intended for use by applications that want to
149 repeatedly request the same variable (the
151 function runs in about a third the time as the same request made via the
156 function is also useful for fetching mib prefixes and then adding
158 For example, to fetch process information
159 for processes with pid's less than 100:
161 .Bd -literal -offset indent -compact
164 struct kinfo_proc kp;
166 /* Fill out the first three components of the mib */
168 sysctlnametomib("kern.proc.pid", mib, &len);
170 /* Fetch and print entries for pid's < 100 */
171 for (i = 0; i < 100; i++) {
174 if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
181 The top level names are defined with a CTL_ prefix in
184 The next and subsequent levels down are found in the include files
185 listed here, and described in separate sections below.
187 .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
188 .It Sy "Name Next level names Description"
189 .It "CTL_DEBUG sys/sysctl.h Debugging"
190 .It "CTL_VFS sys/mount.h File system"
191 .It "CTL_HW sys/sysctl.h Generic CPU, I/O"
192 .It "CTL_KERN sys/sysctl.h High kernel limits"
193 .It "CTL_MACHDEP sys/sysctl.h Machine dependent"
194 .It "CTL_NET sys/socket.h Networking"
195 .It "CTL_USER sys/sysctl.h User-level"
196 .It "CTL_VM vm/vm_param.h Virtual memory"
199 For example, the following retrieves the maximum number of processes allowed
202 .Bd -literal -offset indent -compact
207 mib[1] = KERN_MAXPROC;
208 len = sizeof(maxproc);
209 sysctl(mib, 2, &maxproc, &len, NULL, 0);
212 To retrieve the standard search path for the system utilities:
214 .Bd -literal -offset indent -compact
220 mib[1] = USER_CS_PATH;
221 sysctl(mib, 2, NULL, &len, NULL, 0);
223 sysctl(mib, 2, p, &len, NULL, 0);
226 The debugging variables vary from system to system.
227 A debugging variable may be added or deleted without need to recompile
232 gets the list of debugging variables from the kernel and
233 displays their current values.
234 The system defines twenty
235 .Pq Vt "struct ctldebug"
240 They are declared as separate variables so that they can be
241 individually initialized at the location of their associated variable.
242 The loader prevents multiple use of the same variable by issuing errors
243 if a variable is initialized in more than one place.
244 For example, to export the variable
246 as a debugging variable, the following declaration would be used:
248 .Bd -literal -offset indent -compact
249 int dospecialcheck = 1;
250 struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
253 A distinguished second level name, VFS_GENERIC,
254 is used to get general information about all file systems.
255 One of its third level identifiers is VFS_MAXTYPENUM
256 that gives the highest valid file system type number.
257 Its other third level identifier is VFS_CONF that
258 returns configuration information about the file system
259 type given as a fourth level identifier (see
261 as an example of its use).
262 The remaining second level identifiers are the
263 file system type number returned by a
265 call or from VFS_CONF.
266 The third level identifiers available for each file system
267 are given in the header file that defines the mount
268 argument structure for that file system.
270 The string and integer information available for the CTL_HW level
272 The changeable column shows whether a process with appropriate
273 privilege may change the value.
274 .Bl -column "Second level nameXXXXXX" integerXXX -offset indent
275 .It Sy "Second level name Type Changeable"
276 .It "HW_MACHINE string no"
277 .It "HW_MODEL string no"
278 .It "HW_NCPU integer no"
279 .It "HW_BYTEORDER integer no"
280 .It "HW_PHYSMEM integer no"
281 .It "HW_USERMEM integer no"
282 .It "HW_PAGESIZE integer no"
283 .\".It "HW_DISKNAMES integer no"
284 .\".It "HW_DISKSTATS integer no"
285 .It "HW_FLOATINGPT integer no"
286 .It "HW_MACHINE_ARCH string no"
287 .It "HW_REALMEM integer no"
298 The byteorder (4,321, or 1,234).
300 The bytes of physical memory.
302 The bytes of non-kernel memory.
304 The software page size.
305 .\".It Fa HW_DISKNAMES
306 .\".It Fa HW_DISKSTATS
308 Nonzero if the floating point support is in hardware.
309 .It Li HW_MACHINE_ARCH
310 The machine dependent architecture type.
312 The bytes of real memory.
315 The string and integer information available for the CTL_KERN level
317 The changeable column shows whether a process with appropriate
318 privilege may change the value.
319 The types of data currently available are process information,
320 system vnodes, the open file entries, routing table entries,
321 virtual memory statistics, load average history, and clock rate
323 .Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent
324 .It Sy "Second level name Type Changeable"
325 .It "KERN_ARGMAX integer no"
326 .It "KERN_BOOTFILE string yes"
327 .It "KERN_BOOTTIME struct timeval no"
328 .It "KERN_CLOCKRATE struct clockinfo no"
329 .It "KERN_FILE struct file no"
330 .It "KERN_HOSTID integer yes"
331 .It "KERN_HOSTUUID string yes"
332 .It "KERN_HOSTNAME string yes"
333 .It "KERN_JOB_CONTROL integer no"
334 .It "KERN_MAXFILES integer yes"
335 .It "KERN_MAXFILESPERPROC integer yes"
336 .It "KERN_MAXPROC integer no"
337 .It "KERN_MAXPROCPERUID integer yes"
338 .It "KERN_MAXVNODES integer yes"
339 .It "KERN_NGROUPS integer no"
340 .It "KERN_NISDOMAINNAME string yes"
341 .It "KERN_OSRELDATE integer no"
342 .It "KERN_OSRELEASE string no"
343 .It "KERN_OSREV integer no"
344 .It "KERN_OSTYPE string no"
345 .It "KERN_POSIX1 integer no"
346 .It "KERN_PROC struct proc no"
347 .It "KERN_PROF node not applicable"
348 .It "KERN_QUANTUM integer yes"
349 .It "KERN_SAVED_IDS integer no"
350 .It "KERN_SECURELVL integer raise only"
351 .It "KERN_UPDATEINTERVAL integer no"
352 .It "KERN_VERSION string no"
353 .It "KERN_VNODE struct vnode no"
358 The maximum bytes of argument to
361 The full pathname of the file from which the kernel was loaded.
365 structure is returned.
366 This structure contains the time that the system was booted.
367 .It Li KERN_CLOCKRATE
370 structure is returned.
371 This structure contains the clock, statistics clock and profiling clock
372 frequencies, the number of micro-seconds per hz tick and the skew rate.
374 Return the entire file table.
375 The returned data consists of a single
377 followed by an array of
379 whose size depends on the current number of such objects in the system.
381 Get or set the host ID.
383 Get or set the host's universally unique identifier (UUID).
385 Get or set the hostname.
386 .It Li KERN_JOB_CONTROL
387 Return 1 if job control is available on this system, otherwise 0.
389 The maximum number of files that may be open in the system.
390 .It Li KERN_MAXFILESPERPROC
391 The maximum number of files that may be open for a single process.
392 This limit only applies to processes with an effective uid of nonzero
393 at the time of the open request.
394 Files that have already been opened are not affected if the limit
395 or the effective uid is changed.
397 The maximum number of concurrent processes the system will allow.
398 .It Li KERN_MAXPROCPERUID
399 The maximum number of concurrent processes the system will allow
400 for a single effective uid.
401 This limit only applies to processes with an effective uid of nonzero
402 at the time of a fork request.
403 Processes that have already been started are not affected if the limit
405 .It Li KERN_MAXVNODES
406 The maximum number of vnodes available on the system.
408 The maximum number of supplemental groups.
409 .It Li KERN_NISDOMAINNAME
410 The name of the current YP/NIS domain.
411 .It Li KERN_OSRELDATE
412 The kernel release version in the format
413 .Ar M Ns Ar mm Ns Ar R Ns Ar xx ,
416 is the major version,
418 is the two digit minor version,
420 is 0 if release branch, otherwise 1,
423 is updated when the available APIs change.
425 The userland release version is available from
427 parse this file if you need to get the release version of
428 the currently installed userland.
429 .It Li KERN_OSRELEASE
430 The system release string.
432 The system revision string.
434 The system type string.
438 with which the system
441 Return selected information about specific running processes.
443 For the following names, an array of pairs of
445 followed by corresponding
447 structures is returned,
448 whose size depends on the current number of such objects in the system.
449 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
450 .It "Third level name Fourth level is:"
451 .It "KERN_PROC_ALL None"
452 .It "KERN_PROC_PID A process ID"
453 .It "KERN_PROC_PGRP A process group"
454 .It "KERN_PROC_TTY A tty device"
455 .It "KERN_PROC_UID A user ID"
456 .It "KERN_PROC_RUID A real user ID"
459 If the third level name is
461 then the command line argument
462 array is returned in a flattened form, i.e., zero-terminated arguments
464 The total size of array is returned.
465 It is also possible for a process to set its own process title this way.
466 If the third level name is
467 .Dv KERN_PROC_PATHNAME ,
469 process' text file is stored.
471 .Dv KERN_PROC_PATHNAME ,
474 implies the current process.
475 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
476 .It Sy "Third level name Fourth level is:"
477 .It Dv KERN_PROC_ARGS Ta "A process ID"
478 .It Dv KERN_PROC_PATHNAME Ta "A process ID"
481 Return profiling information about the kernel.
482 If the kernel is not compiled for profiling,
483 attempts to retrieve any of the KERN_PROF values will
486 The third level names for the string and integer profiling information
488 The changeable column shows whether a process with appropriate
489 privilege may change the value.
490 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
491 .It Sy "Third level name Type Changeable"
492 .It "GPROF_STATE integer yes"
493 .It "GPROF_COUNT u_short[\|] yes"
494 .It "GPROF_FROMS u_short[\|] yes"
495 .It "GPROF_TOS struct tostruct yes"
496 .It "GPROF_GMONPARAM struct gmonparam no"
499 The variables are as follows:
502 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
503 is running or stopped.
505 Array of statistical program counter counts.
507 Array indexed by program counter of call-from points.
511 describing destination of calls and their counts.
512 .It Li GPROF_GMONPARAM
513 Structure giving the sizes of the above arrays.
516 The maximum period of time, in microseconds, for which a process is allowed
517 to run without being preempted if other processes are in the run queue.
518 .It Li KERN_SAVED_IDS
519 Returns 1 if saved set-group and saved set-user ID is available.
520 .It Li KERN_SECURELVL
521 The system security level.
522 This level may be raised by processes with appropriate privilege.
523 It may not be lowered.
525 The system version string.
527 Return the entire vnode table.
528 Note, the vnode table is not necessarily a consistent snapshot of
530 The returned data consists of an array whose size depends on the
531 current number of such objects in the system.
532 Each element of the array contains the kernel address of a vnode
534 followed by the vnode itself
538 The string and integer information available for the CTL_NET level
540 The changeable column shows whether a process with appropriate
541 privilege may change the value.
542 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
543 .It Sy "Second level name Type Changeable"
544 .It "PF_ROUTE routing messages no"
545 .It "PF_INET IPv4 values yes"
546 .It "PF_INET6 IPv6 values yes"
551 Return the entire routing table or a subset of it.
552 The data is returned as a sequence of routing messages (see
554 for the header file, format and meaning).
555 The length of each message is contained in the message header.
557 The third level name is a protocol number, which is currently always 0.
558 The fourth level name is an address family, which may be set to 0 to
559 select all address families.
560 The fifth and sixth level names are as follows:
561 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
562 .It Sy "Fifth level name Sixth level is:"
563 .It "NET_RT_FLAGS rtflags"
564 .It "NET_RT_DUMP None"
565 .It "NET_RT_IFLIST 0 or if_index"
566 .It "NET_RT_IFMALIST 0 or if_index"
571 name returns information about multicast group memberships on all interfaces
572 if 0 is specified, or for the interface specified by
575 Get or set various global information about the IPv4
576 (Internet Protocol version 4).
577 The third level name is the protocol.
578 The fourth level name is the variable name.
579 The currently defined protocols and names are:
580 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
581 .It Sy "Protocol Variable Type Changeable"
582 .It "icmp bmcastecho integer yes"
583 .It "icmp maskrepl integer yes"
584 .It "ip forwarding integer yes"
585 .It "ip redirect integer yes"
586 .It "ip ttl integer yes"
587 .It "udp checksum integer yes"
590 The variables are as follows:
592 .It Li icmp.bmcastecho
593 Returns 1 if an ICMP echo request to a broadcast or multicast address is
596 Returns 1 if ICMP network mask requests are to be answered.
598 Returns 1 when IP forwarding is enabled for the host,
599 meaning that the host is acting as a router.
601 Returns 1 when ICMP redirects may be sent by the host.
602 This option is ignored unless the host is routing IP packets,
603 and should normally be enabled on all systems.
605 The maximum time-to-live (hop count) value for an IP packet sourced by
607 This value applies to normal transport protocols, not to ICMP.
609 Returns 1 when UDP checksums are being computed and checked.
610 Disabling UDP checksums is strongly discouraged.
612 For variables net.inet.*.ipsec, please refer to
616 Get or set various global information about the IPv6
617 (Internet Protocol version 6).
618 The third level name is the protocol.
619 The fourth level name is the variable name.
621 For variables net.inet6.* please refer to
623 For variables net.inet6.*.ipsec6, please refer to
627 The string and integer information available for the CTL_USER level
629 The changeable column shows whether a process with appropriate
630 privilege may change the value.
631 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
632 .It Sy "Second level name Type Changeable"
633 .It "USER_BC_BASE_MAX integer no"
634 .It "USER_BC_DIM_MAX integer no"
635 .It "USER_BC_SCALE_MAX integer no"
636 .It "USER_BC_STRING_MAX integer no"
637 .It "USER_COLL_WEIGHTS_MAX integer no"
638 .It "USER_CS_PATH string no"
639 .It "USER_EXPR_NEST_MAX integer no"
640 .It "USER_LINE_MAX integer no"
641 .It "USER_POSIX2_CHAR_TERM integer no"
642 .It "USER_POSIX2_C_BIND integer no"
643 .It "USER_POSIX2_C_DEV integer no"
644 .It "USER_POSIX2_FORT_DEV integer no"
645 .It "USER_POSIX2_FORT_RUN integer no"
646 .It "USER_POSIX2_LOCALEDEF integer no"
647 .It "USER_POSIX2_SW_DEV integer no"
648 .It "USER_POSIX2_UPE integer no"
649 .It "USER_POSIX2_VERSION integer no"
650 .It "USER_RE_DUP_MAX integer no"
651 .It "USER_STREAM_MAX integer no"
652 .It "USER_TZNAME_MAX integer no"
656 .It Li USER_BC_BASE_MAX
657 The maximum ibase/obase values in the
660 .It Li USER_BC_DIM_MAX
661 The maximum array size in the
664 .It Li USER_BC_SCALE_MAX
665 The maximum scale value in the
668 .It Li USER_BC_STRING_MAX
669 The maximum string length in the
672 .It Li USER_COLL_WEIGHTS_MAX
673 The maximum number of weights that can be assigned to any entry of
674 the LC_COLLATE order keyword in the locale definition file.
676 Return a value for the
678 environment variable that finds all the standard utilities.
679 .It Li USER_EXPR_NEST_MAX
680 The maximum number of expressions that can be nested within
685 The maximum length in bytes of a text-processing utility's input
687 .It Li USER_POSIX2_CHAR_TERM
688 Return 1 if the system supports at least one terminal type capable of
689 all operations described in
692 .It Li USER_POSIX2_C_BIND
693 Return 1 if the system's C-language development facilities support the
694 C-Language Bindings Option, otherwise 0.
695 .It Li USER_POSIX2_C_DEV
696 Return 1 if the system supports the C-Language Development Utilities Option,
698 .It Li USER_POSIX2_FORT_DEV
699 Return 1 if the system supports the FORTRAN Development Utilities Option,
701 .It Li USER_POSIX2_FORT_RUN
702 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
704 .It Li USER_POSIX2_LOCALEDEF
705 Return 1 if the system supports the creation of locales, otherwise 0.
706 .It Li USER_POSIX2_SW_DEV
707 Return 1 if the system supports the Software Development Utilities Option,
709 .It Li USER_POSIX2_UPE
710 Return 1 if the system supports the User Portability Utilities Option,
712 .It Li USER_POSIX2_VERSION
715 with which the system attempts to comply.
716 .It Li USER_RE_DUP_MAX
717 The maximum number of repeated occurrences of a regular expression
718 permitted when using interval notation.
719 .It Li USER_STREAM_MAX
720 The minimum maximum number of streams that a process may have open
722 .It Li USER_TZNAME_MAX
723 The minimum maximum number of types supported for the name of a
727 The string and integer information available for the CTL_VM level
729 The changeable column shows whether a process with appropriate
730 privilege may change the value.
731 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
732 .It Sy "Second level name Type Changeable"
733 .It "VM_LOADAVG struct loadavg no"
734 .It "VM_TOTAL struct vmtotal no"
735 .It "VM_PAGEOUT_ALGORITHM integer yes"
736 .It "VM_SWAPPING_ENABLED integer maybe"
737 .It "VM_V_CACHE_MAX integer yes"
738 .It "VM_V_CACHE_MIN integer yes"
739 .It "VM_V_FREE_MIN integer yes"
740 .It "VM_V_FREE_RESERVED integer yes"
741 .It "VM_V_FREE_TARGET integer yes"
742 .It "VM_V_INACTIVE_TARGET integer yes"
743 .It "VM_V_PAGEOUT_FREE_MIN integer yes"
748 Return the load average history.
749 The returned data consists of a
752 Return the system wide virtual memory statistics.
753 The returned data consists of a
755 .It Li VM_PAGEOUT_ALGORITHM
756 0 if the statistics-based page management algorithm is in use
757 or 1 if the near-LRU algorithm is in use.
758 .It Li VM_SWAPPING_ENABLED
759 1 if process swapping is enabled or 0 if disabled.
761 permanently set to 0 if the kernel was built with swapping disabled.
762 .It Li VM_V_CACHE_MAX
763 Maximum desired size of the cache queue.
764 .It Li VM_V_CACHE_MIN
765 Minimum desired size of the cache queue.
766 If the cache queue size
767 falls very far below this value, the pageout daemon is awakened.
769 Minimum amount of memory (cache memory plus free memory)
770 required to be available before a process waiting on memory will be
772 .It Li VM_V_FREE_RESERVED
773 Processes will awaken the pageout daemon and wait for memory if the
774 number of free and cached pages drops below this value.
775 .It Li VM_V_FREE_TARGET
776 The total amount of free memory (including cache memory) that the
777 pageout daemon tries to maintain.
778 .It Li VM_V_INACTIVE_TARGET
779 The desired number of inactive pages that the pageout daemon should
780 achieve when it runs.
781 Inactive pages can be quickly inserted into
782 process address space when needed.
783 .It Li VM_V_PAGEOUT_FREE_MIN
784 If the amount of free and cache memory falls below this value, the
785 pageout daemon will enter "memory conserving mode" to avoid deadlock.
790 .Bl -tag -width <netinet/icmpXvar.h> -compact
792 definitions for top level identifiers, second level kernel and hardware
793 identifiers, and user level identifiers
795 definitions for second level network identifiers
797 definitions for third level profiling identifiers
799 definitions for second level virtual memory identifiers
801 definitions for third level IPv4/IPv6 identifiers and
802 fourth level IPv4/v6 identifiers
803 .It In netinet/icmp_var.h
804 definitions for fourth level ICMP identifiers
805 .It In netinet/icmp6.h
806 definitions for fourth level ICMPv6 identifiers
807 .It In netinet/udp_var.h
808 definitions for fourth level UDP identifiers
811 The following errors may be reported:
820 contains an invalid address.
824 array is less than two or greater than CTL_MAXNAME.
828 is given and its specified length in
830 is too large or too small.
832 The length pointed to by
834 is too short to hold the requested value.
836 The smaller of either the length pointed to by
838 or the estimated size of the returned data exceeds the
839 system limit on locked memory.
843 or a portion of the buffer if the estimated size of the data
844 to be returned is smaller,
845 would cause the process to exceed its per-process locked memory limit.
849 array specifies an intermediate rather than terminal name.
853 array specifies a terminal name, but the actual name is not terminal.
857 array specifies a value that is unknown.
859 An attempt is made to set a read-only value.
861 A process without appropriate privilege attempts to set a value.
869 function first appeared in