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32 .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95
33 .\" $FreeBSD: src/lib/libc/gen/sysctl.3,v 1.63 2004/07/02 23:52:10 ru Exp $
34 .\"
35 .Dd January 23, 2001
36 .Dt SYSCTL 3
37 .Os
38 .Sh NAME
39 .Nm sysctl ,
40 .Nm sysctlbyname ,
41 .Nm sysctlnametomib
42 .Nd get or set system information
43 .Sh LIBRARY
44 .Lb libc
45 .Sh SYNOPSIS
46 .In sys/types.h
47 .In sys/sysctl.h
48 .Ft int
49 .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
50 .Ft int
51 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
52 .Ft int
53 .Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep"
54 .Sh DESCRIPTION
55 The
56 .Fn sysctl
57 function retrieves system information and allows processes with
58 appropriate privileges to set system information.
59 The information available from
60 .Fn sysctl
61 consists of integers, strings, and tables.
62 Information may be retrieved and set from the command interface
63 using the
64 .Xr sysctl 8
65 utility.
66 .Pp
67 Unless explicitly noted below,
68 .Fn sysctl
69 returns a consistent snapshot of the data requested.
70 Consistency is obtained by locking the destination
71 buffer into memory so that the data may be copied out without blocking.
72 Calls to
73 .Fn sysctl
74 are serialized to avoid deadlock.
75 .Pp
76 The state is described using a ``Management Information Base'' (MIB)
77 style name, listed in
78 .Fa name ,
79 which is a
80 .Fa namelen
81 length array of integers.
82 .Pp
83 The
84 .Fn sysctlbyname
85 function accepts an ASCII representation of the name and internally
86 looks up the integer name vector.
87 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 the
114 .Dv NULL
115 argument for
116 .Fa oldp .
117 The size of the available data will be returned in the location pointed to by
118 .Fa oldlenp .
119 For some operations, the amount of space may change often.
120 For these operations,
121 the system attempts to round up so that the returned size is
122 large enough for a call to return the data shortly thereafter.
123 .Pp
124 To set a new value,
125 .Fa newp
126 is set to point to a buffer of length
127 .Fa newlen
128 from which the requested value is to be taken.
129 If a new value is not to be set,
130 .Fa newp
131 should be set to NULL and
132 .Fa newlen
133 set to 0.
134 .Pp
135 The
136 .Fn sysctlnametomib
137 function accepts an ASCII representation of the name,
138 looks up the integer name vector,
139 and returns the numeric representation in the mib array pointed to by
140 .Fa mibp .
141 The number of elements in the mib array is given by the location specified by
142 .Fa sizep
143 before the call,
144 and that location gives the number of entries copied after a successful call.
145 The resulting
146 .Fa mib
147 and
148 .Fa size
149 may be used in subsequent
150 .Fn sysctl
151 calls to get the data associated with the requested ASCII name.
152 This interface is intended for use by applications that want to
153 repeatedly request the same variable (the
154 .Fn sysctl
155 function runs in about a third the time as the same request made via the
156 .Fn sysctlbyname
157 function).
158 The
159 .Fn sysctlnametomib
160 function is also useful for fetching mib prefixes and then adding
161 a final component.
162 For example, to fetch process information
163 for processes with pid's less than 100:
164 .Pp
165 .Bd -literal -offset indent -compact
166 int i, mib[4];
167 size_t len;
168 struct kinfo_proc kp;
169
170 /* Fill out the first three components of the mib */
171 len = 4;
172 sysctlnametomib("kern.proc.pid", mib, &len);
173
174 /* Fetch and print entries for pid's < 100 */
175 for (i = 0; i < 100; i++) {
176 mib[3] = i;
177 len = sizeof(kp);
178 if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
179 perror("sysctl");
180 else if (len > 0)
181 printkproc(&kp);
182 }
183 .Ed
184 .Pp
185 The top level names are defined with a CTL_ prefix in
186 .In sys/sysctl.h ,
187 and are as follows.
188 The next and subsequent levels down are found in the include files
189 listed here, and described in separate sections below.
190 .Pp
191 .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
192 .It Sy "Name Next level names Description"
193 .It "CTL_DEBUG sys/sysctl.h Debugging"
194 .It "CTL_VFS sys/mount.h File system"
195 .It "CTL_HW sys/sysctl.h Generic CPU, I/O"
196 .It "CTL_KERN sys/sysctl.h High kernel limits"
197 .It "CTL_MACHDEP sys/sysctl.h Machine dependent"
198 .It "CTL_NET sys/socket.h Networking"
199 .It "CTL_USER sys/sysctl.h User-level"
200 .It "CTL_VM vm/vm_param.h Virtual memory"
201 .El
202 .Pp
203 For example, the following retrieves the maximum number of processes allowed
204 in the system:
205 .Pp
206 .Bd -literal -offset indent -compact
207 int mib[2], maxproc;
208 size_t len;
209
210 mib[0] = CTL_KERN;
211 mib[1] = KERN_MAXPROC;
212 len = sizeof(maxproc);
213 sysctl(mib, 2, &maxproc, &len, NULL, 0);
214 .Ed
215 .Pp
216 To retrieve the standard search path for the system utilities:
217 .Pp
218 .Bd -literal -offset indent -compact
219 int mib[2];
220 size_t len;
221 char *p;
222
223 mib[0] = CTL_USER;
224 mib[1] = USER_CS_PATH;
225 sysctl(mib, 2, NULL, &len, NULL, 0);
226 p = malloc(len);
227 sysctl(mib, 2, p, &len, NULL, 0);
228 .Ed
229 .Ss CTL_DEBUG
230 The debugging variables vary from system to system.
231 A debugging variable may be added or deleted without need to recompile
232 .Fn sysctl
233 to know about it.
234 Each time it runs,
235 .Fn sysctl
236 gets the list of debugging variables from the kernel and
237 displays their current values.
238 The system defines twenty
239 .Pq Vt "struct ctldebug"
240 variables named
241 .Va debug0
242 through
243 .Va debug19 .
244 They are declared as separate variables so that they can be
245 individually initialized at the location of their associated variable.
246 The loader prevents multiple use of the same variable by issuing errors
247 if a variable is initialized in more than one place.
248 For example, to export the variable
249 .Va dospecialcheck
250 as a debugging variable, the following declaration would be used:
251 .Pp
252 .Bd -literal -offset indent -compact
253 int dospecialcheck = 1;
254 struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
255 .Ed
256 .Ss CTL_VFS
257 A distinguished second level name, VFS_GENERIC,
258 is used to get general information about all file systems.
259 One of its third level identifiers is VFS_MAXTYPENUM
260 that gives the highest valid file system type number.
261 Its other third level identifier is VFS_CONF that
262 returns configuration information about the file system
263 type given as a fourth level identifier (see
264 .Xr getvfsbyname 3
265 as an example of its use).
266 The remaining second level identifiers are the
267 file system type number returned by a
268 .Xr statfs 2
269 call or from VFS_CONF.
270 The third level identifiers available for each file system
271 are given in the header file that defines the mount
272 argument structure for that file system.
273 .Ss CTL_HW
274 The string and integer information available for the CTL_HW level
275 is detailed below.
276 The changeable column shows whether a process with appropriate
277 privilege may change the value.
278 .Bl -column "Second level nameXXXXXX" integerXXX -offset indent
279 .It Sy "Second level name Type Changeable"
280 .It "HW_MACHINE string no"
281 .It "HW_MODEL string no"
282 .It "HW_NCPU integer no"
283 .It "HW_BYTEORDER integer no"
284 .It "HW_PHYSMEM integer no"
285 .It "HW_MEMSIZE integer no"
286 .It "HW_USERMEM integer no"
287 .It "HW_PAGESIZE integer no"
288 .It "HW_FLOATINGPOINT integer no"
289 .It "HW_MACHINE_ARCH string no"
290 .\".It "HW_DISKNAMES integer no"
291 .\".It "HW_DISKSTATS integer no"
292 .El
293 .Pp
294 .Bl -tag -width 6n
295 .It Li HW_MACHINE
296 The machine class.
297 .It Li HW_MODEL
298 The machine model
299 .It Li HW_NCPU
300 The number of cpus.
301 .It Li HW_BYTEORDER
302 The byteorder (4,321, or 1,234).
303 .It Li HW_PHYSMEM
304 The bytes of physical memory represented by a 32-bit integer (for backward compatibility). Use HW_MEMSIZE instead.
305 .It Li HW_MEMSIZE
306 The bytes of physical memory represented by a 64-bit integer.
307 .It Li HW_USERMEM
308 The bytes of non-kernel memory.
309 .It Li HW_PAGESIZE
310 The software page size.
311 .It Li HW_FLOATINGPOINT
312 Nonzero if the floating point support is in hardware.
313 .It Li HW_MACHINE_ARCH
314 The machine dependent architecture type.
315 .\".It Fa HW_DISKNAMES
316 .\".It Fa HW_DISKSTATS
317 .El
318 .Ss CTL_KERN
319 The string and integer information available for the CTL_KERN level
320 is detailed below.
321 The changeable column shows whether a process with appropriate
322 privilege may change the value.
323 The types of data currently available are process information,
324 system vnodes, the open file entries, routing table entries,
325 virtual memory statistics, load average history, and clock rate
326 information.
327 .Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent
328 .It Sy "Second level name Type Changeable"
329 .It "KERN_ARGMAX integer no"
330 .It "KERN_BOOTFILE string yes"
331 .It "KERN_BOOTTIME struct timeval no"
332 .It "KERN_CLOCKRATE struct clockinfo no"
333 .It "KERN_FILE struct file no"
334 .It "KERN_HOSTID integer yes"
335 .It "KERN_HOSTNAME string yes"
336 .It "KERN_JOB_CONTROL integer no"
337 .It "KERN_MAXFILES integer yes"
338 .It "KERN_MAXFILESPERPROC integer yes"
339 .It "KERN_MAXPROC integer no"
340 .It "KERN_MAXPROCPERUID integer yes"
341 .It "KERN_MAXVNODES integer yes"
342 .It "KERN_NGROUPS integer no"
343 .It "KERN_NISDOMAINNAME string yes"
344 .It "KERN_OSRELDATE integer no"
345 .It "KERN_OSRELEASE string no"
346 .It "KERN_OSREV integer no"
347 .It "KERN_OSTYPE string no"
348 .It "KERN_POSIX1 integer no"
349 .It "KERN_PROC struct proc no"
350 .It "KERN_PROF node not applicable"
351 .It "KERN_QUANTUM integer yes"
352 .It "KERN_SAVED_IDS integer no"
353 .It "KERN_SECURELVL integer raise only"
354 .It "KERN_UPDATEINTERVAL integer no"
355 .It "KERN_VERSION string no"
356 .It "KERN_VNODE struct vnode no"
357 .El
358 .Pp
359 .Bl -tag -width 6n
360 .It Li KERN_ARGMAX
361 The maximum bytes of argument to
362 .Xr execve 2 .
363 .It Li KERN_BOOTFILE
364 The full pathname of the file from which the kernel was loaded.
365 .It Li KERN_BOOTTIME
366 A
367 .Va struct timeval
368 structure is returned.
369 This structure contains the time that the system was booted.
370 .It Li KERN_CLOCKRATE
371 A
372 .Va struct clockinfo
373 structure is returned.
374 This structure contains the clock, statistics clock and profiling clock
375 frequencies, the number of micro-seconds per hz tick and the skew rate.
376 .It Li KERN_FILE
377 Return the entire file table.
378 The returned data consists of a single
379 .Va struct filehead
380 followed by an array of
381 .Va struct file ,
382 whose size depends on the current number of such objects in the system.
383 .It Li KERN_HOSTID
384 Get or set the host id.
385 .It Li KERN_HOSTNAME
386 Get or set the hostname.
387 .It Li KERN_JOB_CONTROL
388 Return 1 if job control is available on this system, otherwise 0.
389 .It Li KERN_MAXFILES
390 The maximum number of files that may be open in the system.
391 .It Li KERN_MAXFILESPERPROC
392 The maximum number of files that may be open for a single process.
393 This limit only applies to processes with an effective uid of nonzero
394 at the time of the open request.
395 Files that have already been opened are not affected if the limit
396 or the effective uid is changed.
397 .It Li KERN_MAXPROC
398 The maximum number of concurrent processes the system will allow.
399 .It Li KERN_MAXPROCPERUID
400 The maximum number of concurrent processes the system will allow
401 for a single effective uid.
402 This limit only applies to processes with an effective uid of nonzero
403 at the time of a fork request.
404 Processes that have already been started are not affected if the limit
405 is changed.
406 .It Li KERN_MAXVNODES
407 The maximum number of vnodes available on the system.
408 .It Li KERN_NGROUPS
409 The maximum number of supplemental groups.
410 .It Li KERN_NISDOMAINNAME
411 The name of the current YP/NIS domain.
412 .It Li KERN_OSRELDATE
413 The kernel release version in the format
414 .Ar M Ns Ar mm Ns Ar R Ns Ar xx ,
415 where
416 .Ar M
417 is the major version,
418 .Ar mm
419 is the two digit minor version,
420 .Ar R
421 is 0 if release branch, otherwise 1,
422 and
423 .Ar xx
424 is updated when the available APIs change.
425 .Pp
426 The userland release version is available from
427 .In osreldate.h ;
428 parse this file if you need to get the release version of
429 the currently installed userland.
430 .It Li KERN_OSRELEASE
431 The system release string.
432 .It Li KERN_OSREV
433 The system revision string.
434 .It Li KERN_OSTYPE
435 The system type string.
436 .It Li KERN_POSIX1
437 The version of
438 .St -p1003.1
439 with which the system
440 attempts to comply.
441 .It Li KERN_PROC
442 Return the entire process table, or a subset of it.
443 An array of pairs of
444 .Va struct proc
445 followed by corresponding
446 .Va struct eproc
447 structures is returned,
448 whose size depends on the current number of such objects in the system.
449 The third and fourth level names are as follows:
450 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
451 .It "Third level name Fourth level is:"
452 .It "KERN_PROC_ALL None"
453 .It "KERN_PROC_PID A process ID"
454 .It "KERN_PROC_PGRP A process group"
455 .It "KERN_PROC_TTY A tty device"
456 .It "KERN_PROC_UID A user ID"
457 .It "KERN_PROC_RUID A real user ID"
458 .El
459 .Pp
460 If the third level name is KERN_PROC_ARGS then the command line argument
461 array is returned in a flattened form, i.e., zero-terminated arguments
462 follow each other.
463 The total size of array is returned.
464 It is also possible for a process to set its own process title this way.
465 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
466 .It Sy "Third level name Fourth level is:"
467 .It "KERN_PROC_ARGS A process ID"
468 .El
469 .It Li KERN_PROF
470 Return profiling information about the kernel.
471 If the kernel is not compiled for profiling,
472 attempts to retrieve any of the KERN_PROF values will
473 fail with
474 .Er ENOENT .
475 The third level names for the string and integer profiling information
476 is detailed below.
477 The changeable column shows whether a process with appropriate
478 privilege may change the value.
479 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
480 .It Sy "Third level name Type Changeable"
481 .It "GPROF_STATE integer yes"
482 .It "GPROF_COUNT u_short[\|] yes"
483 .It "GPROF_FROMS u_short[\|] yes"
484 .It "GPROF_TOS struct tostruct yes"
485 .It "GPROF_GMONPARAM struct gmonparam no"
486 .El
487 .Pp
488 The variables are as follows:
489 .Bl -tag -width 6n
490 .It Li GPROF_STATE
491 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
492 is running or stopped.
493 .It Li GPROF_COUNT
494 Array of statistical program counter counts.
495 .It Li GPROF_FROMS
496 Array indexed by program counter of call-from points.
497 .It Li GPROF_TOS
498 Array of
499 .Va struct tostruct
500 describing destination of calls and their counts.
501 .It Li GPROF_GMONPARAM
502 Structure giving the sizes of the above arrays.
503 .El
504 .It Li KERN_QUANTUM
505 The maximum period of time, in microseconds, for which a process is allowed
506 to run without being preempted if other processes are in the run queue.
507 .It Li KERN_SAVED_IDS
508 Returns 1 if saved set-group and saved set-user ID is available.
509 .It Li KERN_SECURELVL
510 The system security level.
511 This level may be raised by processes with appropriate privilege.
512 It may not be lowered.
513 .It Li KERN_VERSION
514 The system version string.
515 .It Li KERN_VNODE
516 Return the entire vnode table.
517 Note, the vnode table is not necessarily a consistent snapshot of
518 the system.
519 The returned data consists of an array whose size depends on the
520 current number of such objects in the system.
521 Each element of the array contains the kernel address of a vnode
522 .Va struct vnode *
523 followed by the vnode itself
524 .Va struct vnode .
525 .El
526 .Ss CTL_MACHDEP
527 The set of variables defined is architecture dependent.
528 The following variables are defined for the i386 architecture.
529 .Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent
530 .It Sy "Second level name Type Changeable"
531 .It Li "CPU_CONSDEV dev_t no"
532 .It Li "CPU_ADJKERNTZ int yes"
533 .It Li "CPU_DISRTCSET int yes"
534 .It Li "CPU_BOOTINFO struct bootinfo no"
535 .It Li "CPU_WALLCLOCK int yes"
536 .El
537 .Ss CTL_NET
538 The string and integer information available for the CTL_NET level
539 is detailed below.
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"
547 .El
548 .Pp
549 .Bl -tag -width 6n
550 .It Li PF_ROUTE
551 Return the entire routing table or a subset of it.
552 The data is returned as a sequence of routing messages (see
553 .Xr route 4
554 for the header file, format and meaning).
555 The length of each message is contained in the message header.
556 .Pp
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"
567 .El
568 .Pp
569 The
570 .Dv NET_RT_IFMALIST
571 name returns information about multicast group memberships on all interfaces
572 if 0 is specified, or for the interface specified by
573 .Va if_index .
574 .It Li PF_INET
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"
588 .El
589 .Pp
590 The variables are as follows:
591 .Bl -tag -width 6n
592 .It Li icmp.bmcastecho
593 Returns 1 if an ICMP echo request to a broadcast or multicast address is
594 to be answered.
595 .It Li icmp.maskrepl
596 Returns 1 if ICMP network mask requests are to be answered.
597 .It Li ip.forwarding
598 Returns 1 when IP forwarding is enabled for the host,
599 meaning that the host is acting as a router.
600 .It Li ip.redirect
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.
604 .It Li ip.ttl
605 The maximum time-to-live (hop count) value for an IP packet sourced by
606 the system.
607 This value applies to normal transport protocols, not to ICMP.
608 .It Li udp.checksum
609 Returns 1 when UDP checksums are being computed and checked.
610 Disabling UDP checksums is strongly discouraged.
611 .Pp
612 For variables net.inet.*.ipsec, please refer to
613 .Xr ipsec 4 .
614 .El
615 .It Li PF_INET6
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.
620 .Pp
621 For variables net.inet6.* please refer to
622 .Xr inet6 4 .
623 For variables net.inet6.*.ipsec6, please refer to
624 .Xr ipsec 4 .
625 .El
626 .Ss CTL_USER
627 The string and integer information available for the CTL_USER level
628 is detailed below.
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"
653 .El
654 .Bl -tag -width 6n
655 .Pp
656 .It Li USER_BC_BASE_MAX
657 The maximum ibase/obase values in the
658 .Xr bc 1
659 utility.
660 .It Li USER_BC_DIM_MAX
661 The maximum array size in the
662 .Xr bc 1
663 utility.
664 .It Li USER_BC_SCALE_MAX
665 The maximum scale value in the
666 .Xr bc 1
667 utility.
668 .It Li USER_BC_STRING_MAX
669 The maximum string length in the
670 .Xr bc 1
671 utility.
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.
675 .It Li USER_CS_PATH
676 Return a value for the
677 .Ev PATH
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
681 parenthesis by the
682 .Xr expr 1
683 utility.
684 .It Li USER_LINE_MAX
685 The maximum length in bytes of a text-processing utility's input
686 line.
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
690 .St -p1003.2 ,
691 otherwise 0.
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,
697 otherwise 0.
698 .It Li USER_POSIX2_FORT_DEV
699 Return 1 if the system supports the FORTRAN Development Utilities Option,
700 otherwise 0.
701 .It Li USER_POSIX2_FORT_RUN
702 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
703 otherwise 0.
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,
708 otherwise 0.
709 .It Li USER_POSIX2_UPE
710 Return 1 if the system supports the User Portability Utilities Option,
711 otherwise 0.
712 .It Li USER_POSIX2_VERSION
713 The version of
714 .St -p1003.2
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
721 at any one time.
722 .It Li USER_TZNAME_MAX
723 The minimum maximum number of types supported for the name of a
724 timezone.
725 .El
726 .Ss CTL_VM
727 The string and integer information available for the CTL_VM level
728 is detailed below.
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_METER 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"
744 .El
745 .Pp
746 .Bl -tag -width 6n
747 .It Li VM_LOADAVG
748 Return the load average history.
749 The returned data consists of a
750 .Va struct loadavg .
751 .It Li VM_METER
752 Return the system wide virtual memory statistics.
753 The returned data consists of a
754 .Va struct vmtotal .
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.
760 This variable is
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.
768 .It Li VM_V_FREE_MIN
769 Minimum amount of memory (cache memory plus free memory)
770 required to be available before a process waiting on memory will be
771 awakened.
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.
786 .El
787 .Sh RETURN VALUES
788 .Rv -std
789 .Sh ERRORS
790 The following errors may be reported:
791 .Bl -tag -width Er
792 .It Bq Er EFAULT
793 The buffer
794 .Fa name ,
795 .Fa oldp ,
796 .Fa newp ,
797 or length pointer
798 .Fa oldlenp
799 contains an invalid address.
800 .It Bq Er EINVAL
801 The
802 .Fa name
803 array is less than two or greater than CTL_MAXNAME.
804 .It Bq Er EINVAL
805 A non-null
806 .Fa newp
807 is given and its specified length in
808 .Fa newlen
809 is too large or too small.
810 .It Bq Er ENOMEM
811 The length pointed to by
812 .Fa oldlenp
813 is too short to hold the requested value.
814 .It Bq Er ENOMEM
815 The smaller of either the length pointed to by
816 .Fa oldlenp
817 or the estimated size of the returned data exceeds the
818 system limit on locked memory.
819 .It Bq Er ENOMEM
820 Locking the buffer
821 .Fa oldp ,
822 or a portion of the buffer if the estimated size of the data
823 to be returned is smaller,
824 would cause the process to exceed its per-process locked memory limit.
825 .It Bq Er ENOTDIR
826 The
827 .Fa name
828 array specifies an intermediate rather than terminal name.
829 .It Bq Er EISDIR
830 The
831 .Fa name
832 array specifies a terminal name, but the actual name is not terminal.
833 .It Bq Er ENOENT
834 The
835 .Fa name
836 array specifies a value that is unknown.
837 .It Bq Er EPERM
838 An attempt is made to set a read-only value.
839 .It Bq Er EPERM
840 A process without appropriate privilege attempts to set a value.
841 .El
842 .Sh FILES
843 .Bl -tag -width <netinet/icmpXvar.h> -compact
844 .It In sys/sysctl.h
845 definitions for top level identifiers, second level kernel and hardware
846 identifiers, and user level identifiers
847 .It In sys/socket.h
848 definitions for second level network identifiers
849 .It In sys/gmon.h
850 definitions for third level profiling identifiers
851 .It In vm/vm_param.h
852 definitions for second level virtual memory identifiers
853 .It In netinet/in.h
854 definitions for third level IPv4/IPv6 identifiers and
855 fourth level IPv4/v6 identifiers
856 .It In netinet/icmp_var.h
857 definitions for fourth level ICMP identifiers
858 .It In netinet/icmp6.h
859 definitions for fourth level ICMPv6 identifiers
860 .It In netinet/udp_var.h
861 definitions for fourth level UDP identifiers
862 .El
863 .Sh SEE ALSO
864 .Xr sysconf 3 ,
865 .Xr sysctl 8
866 .Sh HISTORY
867 The
868 .Fn sysctl
869 function first appeared in
870 .Bx 4.4 .