1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95 33.\" $FreeBSD$ 34.\" 35.Dd May 9, 1995 36.Dt SYSCTL 3 37.Os 38.Sh NAME 39.Nm sysctl , 40.Nm sysctlbyname 41.Nd get or set system information 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include <sys/types.h> 46.Fd #include <sys/sysctl.h> 47.Ft int 48.Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen" 49.Ft int 50.Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen" 51.Sh DESCRIPTION 52The 53.Fn sysctl 54function retrieves system information and allows processes with 55appropriate privileges to set system information. 56The information available from 57.Fn sysctl 58consists of integers, strings, and tables. 59Information may be retrieved and set from the command interface 60using the 61.Xr sysctl 8 62utility. 63.Pp 64Unless explicitly noted below, 65.Fn sysctl 66returns a consistent snapshot of the data requested. 67Consistency is obtained by locking the destination 68buffer into memory so that the data may be copied out without blocking. 69Calls to 70.Fn sysctl 71are serialized to avoid deadlock. 72.Pp 73The state is described using a ``Management Information Base'' (MIB) 74style name, listed in 75.Fa name , 76which is a 77.Fa namelen 78length array of integers. 79.Pp 80The 81.Fn sysctlbyname 82function accepts an ASCII representation of the name and internally 83looks up the integer name vector. Apart from that, it behaves the same 84as the standard 85.Fn sysctl 86function. 87.Pp 88The information is copied into the buffer specified by 89.Fa oldp . 90The size of the buffer is given by the location specified by 91.Fa oldlenp 92before the call, 93and that location gives the amount of data copied after a successful call 94and after a call that returns with the error code ENOMEM. 95If the amount of data available is greater 96than the size of the buffer supplied, 97the call supplies as much data as fits in the buffer provided 98and returns with the error code ENOMEM. 99If the old value is not desired, 100.Fa oldp 101and 102.Fa oldlenp 103should be set to NULL. 104.Pp 105The size of the available data can be determined by calling 106.Fn sysctl 107with a NULL parameter for 108.Fa oldp . 109The size of the available data will be returned in the location pointed to by 110.Fa oldlenp . 111For some operations, the amount of space may change often. 112For these operations, 113the system attempts to round up so that the returned size is 114large enough for a call to return the data shortly thereafter. 115.Pp 116To set a new value, 117.Fa newp 118is set to point to a buffer of length 119.Fa newlen 120from which the requested value is to be taken. 121If a new value is not to be set, 122.Fa newp 123should be set to NULL and 124.Fa newlen 125set to 0. 126.Pp 127The top level names are defined with a CTL_ prefix in 128.Aq Pa sys/sysctl.h , 129and are as follows. 130The next and subsequent levels down are found in the include files 131listed here, and described in separate sections below. 132.Pp 133.Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent 134.It Sy Pa Name Next level names Description 135.It CTL\_DEBUG sys/sysctl.h Debugging 136.It CTL\_VFS sys/mount.h Filesystem 137.It CTL\_HW sys/sysctl.h Generic CPU, I/O 138.It CTL\_KERN sys/sysctl.h High kernel limits 139.It CTL\_MACHDEP sys/sysctl.h Machine dependent 140.It CTL\_NET sys/socket.h Networking 141.It CTL\_USER sys/sysctl.h User-level 142.It CTL\_VM vm/vm_param.h Virtual memory 143.El 144.Pp 145For example, the following retrieves the maximum number of processes allowed 146in the system: 147.Pp 148.Bd -literal -offset indent -compact 149int mib[2], maxproc; 150size_t len; 151 152mib[0] = CTL_KERN; 153mib[1] = KERN_MAXPROC; 154len = sizeof(maxproc); 155sysctl(mib, 2, &maxproc, &len, NULL, 0); 156.Ed 157.Pp 158To retrieve the standard search path for the system utilities: 159.Pp 160.Bd -literal -offset indent -compact 161int mib[2]; 162size_t len; 163char *p; 164 165mib[0] = CTL_USER; 166mib[1] = USER_CS_PATH; 167sysctl(mib, 2, NULL, &len, NULL, 0); 168p = malloc(len); 169sysctl(mib, 2, p, &len, NULL, 0); 170.Ed 171.Ss CTL_DEBUG 172The debugging variables vary from system to system. 173A debugging variable may be added or deleted without need to recompile 174.Fn sysctl 175to know about it. 176Each time it runs, 177.Fn sysctl 178gets the list of debugging variables from the kernel and 179displays their current values. 180The system defines twenty 181.Ns ( Va struct ctldebug ) 182variables named 183.Nm debug0 184through 185.Nm debug19 . 186They are declared as separate variables so that they can be 187individually initialized at the location of their associated variable. 188The loader prevents multiple use of the same variable by issuing errors 189if a variable is initialized in more than one place. 190For example, to export the variable 191.Nm dospecialcheck 192as a debugging variable, the following declaration would be used: 193.Bd -literal -offset indent -compact 194int dospecialcheck = 1; 195struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; 196.Ed 197.Ss CTL_VFS 198A distinguished second level name, VFS_GENERIC, 199is used to get general information about all filesystems. 200One of its third level identifiers is VFS_MAXTYPENUM 201that gives the highest valid filesystem type number. 202Its other third level identifier is VFS_CONF that 203returns configuration information about the filesystem 204type given as a fourth level identifier (see 205.Xr getvfsbyname 3 206as an example of its use). 207The remaining second level identifiers are the 208filesystem type number returned by a 209.Xr statfs 2 210call or from VFS_CONF. 211The third level identifiers available for each filesystem 212are given in the header file that defines the mount 213argument structure for that filesystem. 214.Ss CTL_HW 215The string and integer information available for the CTL_HW level 216is detailed below. 217The changeable column shows whether a process with appropriate 218privilege may change the value. 219.Bl -column "Second level nameXXXXXX" integerXXX -offset indent 220.It Sy Pa Second level name Type Changeable 221.It HW\_MACHINE string no 222.It HW\_MODEL string no 223.It HW\_NCPU integer no 224.It HW\_BYTEORDER integer no 225.It HW\_PHYSMEM integer no 226.It HW\_USERMEM integer no 227.It HW\_PAGESIZE integer no 228.It HW\_FLOATINGPOINT integer no 229.It HW\_MACHINE\_ARCH string no 230.\".It HW\_DISKNAMES integer no 231.\".It HW\_DISKSTATS integer no 232.El 233.Pp 234.Bl -tag -width "123456" 235.It Li HW_MACHINE 236The machine class. 237.It Li HW_MODEL 238The machine model 239.It Li HW_NCPU 240The number of cpus. 241.ne 1i 242.It Li HW_BYTEORDER 243The byteorder (4,321, or 1,234). 244.It Li HW_PHYSMEM 245The bytes of physical memory. 246.It Li HW_USERMEM 247The bytes of non-kernel memory. 248.It Li HW_PAGESIZE 249The software page size. 250.It Li HW_FLOATINGPOINT 251Nonzero if the floating point support is in hardware. 252.It Li HW_MACHINE_ARCH 253The machine dependent architecture type. 254.\".It Fa HW_DISKNAMES 255.\".It Fa HW_DISKSTATS 256.El 257.Ss CTL_KERN 258The string and integer information available for the CTL_KERN level 259is detailed below. 260The changeable column shows whether a process with appropriate 261privilege may change the value. 262The types of data currently available are process information, 263system vnodes, the open file entries, routing table entries, 264virtual memory statistics, load average history, and clock rate 265information. 266.Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent 267.It Sy Pa Second level name Type Changeable 268.It KERN\_ARGMAX integer no 269.It KERN\_BOOTFILE string yes 270.It KERN\_BOOTTIME struct timeval no 271.It KERN\_CLOCKRATE struct clockinfo no 272.It KERN\_FILE struct file no 273.It KERN\_HOSTID integer yes 274.It KERN\_HOSTNAME string yes 275.It KERN\_JOB\_CONTROL integer no 276.It KERN\_MAXFILES integer yes 277.It KERN\_MAXFILESPERPROC integer yes 278.It KERN\_MAXPROC integer no 279.It KERN\_MAXPROCPERUID integer yes 280.It KERN\_MAXVNODES integer yes 281.It KERN\_NGROUPS integer no 282.It KERN\_NISDOMAINNAME string yes 283.It KERN\_OSRELDATE integer no 284.It KERN\_OSRELEASE string no 285.It KERN\_OSREV integer no 286.It KERN\_OSTYPE string no 287.It KERN\_POSIX1 integer no 288.It KERN\_PROC struct proc no 289.It KERN\_PROF node not applicable 290.It KERN\_QUANTUM integer yes 291.It KERN\_SAVED\_IDS integer no 292.It KERN\_SECURELVL integer raise only 293.It KERN\_UPDATEINTERVAL integer no 294.It KERN\_VERSION string no 295.It KERN\_VNODE struct vnode no 296.El 297.ne 1i 298.Pp 299.Bl -tag -width "123456" 300.It Li KERN_ARGMAX 301The maximum bytes of argument to 302.Xr execve 2 . 303.It Li KERN_BOOTFILE 304The full pathname of the file from which the kernel was loaded. 305.It Li KERN_BOOTTIME 306A 307.Va struct timeval 308structure is returned. 309This structure contains the time that the system was booted. 310.It Li KERN_CLOCKRATE 311A 312.Va struct clockinfo 313structure is returned. 314This structure contains the clock, statistics clock and profiling clock 315frequencies, the number of micro-seconds per hz tick and the skew rate. 316.It Li KERN_FILE 317Return the entire file table. 318The returned data consists of a single 319.Va struct filehead 320followed by an array of 321.Va struct file , 322whose size depends on the current number of such objects in the system. 323.It Li KERN_HOSTID 324Get or set the host id. 325.It Li KERN_HOSTNAME 326Get or set the hostname. 327.It Li KERN_JOB_CONTROL 328Return 1 if job control is available on this system, otherwise 0. 329.It Li KERN_MAXFILES 330The maximum number of files that may be open in the system. 331.It Li KERN_MAXFILESPERPROC 332The maximum number of files that may be open for a single process. 333This limit only applies to processes with an effective uid of nonzero 334at the time of the open request. 335Files that have already been opened are not affected if the limit 336or the effective uid is changed. 337.It Li KERN_MAXPROC 338The maximum number of concurrent processes the system will allow. 339.It Li KERN_MAXPROCPERUID 340The maximum number of concurrent processes the system will allow 341for a single effective uid. 342This limit only applies to processes with an effective uid of nonzero 343at the time of a fork request. 344Processes that have already been started are not affected if the limit 345is changed. 346.It Li KERN_MAXVNODES 347The maximum number of vnodes available on the system. 348.It Li KERN_NGROUPS 349The maximum number of supplemental groups. 350.It Li KERN_NISDOMAINNAME 351The name of the current YP/NIS domain. 352.It Li KERN_OSRELDATE 353The system release date in YYYYMM format 354(January 1996 is encoded as 199601). 355.It Li KERN_OSRELEASE 356The system release string. 357.It Li KERN_OSREV 358The system revision string. 359.It Li KERN_OSTYPE 360The system type string. 361.It Li KERN_POSIX1 362The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 363attempts to comply. 364.It Li KERN_PROC 365Return the entire process table, or a subset of it. 366An array of 367.Va struct kinfo_proc 368structures is returned, 369whose size depends on the current number of such objects in the system. 370The third and fourth level names are as follows: 371.Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent 372.It Pa Third level name Fourth level is: 373.It KERN\_PROC\_ALL None 374.It KERN\_PROC\_PID A process ID 375.It KERN\_PROC\_PGRP A process group 376.It KERN\_PROC\_TTY A tty device 377.It KERN\_PROC\_UID A user ID 378.It KERN\_PROC\_RUID A real user ID 379.El 380.It Li KERN_PROF 381Return profiling information about the kernel. 382If the kernel is not compiled for profiling, 383attempts to retrieve any of the KERN_PROF values will 384fail with EOPNOTSUPP. 385The third level names for the string and integer profiling information 386is detailed below. 387The changeable column shows whether a process with appropriate 388privilege may change the value. 389.Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent 390.It Sy Pa Third level name Type Changeable 391.It GPROF\_STATE integer yes 392.It GPROF\_COUNT u_short[\|] yes 393.It GPROF\_FROMS u_short[\|] yes 394.It GPROF\_TOS struct tostruct yes 395.It GPROF\_GMONPARAM struct gmonparam no 396.El 397.Pp 398The variables are as follows: 399.Bl -tag -width "123456" 400.It Li GPROF_STATE 401Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling 402is running or stopped. 403.It Li GPROF_COUNT 404Array of statistical program counter counts. 405.It Li GPROF_FROMS 406Array indexed by program counter of call-from points. 407.It Li GPROF_TOS 408Array of 409.Va struct tostruct 410describing destination of calls and their counts. 411.It Li GPROF_GMONPARAM 412Structure giving the sizes of the above arrays. 413.El 414.ne 1i 415.It Li KERN_QUANTUM 416The maximum period of time, in microseconds, for which a process is allowed 417to run without being preempted if other processes are in the run queue. 418.It Li KERN_SAVED_IDS 419Returns 1 if saved set-group and saved set-user ID is available. 420.It Li KERN_SECURELVL 421The system security level. 422This level may be raised by processes with appropriate privilege. 423It may not be lowered. 424.It Li KERN_VERSION 425The system version string. 426.It Li KERN_VNODE 427Return the entire vnode table. 428Note, the vnode table is not necessarily a consistent snapshot of 429the system. 430The returned data consists of an array whose size depends on the 431current number of such objects in the system. 432Each element of the array contains the kernel address of a vnode 433.Va struct vnode * 434followed by the vnode itself 435.Va struct vnode . 436.El 437.Ss CTL_MACHDEP 438The set of variables defined is architecture dependent. 439The following variables are defined for the i386 architecture. 440.Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent 441.It Sy Pa Second level name Type Changeable 442.It Li CPU_CONSDEV dev_t no 443.It Li CPU_ADJKERNTZ int yes 444.It Li CPU_DISRTCSET int yes 445.It Li CPU_BOOTINFO struct bootinfo no 446.It Li CPU_WALLCLOCK int yes 447.El 448.Ss CTL_NET 449The string and integer information available for the CTL_NET level 450is detailed below. 451The changeable column shows whether a process with appropriate 452privilege may change the value. 453.Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent 454.It Sy Pa Second level name Type Changeable 455.It PF\_ROUTE routing messages no 456.It PF\_INET IPv4 values yes 457.It PF\_INET6 IPv6 values yes 458.El 459.Pp 460.Bl -tag -width "123456" 461.It Li PF_ROUTE 462Return the entire routing table or a subset of it. 463The data is returned as a sequence of routing messages (see 464.Xr route 4 465for the header file, format and meaning). 466The length of each message is contained in the message header. 467.Pp 468The third level name is a protocol number, which is currently always 0. 469The fourth level name is an address family, which may be set to 0 to 470select all address families. 471The fifth and sixth level names are as follows: 472.Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent 473.It Pa Fifth level name Sixth level is: 474.It NET\_RT\_FLAGS rtflags 475.It NET\_RT\_DUMP None 476.It NET\_RT\_IFLIST None 477.El 478.It Li PF_INET 479Get or set various global information about the IPv4 480.Pq Internet Protocol version 4 . 481The third level name is the protocol. 482The fourth level name is the variable name. 483The currently defined protocols and names are: 484.ne 1i 485.Bl -column ProtocolXX VariableXX TypeXX ChangeableXX 486.It Pa Protocol Variable Type Changeable 487.It icmp bmcastecho integer yes 488.It icmp maskrepl integer yes 489.It ip forwarding integer yes 490.It ip redirect integer yes 491.It ip ttl integer yes 492.It udp checksum integer yes 493.El 494.Pp 495The variables are as follows: 496.Bl -tag -width "123456" 497.It Li icmp.bmcastecho 498Returns 1 if an ICMP echo request to a broadcast or multicast address is 499to be answered. 500.It Li icmp.maskrepl 501Returns 1 if ICMP network mask requests are to be answered. 502.It Li ip.forwarding 503Returns 1 when IP forwarding is enabled for the host, 504meaning that the host is acting as a router. 505.It Li ip.redirect 506Returns 1 when ICMP redirects may be sent by the host. 507This option is ignored unless the host is routing IP packets, 508and should normally be enabled on all systems. 509.It Li ip.ttl 510The maximum time-to-live (hop count) value for an IP packet sourced by 511the system. 512This value applies to normal transport protocols, not to ICMP. 513.It Li udp.checksum 514Returns 1 when UDP checksums are being computed and checked. 515Disabling UDP checksums is strongly discouraged. 516.Pp 517For variables net.inet.*.ipsec, please refer to 518.Xr ipsec 4 . 519.El 520.It Li PF_INET6 521Get or set various global information about the IPv6 522.Pq Internet Protocol version 6 . 523The third level name is the protocol. 524The fourth level name is the variable name. 525.Pp 526For variables net.inet6.* please refer to 527.Xr inet6 4 . 528For variables net.inet6.*.ipsec6, please refer to 529.Xr ipsec 4 . 530.El 531.Ss CTL_USER 532The string and integer information available for the CTL_USER level 533is detailed below. 534The changeable column shows whether a process with appropriate 535privilege may change the value. 536.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent 537.It Sy Pa Second level name Type Changeable 538.It USER\_BC\_BASE\_MAX integer no 539.It USER\_BC\_DIM\_MAX integer no 540.It USER\_BC\_SCALE\_MAX integer no 541.It USER\_BC\_STRING\_MAX integer no 542.It USER\_COLL\_WEIGHTS\_MAX integer no 543.It USER\_CS\_PATH string no 544.It USER\_EXPR\_NEST\_MAX integer no 545.It USER\_LINE\_MAX integer no 546.It USER\_POSIX2\_CHAR\_TERM integer no 547.It USER\_POSIX2\_C\_BIND integer no 548.It USER\_POSIX2\_C\_DEV integer no 549.It USER\_POSIX2\_FORT\_DEV integer no 550.It USER\_POSIX2\_FORT\_RUN integer no 551.It USER\_POSIX2\_LOCALEDEF integer no 552.It USER\_POSIX2\_SW\_DEV integer no 553.It USER\_POSIX2\_UPE integer no 554.It USER\_POSIX2\_VERSION integer no 555.It USER\_RE\_DUP\_MAX integer no 556.It USER\_STREAM\_MAX integer no 557.It USER\_TZNAME\_MAX integer no 558.El 559.Bl -tag -width "123456" 560.Pp 561.It Li USER_BC_BASE_MAX 562The maximum ibase/obase values in the 563.Xr bc 1 564utility. 565.It Li USER_BC_DIM_MAX 566The maximum array size in the 567.Xr bc 1 568utility. 569.It Li USER_BC_SCALE_MAX 570The maximum scale value in the 571.Xr bc 1 572utility. 573.It Li USER_BC_STRING_MAX 574The maximum string length in the 575.Xr bc 1 576utility. 577.It Li USER_COLL_WEIGHTS_MAX 578The maximum number of weights that can be assigned to any entry of 579the LC_COLLATE order keyword in the locale definition file. 580.It Li USER_CS_PATH 581Return a value for the 582.Ev PATH 583environment variable that finds all the standard utilities. 584.It Li USER_EXPR_NEST_MAX 585The maximum number of expressions that can be nested within 586parenthesis by the 587.Xr expr 1 588utility. 589.It Li USER_LINE_MAX 590The maximum length in bytes of a text-processing utility's input 591line. 592.It Li USER_POSIX2_CHAR_TERM 593Return 1 if the system supports at least one terminal type capable of 594all operations described in POSIX 1003.2, otherwise 0. 595.It Li USER_POSIX2_C_BIND 596Return 1 if the system's C-language development facilities support the 597C-Language Bindings Option, otherwise 0. 598.It Li USER_POSIX2_C_DEV 599Return 1 if the system supports the C-Language Development Utilities Option, 600otherwise 0. 601.It Li USER_POSIX2_FORT_DEV 602Return 1 if the system supports the FORTRAN Development Utilities Option, 603otherwise 0. 604.It Li USER_POSIX2_FORT_RUN 605Return 1 if the system supports the FORTRAN Runtime Utilities Option, 606otherwise 0. 607.It Li USER_POSIX2_LOCALEDEF 608Return 1 if the system supports the creation of locales, otherwise 0. 609.It Li USER_POSIX2_SW_DEV 610Return 1 if the system supports the Software Development Utilities Option, 611otherwise 0. 612.It Li USER_POSIX2_UPE 613Return 1 if the system supports the User Portability Utilities Option, 614otherwise 0. 615.It Li USER_POSIX2_VERSION 616The version of POSIX 1003.2 with which the system attempts to comply. 617.It Li USER_RE_DUP_MAX 618The maximum number of repeated occurrences of a regular expression 619permitted when using interval notation. 620.ne 1i 621.It Li USER_STREAM_MAX 622The minimum maximum number of streams that a process may have open 623at any one time. 624.It Li USER_TZNAME_MAX 625The minimum maximum number of types supported for the name of a 626timezone. 627.El 628.Ss CTL_VM 629The string and integer information available for the CTL_VM level 630is detailed below. 631The changeable column shows whether a process with appropriate 632privilege may change the value. 633.Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent 634.It Sy Pa Second level name Type Changeable 635.It VM\_LOADAVG struct loadavg no 636.It VM\_METER struct vmtotal no 637.It VM\_PAGEOUT\_ALGORITHM integer yes 638.It VM\_SWAPPING\_ENABLED integer maybe 639.It VM\_V\_CACHE\_MAX integer yes 640.It VM\_V\_CACHE\_MIN integer yes 641.It VM\_V\_FREE\_MIN integer yes 642.It VM\_V\_FREE\_RESERVED integer yes 643.It VM\_V\_FREE\_TARGET integer yes 644.It VM\_V\_INACTIVE\_TARGET integer yes 645.It VM\_V\_PAGEOUT\_FREE\_MIN integer yes 646.El 647.Pp 648.Bl -tag -width "123456" 649.It Li VM_LOADAVG 650Return the load average history. 651The returned data consists of a 652.Va struct loadavg . 653.It Li VM_METER 654Return the system wide virtual memory statistics. 655The returned data consists of a 656.Va struct vmtotal . 657.It Li VM_PAGEOUT_ALGORITHM 6580 if the statistics-based page management algorithm is in use 659or 1 if the near-LRU algorithm is in use. 660.It Li VM_SWAPPING_ENABLED 6611 if process swapping is enabled or 0 if disabled. This variable is 662permanently set to 0 if the kernel was built with swapping disabled. 663.It Li VM_V_CACHE_MAX 664Maximum desired size of the cache queue. 665.It Li VM_V_CACHE_MIN 666Minimum desired size of the cache queue. If the cache queue size 667falls very far below this value, the pageout daemon is awakened. 668.It Li VM_V_FREE_MIN 669Minimum amount of memory (cache memory plus free memory) 670required to be available before a process waiting on memory will be 671awakened. 672.It Li VM_V_FREE_RESERVED 673Processes will awaken the pageout daemon and wait for memory if the 674number of free and cached pages drops below this value. 675.It Li VM_V_FREE_TARGET 676The total amount of free memory (including cache memory) that the 677pageout daemon tries to maintain. 678.It Li VM_V_INACTIVE_TARGET 679The desired number of inactive pages that the pageout daemon should 680achieve when it runs. Inactive pages can be quickly inserted into 681process address space when needed. 682.It Li VM_V_PAGEOUT_FREE_MIN 683If the amount of free and cache memory falls below this value, the 684pageout daemon will enter "memory conserving mode" to avoid deadlock. 685.El 686.Sh RETURN VALUES 687.Fn sysctl 688and 689.Fn sysctlbyname 690return 0 when successful. 691Otherwise \-1 is returned and 692.Va errno 693is set appropriately. 694.Sh ERRORS 695The following errors may be reported: 696.Bl -tag -width Er 697.It Bq Er EFAULT 698The buffer 699.Fa name , 700.Fa oldp , 701.Fa newp , 702or length pointer 703.Fa oldlenp 704contains an invalid address. 705.It Bq Er EINVAL 706The 707.Fa name 708array is less than two or greater than CTL_MAXNAME. 709.It Bq Er EINVAL 710A non-null 711.Fa newp 712is given and its specified length in 713.Fa newlen 714is too large or too small. 715.It Bq Er ENOMEM 716The length pointed to by 717.Fa oldlenp 718is too short to hold the requested value. 719.It Bq Er ENOTDIR 720The 721.Fa name 722array specifies an intermediate rather than terminal name. 723.It Bq Er EISDIR 724The 725.Fa name 726array specifies a terminal name, but the actual name is not terminal. 727.It Bq Er EOPNOTSUPP 728The 729.Fa name 730array specifies a value that is unknown. 731.It Bq Er EPERM 732An attempt is made to set a read-only value. 733.It Bq Er EPERM 734A process without appropriate privilege attempts to set a value. 735.El 736.Sh FILES 737.Bl -tag -width <netinet/icmpXvar.h> -compact 738.It Aq Pa sys/sysctl.h 739definitions for top level identifiers, second level kernel and hardware 740identifiers, and user level identifiers 741.It Aq Pa sys/socket.h 742definitions for second level network identifiers 743.It Aq Pa sys/gmon.h 744definitions for third level profiling identifiers 745.It Aq Pa vm/vm_param.h 746definitions for second level virtual memory identifiers 747.It Aq Pa netinet/in.h 748definitions for third level IPv4/IPv6 identifiers and 749fourth level IPv4/v6 identifiers 750.It Aq Pa netinet/icmp_var.h 751definitions for fourth level ICMP identifiers 752.It Aq Pa netinet/icmp6.h 753definitions for fourth level ICMPv6 identifiers 754.It Aq Pa netinet/udp_var.h 755definitions for fourth level UDP identifiers 756.El 757.Sh SEE ALSO 758.Xr sysconf 3 , 759.Xr sysctl 8 760.Sh HISTORY 761The 762.Fn sysctl 763function first appeared in 764.Bx 4.4 . 765