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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 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 $ 30.\" 31.Dd November 24, 2013 32.Dt SYSCTL 3 33.Os 34.Sh NAME 35.Nm sysctl , 36.Nm sysctlbyname , 37.Nm sysctlnametomib 38.Nd get or set system information 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In sys/types.h 43.In sys/sysctl.h 44.Ft int 45.Fn sysctl "const int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen" 46.Ft int 47.Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen" 48.Ft int 49.Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep" 50.Sh DESCRIPTION 51The 52.Fn sysctl 53function retrieves system information and allows processes with 54appropriate privileges to set system information. 55The information available from 56.Fn sysctl 57consists of integers, strings, and tables. 58Information may be retrieved and set from the command interface 59using the 60.Xr sysctl 8 61utility. 62.Pp 63Unless explicitly noted below, 64.Fn sysctl 65returns a consistent snapshot of the data requested. 66Consistency is obtained by locking the destination 67buffer into memory so that the data may be copied out without blocking. 68Calls to 69.Fn sysctl 70are serialized to avoid deadlock. 71.Pp 72The state is described using a ``Management Information Base'' (MIB) 73style name, listed in 74.Fa name , 75which is a 76.Fa namelen 77length array of integers. 78.Pp 79The 80.Fn sysctlbyname 81function accepts an ASCII representation of the name and internally 82looks up the integer name vector. Apart from that, it behaves the same 83as the standard 84.Fn sysctl 85function. 86.Pp 87The information is copied into the buffer specified by 88.Fa oldp . 89The size of the buffer is given by the location specified by 90.Fa oldlenp 91before the call, 92and that location gives the amount of data copied after a successful call 93and after a call that returns with the error code 94.Er 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 99.Er ENOMEM . 100If the old value is not desired, 101.Fa oldp 102and 103.Fa oldlenp 104should be set to NULL. 105.Pp 106The size of the available data can be determined by calling 107.Fn sysctl 108with a NULL parameter for 109.Fa oldp . 110The size of the available data will be returned in the location pointed to by 111.Fa oldlenp . 112For some operations, the amount of space may change often. 113For these operations, 114the system attempts to round up so that the returned size is 115large enough for a call to return the data shortly thereafter. 116.Pp 117To set a new value, 118.Fa newp 119is set to point to a buffer of length 120.Fa newlen 121from which the requested value is to be taken. 122If a new value is not to be set, 123.Fa newp 124should be set to NULL and 125.Fa newlen 126set to 0. 127.Pp 128The 129.Fn sysctlnametomib 130function accepts an ASCII representation of the name, 131looks up the integer name vector, 132and returns the numeric representation in the mib array pointed to by 133.Fa mibp . 134The number of elements in the mib array is given by the location specified by 135.Fa sizep 136before the call, 137and that location gives the number of entries copied after a successful call. 138The resulting 139.Fa mib 140and 141.Fa size 142may be used in subsequent 143.Fn sysctl 144calls to get the data associated with the requested ASCII name. 145This interface is intended for use by applications that want to 146repeatedly request the same variable (the 147.Fn sysctl 148function runs in about a third the time as the same request made via the 149.Fn sysctlbyname 150function). 151The 152.Fn sysctlnametomib 153function is also useful for fetching mib prefixes and then adding 154a final component. 155For example, to fetch process information 156for processes with pid's less than 100: 157.Pp 158.Bd -literal -offset indent -compact 159int i, mib[4]; 160size_t len; 161struct kinfo_proc kp; 162 163/* Fill out the first three components of the mib */ 164len = 4; 165sysctlnametomib("kern.proc.pid", mib, &len); 166 167/* Fetch and print entries for pid's < 100 */ 168for (i = 0; i < 100; i++) { 169 mib[3] = i; 170 len = sizeof(kp); 171 if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1) 172 perror("sysctl"); 173 else if (len > 0) 174 printkproc(&kp); 175} 176.Ed 177.Pp 178The top level names are defined with a CTL_ prefix in 179.In sys/sysctl.h , 180and are as follows. 181The next and subsequent levels down are found in the include files 182listed 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" 193.El 194.Pp 195For example, the following retrieves the maximum number of processes allowed 196in the system: 197.Pp 198.Bd -literal -offset indent -compact 199int mib[2], maxproc; 200size_t len; 201 202mib[0] = CTL_KERN; 203mib[1] = KERN_MAXPROC; 204len = sizeof(maxproc); 205sysctl(mib, 2, &maxproc, &len, NULL, 0); 206.Ed 207.Pp 208To retrieve the standard search path for the system utilities: 209.Pp 210.Bd -literal -offset indent -compact 211int mib[2]; 212size_t len; 213char *p; 214 215mib[0] = CTL_USER; 216mib[1] = USER_CS_PATH; 217sysctl(mib, 2, NULL, &len, NULL, 0); 218p = malloc(len); 219sysctl(mib, 2, p, &len, NULL, 0); 220.Ed 221.Ss CTL_DEBUG 222The debugging variables vary from system to system. 223A debugging variable may be added or deleted without need to recompile 224.Fn sysctl 225to know about it. 226Each time it runs, 227.Fn sysctl 228gets the list of debugging variables from the kernel and 229displays their current values. 230The system defines twenty 231.Ns ( Va struct ctldebug ) 232variables named 233.Nm debug0 234through 235.Nm debug19 . 236They are declared as separate variables so that they can be 237individually initialized at the location of their associated variable. 238The loader prevents multiple use of the same variable by issuing errors 239if a variable is initialized in more than one place. 240For example, to export the variable 241.Nm dospecialcheck 242as a debugging variable, the following declaration would be used: 243.Bd -literal -offset indent -compact 244int dospecialcheck = 1; 245struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; 246.Ed 247.Ss CTL_VFS 248A distinguished second level name, VFS_GENERIC, 249is used to get general information about all filesystems. 250One of its third level identifiers is VFS_MAXTYPENUM 251that gives the highest valid filesystem type number. 252Its other third level identifier is VFS_CONF that 253returns configuration information about the filesystem 254type given as a fourth level identifier (see 255.Xr getvfsbyname 3 256as an example of its use). 257The remaining second level identifiers are the 258filesystem type number returned by a 259.Xr statfs 2 260call or from VFS_CONF. 261The third level identifiers available for each filesystem 262are given in the header file that defines the mount 263argument structure for that filesystem. 264.Ss CTL_HW 265The string and integer information available for the CTL_HW level 266is detailed below. 267The changeable column shows whether a process with appropriate 268privilege 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" 283.El 284.Bl -tag -width 6n 285.It Li HW_MACHINE 286The machine class. 287.It Li HW_MODEL 288The machine model 289.It Li HW_NCPU 290The number of cpus. 291.It Li HW_BYTEORDER 292The byteorder (4,321, or 1,234). 293.It Li HW_PHYSMEM 294The bytes of physical memory. 295.It Li HW_USERMEM 296The bytes of non-kernel memory. 297.It Li HW_PAGESIZE 298The software page size. 299.It Li HW_FLOATINGPOINT 300Nonzero if the floating point support is in hardware. 301.It Li HW_MACHINE_ARCH 302The machine dependent architecture type. 303.\".It Fa HW_DISKNAMES 304.\".It Fa HW_DISKSTATS 305.It Li HW_SENSORS 306Third level comprises an array of 307.Vt "struct sensordev" 308structures containing information about devices 309that may attach hardware monitoring sensors. 310.Pp 311Third, fourth and fifth levels together comprise an array of 312.Vt "struct sensor" 313structures containing snapshot readings of hardware monitoring sensors. 314In such usage, third level indicates the numerical representation 315of the sensor device name to which the sensor is attached 316(device's 317.Va xname 318and number shall be matched with the help of 319.Vt "struct sensordev" 320structure above), 321fourth level indicates sensor type and 322fifth level is an ordinal sensor number (unique to 323the specified sensor type on the specified sensor device). 324.Pp 325The 326.Vt sensordev 327and 328.Vt sensor 329structures 330and 331.Vt sensor_type 332enumeration 333are defined in 334.In sys/sensors.h . 335.El 336.Ss CTL_KERN 337The string and integer information available for the CTL_KERN level 338is detailed below. 339The changeable column shows whether a process with appropriate 340privilege may change the value. 341The types of data currently available are process information, 342system vnodes, the open file entries, routing table entries, 343virtual memory statistics, load average history, and clock rate 344information. 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" 376.El 377.Bl -tag -width 6n 378.It Li KERN_ARGMAX 379The maximum bytes of argument to 380.Xr execve 2 . 381.It Li KERN_BOOTFILE 382The full pathname of the file from which the kernel was loaded. 383.It Li KERN_BOOTTIME 384A 385.Va struct timeval 386structure is returned. 387This structure contains the time that the system was booted. 388.It Li KERN_CLOCKRATE 389A 390.Va struct clockinfo 391structure is returned. 392This structure contains the clock, statistics clock and profiling clock 393frequencies, the number of micro-seconds per hz tick and the skew rate. 394.It Li KERN_FILE 395Return the entire file table. 396The returned data consists of a single 397.Va struct filehead 398followed by an array of 399.Va struct file , 400whose size depends on the current number of such objects in the system. 401.It Li KERN_HOSTID 402Get or set the host id. 403.It Li KERN_HOSTNAME 404Get or set the hostname. 405.It Li KERN_JOB_CONTROL 406Return 1 if job control is available on this system, otherwise 0. 407.It Li KERN_MAXFILES 408The maximum number of files that may be open in the system. 409.It Li KERN_MAXFILESPERPROC 410The maximum number of files that may be open for a single process. 411This limit only applies to processes with an effective uid of nonzero 412at the time of the open request. 413Files that have already been opened are not affected if the limit 414or the effective uid is changed. 415.It Li KERN_MAXPROC 416The maximum number of concurrent processes the system will allow. 417.It Li KERN_MAXPROCPERUID 418The maximum number of concurrent processes the system will allow 419for a single effective uid. 420This limit only applies to processes with an effective uid of nonzero 421at the time of a fork request. 422Processes that have already been started are not affected if the limit 423is changed. 424.It Li KERN_MAXVNODES 425The maximum number of vnodes available on the system. 426.It Li KERN_NGROUPS 427The maximum number of supplemental groups. 428.It Li KERN_NISDOMAINNAME 429The name of the current YP/NIS domain. 430.It Li KERN_OSRELDATE 431The system release date in YYYYMM format 432(January 1996 is encoded as 199601). 433.It Li KERN_OSRELEASE 434The system release string. 435.It Li KERN_OSREV 436The system revision string. 437.It Li KERN_OSTYPE 438The system type string. 439.It Li KERN_POSIX1 440The version of 441.St -p1003.1 442with which the system 443attempts to comply. 444.It Li KERN_PROC 445Return the entire process table, or a subset of it. 446An array of 447.Va struct kinfo_proc 448structures is returned, 449whose size depends on the current number of such objects in the system. 450The 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" 459.El 460.Pp 461Adding the flag 462.Li KERN_PROC_FLAG_LWP 463to the third level name signals that information about all 464light weight processes of the selected processes should be returned. 465.It Li KERN_PROF 466Return profiling information about the kernel. 467If the kernel is not compiled for profiling, 468attempts to retrieve any of the KERN_PROF values will 469fail with 470.Er ENOENT . 471The third level names for the string and integer profiling information 472is detailed below. 473The changeable column shows whether a process with appropriate 474privilege 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" 482.El 483.Pp 484The variables are as follows: 485.Bl -tag -width 6n 486.It Li GPROF_STATE 487Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling 488is running or stopped. 489.It Li GPROF_COUNT 490Array of statistical program counter counts. 491.It Li GPROF_FROMS 492Array indexed by program counter of call-from points. 493.It Li GPROF_TOS 494Array of 495.Va struct tostruct 496describing destination of calls and their counts. 497.It Li GPROF_GMONPARAM 498Structure giving the sizes of the above arrays. 499.El 500.It Li KERN_QUANTUM 501The maximum period of time, in microseconds, for which a process is allowed 502to run without being preempted if other processes are in the run queue. 503.It Li KERN_SAVED_IDS 504Returns 1 if saved set-group and saved set-user ID is available. 505.It Li KERN_SECURELVL 506The system security level. 507This level may be raised by processes with appropriate privilege. 508It may not be lowered. 509.It Li KERN_VERSION 510The system version string. 511.It Li KERN_VNODE 512Return the entire vnode table. 513Note, the vnode table is not necessarily a consistent snapshot of 514the system. 515The returned data consists of an array whose size depends on the 516current number of such objects in the system. 517Each element of the array contains the kernel address of a vnode 518.Va struct vnode * 519followed by the vnode itself 520.Va struct vnode . 521.El 522.Ss CTL_MACHDEP 523The set of variables defined is architecture dependent. 524The 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" 532.El 533.Ss CTL_NET 534The string and integer information available for the CTL_NET level 535is detailed below. 536The changeable column shows whether a process with appropriate 537privilege 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" 543.El 544.Bl -tag -width 6n 545.It Li PF_ROUTE 546Return the entire routing table or a subset of it. 547The data is returned as a sequence of routing messages (see 548.Xr route 4 549for the header file, format and meaning). 550The length of each message is contained in the message header. 551.Pp 552The third level name is a protocol number, which is currently always 0. 553The fourth level name is an address family, which may be set to 0 to 554select all address families. 555The 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" 561.El 562.It Li PF_INET 563Get or set various global information about the IPv4 564(Internet Protocol version 4). 565The third level name is the protocol. 566The fourth level name is the variable name. 567The 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" 576.El 577.Pp 578The variables are as follows: 579.Bl -tag -width 6n 580.It Li icmp.bmcastecho 581Returns 1 if an ICMP echo request to a broadcast or multicast address is 582to be answered. 583.It Li icmp.maskrepl 584Returns 1 if ICMP network mask requests are to be answered. 585.It Li ip.forwarding 586Returns 1 when IP forwarding is enabled for the host, 587meaning that the host is acting as a router. 588.It Li ip.redirect 589Returns 1 when ICMP redirects may be sent by the host. 590This option is ignored unless the host is routing IP packets, 591and should normally be enabled on all systems. 592.It Li ip.ttl 593The maximum time-to-live (hop count) value for an IP packet sourced by 594the system. 595This value applies to normal transport protocols, not to ICMP. 596.It Li udp.checksum 597Returns 1 when UDP checksums are being computed and checked. 598Disabling UDP checksums is strongly discouraged. 599.Pp 600For variables net.inet.*.ipsec, please refer to 601.Xr ipsec 4 . 602.El 603.It Li PF_INET6 604Get or set various global information about the IPv6 605(Internet Protocol version 6). 606The third level name is the protocol. 607The fourth level name is the variable name. 608.Pp 609For variables net.inet6.* please refer to 610.Xr inet6 4 . 611For variables net.inet6.*.ipsec6, please refer to 612.Xr ipsec 4 . 613.El 614.Ss CTL_USER 615The string and integer information available for the CTL_USER level 616is detailed below. 617The changeable column shows whether a process with appropriate 618privilege 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" 641.El 642.Bl -tag -width 6n 643.It Li USER_BC_BASE_MAX 644The maximum ibase/obase values in the 645.Xr bc 1 646utility. 647.It Li USER_BC_DIM_MAX 648The maximum array size in the 649.Xr bc 1 650utility. 651.It Li USER_BC_SCALE_MAX 652The maximum scale value in the 653.Xr bc 1 654utility. 655.It Li USER_BC_STRING_MAX 656The maximum string length in the 657.Xr bc 1 658utility. 659.It Li USER_COLL_WEIGHTS_MAX 660The maximum number of weights that can be assigned to any entry of 661the LC_COLLATE order keyword in the locale definition file. 662.It Li USER_CS_PATH 663Return a value for the 664.Ev PATH 665environment variable that finds all the standard utilities. 666.It Li USER_EXPR_NEST_MAX 667The maximum number of expressions that can be nested within 668parenthesis by the 669.Xr expr 1 670utility. 671.It Li USER_LINE_MAX 672The maximum length in bytes of a text-processing utility's input 673line. 674.It Li USER_POSIX2_CHAR_TERM 675Return 1 if the system supports at least one terminal type capable of 676all operations described in 677.St -p1003.2 , 678otherwise 0. 679.It Li USER_POSIX2_C_BIND 680Return 1 if the system's C-language development facilities support the 681C-Language Bindings Option, otherwise 0. 682.It Li USER_POSIX2_C_DEV 683Return 1 if the system supports the C-Language Development Utilities Option, 684otherwise 0. 685.It Li USER_POSIX2_FORT_DEV 686Return 1 if the system supports the FORTRAN Development Utilities Option, 687otherwise 0. 688.It Li USER_POSIX2_FORT_RUN 689Return 1 if the system supports the FORTRAN Runtime Utilities Option, 690otherwise 0. 691.It Li USER_POSIX2_LOCALEDEF 692Return 1 if the system supports the creation of locales, otherwise 0. 693.It Li USER_POSIX2_SW_DEV 694Return 1 if the system supports the Software Development Utilities Option, 695otherwise 0. 696.It Li USER_POSIX2_UPE 697Return 1 if the system supports the User Portability Utilities Option, 698otherwise 0. 699.It Li USER_POSIX2_VERSION 700The version of 701.St -p1003.2 702with which the system attempts to comply. 703.It Li USER_RE_DUP_MAX 704The maximum number of repeated occurrences of a regular expression 705permitted when using interval notation. 706.It Li USER_STREAM_MAX 707The minimum maximum number of streams that a process may have open 708at any one time. 709.It Li USER_TZNAME_MAX 710The minimum maximum number of types supported for the name of a 711timezone. 712.El 713.Ss CTL_VM 714The string and integer information available for the CTL_VM level 715is detailed below. 716The changeable column shows whether a process with appropriate 717privilege 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" 731.El 732.Bl -tag -width 6n 733.It Li VM_LOADAVG 734Return the load average history. 735The returned data consists of a 736.Va struct loadavg . 737.It Li VM_METER 738Return the system wide virtual memory statistics. 739The returned data consists of a 740.Va struct vmtotal . 741.It Li VM_PAGEOUT_ALGORITHM 7420 if the statistics-based page management algorithm is in use 743or 1 if the near-LRU algorithm is in use. 744.It Li VM_SWAPPING_ENABLED 7451 if process swapping is enabled or 0 if disabled. This variable is 746permanently set to 0 if the kernel was built with swapping disabled. 747.It Li VM_V_CACHE_MAX 748Maximum desired size of the cache queue. 749.It Li VM_V_CACHE_MIN 750Minimum desired size of the cache queue. If the cache queue size 751falls very far below this value, the pageout daemon is awakened. 752.It Li VM_V_FREE_MIN 753Minimum amount of memory (cache memory plus free memory) 754required to be available before a process waiting on memory will be 755awakened. 756.It Li VM_V_FREE_RESERVED 757Processes will awaken the pageout daemon and wait for memory if the 758number of free and cached pages drops below this value. 759.It Li VM_V_FREE_TARGET 760The total amount of free memory (including cache memory) that the 761pageout daemon tries to maintain. 762.It Li VM_V_INACTIVE_TARGET 763The desired number of inactive pages that the pageout daemon should 764achieve when it runs. Inactive pages can be quickly inserted into 765process address space when needed. 766.It Li VM_V_PAGEOUT_FREE_MIN 767If the amount of free and cache memory falls below this value, the 768pageout daemon will enter "memory conserving mode" to avoid deadlock. 769.El 770.Sh RETURN VALUES 771.Rv -std 772.Sh FILES 773.Bl -tag -width ".In netinet/icmp_var.h" -compact 774.It In sys/sysctl.h 775definitions for top level identifiers, second level kernel and hardware 776identifiers, and user level identifiers 777.It In sys/socket.h 778definitions for second level network identifiers 779.It In sys/gmon.h 780definitions for third level profiling identifiers 781.It In vm/vm_param.h 782definitions for second level virtual memory identifiers 783.It In netinet/in.h 784definitions for third level IPv4/IPv6 identifiers and 785fourth level IPv4/v6 identifiers 786.It In netinet/icmp_var.h 787definitions for fourth level ICMP identifiers 788.It In netinet/icmp6.h 789definitions for fourth level ICMPv6 identifiers 790.It In netinet/udp_var.h 791definitions for fourth level UDP identifiers 792.El 793.Sh ERRORS 794The following errors may be reported: 795.Bl -tag -width Er 796.It Bq Er EFAULT 797The buffer 798.Fa name , 799.Fa oldp , 800.Fa newp , 801or length pointer 802.Fa oldlenp 803contains an invalid address. 804.It Bq Er EINVAL 805The 806.Fa name 807array is less than two or greater than CTL_MAXNAME. 808.It Bq Er EINVAL 809A non-null 810.Fa newp 811is given and its specified length in 812.Fa newlen 813is too large or too small. 814.It Bq Er ENOMEM 815The length pointed to by 816.Fa oldlenp 817is too short to hold the requested value. 818.It Bq Er ENOTDIR 819The 820.Fa name 821array specifies an intermediate rather than terminal name. 822.It Bq Er EISDIR 823The 824.Fa name 825array specifies a terminal name, but the actual name is not terminal. 826.It Bq Er ENOENT 827The 828.Fa name 829array specifies a value that is unknown. 830.It Bq Er EPERM 831An attempt is made to set a read-only value. 832.It Bq Er EPERM 833A process without appropriate privilege attempts to set a value. 834.El 835.Sh SEE ALSO 836.Xr sysconf 3 , 837.Xr sysctl 8 838.Sh HISTORY 839The 840.Fn sysctl 841function first appeared in 842.Bx 4.4 . 843