gen/sysctl.3

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  32 .\"     @(#)sysctl.3    8.4 (Berkeley) 5/9/95
  33 .\" $FreeBSD: src/lib/libc/gen/sysctl.3,v 1.51 2001/10/01 16:08:51 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.  Apart from that, it behaves the same
  87 as the standard
  88 .Fn sysctl
  89 function.
  90 .Pp
  91 The information is copied into the buffer specified by
  92 .Fa oldp .
  93 The size of the buffer is given by the location specified by
  94 .Fa oldlenp
  95 before the call,
  96 and that location gives the amount of data copied after a successful call
  97 and after a call that returns with the error code
  98 .Er ENOMEM .
  99 If the amount of data available is greater
 100 than the size of the buffer supplied,
 101 the call supplies as much data as fits in the buffer provided
 102 and returns with the error code
 103 .Er ENOMEM .
 104 If the old value is not desired,
 105 .Fa oldp
 106 and
 107 .Fa oldlenp
 108 should be set to NULL.
 109 .Pp
 110 The size of the available data can be determined by calling
 111 .Fn sysctl
 112 with a NULL parameter for
 113 .Fa oldp .
 114 The size of the available data will be returned in the location pointed to by
 115 .Fa oldlenp .
 116 For some operations, the amount of space may change often.
 117 For these operations,
 118 the system attempts to round up so that the returned size is
 119 large enough for a call to return the data shortly thereafter.
 120 .Pp
 121 To set a new value,
 122 .Fa newp
 123 is set to point to a buffer of length
 124 .Fa newlen
 125 from which the requested value is to be taken.
 126 If a new value is not to be set,
 127 .Fa newp
 128 should be set to NULL and
 129 .Fa newlen
 130 set to 0.
 131 .Pp
 132 The
 133 .Fn sysctlnametomib
 134 function accepts an ASCII representation of the name,
 135 looks up the integer name vector,
 136 and returns the numeric representation in the mib array pointed to by
 137 .Fa mibp .
 138 The number of elements in the mib array is given by the location specified by
 139 .Fa sizep
 140 before the call,
 141 and that location gives the number of entries copied after a successful call.
 142 The resulting
 143 .Fa mib
 144 and
 145 .Fa size
 146 may be used in subsequent
 147 .Fn sysctl
 148 calls to get the data associated with the requested ASCII name.
 149 This interface is intended for use by applications that want to
 150 repeatedly request the same variable (the
 151 .Fn sysctl
 152 function runs in about a third the time as the same request made via the
 153 .Fn sysctlbyname
 154 function).
 155 The
 156 .Fn sysctlbyname
 157 function is also useful for fetching mib prefixes and then adding
 158 a final component.
 159 For example, to fetch process information
 160 for processes with pid's less than 100:
 161 .Pp
 162 .Bd -literal -offset indent -compact
 163 int i, mib[4];
 164 size_t len;
 165 struct kinfo_proc kp;
 166
 167 /* Fill out the first three components of the mib */
 168 len = 4;
 169 sysctlnametomib("kern.proc.pid", mib, &len);
 170
 171 /* Fetch and print entries for pid's < 100 */
 172 for (i = 0; i < 100; i++) {
 173         mib[3] = i;
 174         len = sizeof(kp);
 175         if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
 176                 perror("sysctl");
 177         else if (len > 0)
 178                 printkproc(&kp);
 179 }
 180 .Ed
 181 .Pp
 182 The top level names are defined with a CTL_ prefix in
 183 .Aq Pa sys/sysctl.h ,
 184 and are as follows.
 185 The next and subsequent levels down are found in the include files
 186 listed here, and described in separate sections below.
 187 .Pp
 188 .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
 189 .It Sy "Name    Next level names        Description"
 190 .It "CTL\_DEBUG sys/sysctl.h    Debugging"
 191 .It "CTL\_VFS   sys/mount.h     Filesystem"
 192 .It "CTL\_HW    sys/sysctl.h    Generic CPU, I/O"
 193 .It "CTL\_KERN  sys/sysctl.h    High kernel limits"
 194 .It "CTL\_MACHDEP       sys/sysctl.h    Machine dependent"
 195 .It "CTL\_NET   sys/socket.h    Networking"
 196 .It "CTL\_USER  sys/sysctl.h    User-level"
 197 .It "CTL\_VM    vm/vm_param.h   Virtual memory"
 198 .El
 199 .Pp
 200 For example, the following retrieves the maximum number of processes allowed
 201 in the system:
 202 .Pp
 203 .Bd -literal -offset indent -compact
 204 int mib[2], maxproc;
 205 size_t len;
 206
 207 mib[0] = CTL_KERN;
 208 mib[1] = KERN_MAXPROC;
 209 len = sizeof(maxproc);
 210 sysctl(mib, 2, &maxproc, &len, NULL, 0);
 211 .Ed
 212 .Pp
 213 To retrieve the standard search path for the system utilities:
 214 .Pp
 215 .Bd -literal -offset indent -compact
 216 int mib[2];
 217 size_t len;
 218 char *p;
 219
 220 mib[0] = CTL_USER;
 221 mib[1] = USER_CS_PATH;
 222 sysctl(mib, 2, NULL, &len, NULL, 0);
 223 p = malloc(len);
 224 sysctl(mib, 2, p, &len, NULL, 0);
 225 .Ed
 226 .Ss CTL_DEBUG
 227 The debugging variables vary from system to system.
 228 A debugging variable may be added or deleted without need to recompile
 229 .Fn sysctl
 230 to know about it.
 231 Each time it runs,
 232 .Fn sysctl
 233 gets the list of debugging variables from the kernel and
 234 displays their current values.
 235 The system defines twenty
 236 .Ns ( Va struct ctldebug )
 237 variables named
 238 .Nm debug0
 239 through
 240 .Nm debug19 .
 241 They are declared as separate variables so that they can be
 242 individually initialized at the location of their associated variable.
 243 The loader prevents multiple use of the same variable by issuing errors
 244 if a variable is initialized in more than one place.
 245 For example, to export the variable
 246 .Nm dospecialcheck
 247 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 };
 251 .Ed
 252 .Ss CTL_VFS
 253 A distinguished second level name, VFS_GENERIC,
 254 is used to get general information about all filesystems.
 255 One of its third level identifiers is VFS_MAXTYPENUM
 256 that gives the highest valid filesystem type number.
 257 Its other third level identifier is VFS_CONF that
 258 returns configuration information about the filesystem
 259 type given as a fourth level identifier (see
 260 .Xr getvfsbyname 3
 261 as an example of its use).
 262 The remaining second level identifiers are the
 263 filesystem type number returned by a
 264 .Xr statfs 2
 265 call or from VFS_CONF.
 266 The third level identifiers available for each filesystem
 267 are given in the header file that defines the mount
 268 argument structure for that filesystem.
 269 .Ss CTL_HW
 270 The string and integer information available for the CTL_HW level
 271 is detailed below.
 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\_FLOATINGPOINT  integer no"
 284 .It "HW\_MACHINE\_ARCH  string  no"
 285 .\".It "HW\_DISKNAMES   integer no"
 286 .\".It "HW\_DISKSTATS   integer no"
 287 .El
 288 .Pp
 289 .Bl -tag -width 6n
 290 .It Li HW_MACHINE
 291 The machine class.
 292 .It Li HW_MODEL
 293 The machine model
 294 .It Li HW_NCPU
 295 The number of cpus.
 296 .It Li HW_BYTEORDER
 297 The byteorder (4,321, or 1,234).
 298 .It Li HW_PHYSMEM
 299 The bytes of physical memory.
 300 .It Li HW_USERMEM
 301 The bytes of non-kernel memory.
 302 .It Li HW_PAGESIZE
 303 The software page size.
 304 .It Li HW_FLOATINGPOINT
 305 Nonzero if the floating point support is in hardware.
 306 .It Li HW_MACHINE_ARCH
 307 The machine dependent architecture type.
 308 .\".It Fa HW_DISKNAMES
 309 .\".It Fa HW_DISKSTATS
 310 .El
 311 .Ss CTL_KERN
 312 The string and integer information available for the CTL_KERN level
 313 is detailed below.
 314 The changeable column shows whether a process with appropriate
 315 privilege may change the value.
 316 The types of data currently available are process information,
 317 system vnodes, the open file entries, routing table entries,
 318 virtual memory statistics, load average history, and clock rate
 319 information.
 320 .Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent
 321 .It Sy "Second level name       Type    Changeable"
 322 .It "KERN\_ARGMAX       integer no"
 323 .It "KERN\_BOOTFILE     string  yes"
 324 .It "KERN\_BOOTTIME     struct timeval  no"
 325 .It "KERN\_CLOCKRATE    struct clockinfo        no"
 326 .It "KERN\_FILE struct file     no"
 327 .It "KERN\_HOSTID       integer yes"
 328 .It "KERN\_HOSTNAME     string  yes"
 329 .It "KERN\_JOB\_CONTROL integer no"
 330 .It "KERN\_MAXFILES     integer yes"
 331 .It "KERN\_MAXFILESPERPROC      integer yes"
 332 .It "KERN\_MAXPROC      integer no"
 333 .It "KERN\_MAXPROCPERUID        integer yes"
 334 .It "KERN\_MAXVNODES    integer yes"
 335 .It "KERN\_NGROUPS      integer no"
 336 .It "KERN\_NISDOMAINNAME        string  yes"
 337 .It "KERN\_OSRELDATE    integer no"
 338 .It "KERN\_OSRELEASE    string  no"
 339 .It "KERN\_OSREV        integer no"
 340 .It "KERN\_OSTYPE       string  no"
 341 .It "KERN\_POSIX1       integer no"
 342 .It "KERN\_PROC struct proc     no"
 343 .It "KERN\_PROF node    not applicable"
 344 .It "KERN\_QUANTUM      integer yes"
 345 .It "KERN\_SAVED\_IDS   integer no"
 346 .It "KERN\_SECURELVL    integer raise only"
 347 .It "KERN\_UPDATEINTERVAL       integer no"
 348 .It "KERN\_VERSION      string  no"
 349 .It "KERN\_VNODE        struct vnode    no"
 350 .El
 351 .Pp
 352 .Bl -tag -width 6n
 353 .It Li KERN_ARGMAX
 354 The maximum bytes of argument to
 355 .Xr execve 2 .
 356 .It Li KERN_BOOTFILE
 357 The full pathname of the file from which the kernel was loaded.
 358 .It Li KERN_BOOTTIME
 359 A
 360 .Va struct timeval
 361 structure is returned.
 362 This structure contains the time that the system was booted.
 363 .It Li KERN_CLOCKRATE
 364 A
 365 .Va struct clockinfo
 366 structure is returned.
 367 This structure contains the clock, statistics clock and profiling clock
 368 frequencies, the number of micro-seconds per hz tick and the skew rate.
 369 .It Li KERN_FILE
 370 Return the entire file table.
 371 The returned data consists of a single
 372 .Va struct filehead
 373 followed by an array of
 374 .Va struct file ,
 375 whose size depends on the current number of such objects in the system.
 376 .It Li KERN_HOSTID
 377 Get or set the host id.
 378 .It Li KERN_HOSTNAME
 379 Get or set the hostname.
 380 .It Li KERN_JOB_CONTROL
 381 Return 1 if job control is available on this system, otherwise 0.
 382 .It Li KERN_MAXFILES
 383 The maximum number of files that may be open in the system.
 384 .It Li KERN_MAXFILESPERPROC
 385 The maximum number of files that may be open for a single process.
 386 This limit only applies to processes with an effective uid of nonzero
 387 at the time of the open request.
 388 Files that have already been opened are not affected if the limit
 389 or the effective uid is changed.
 390 .It Li KERN_MAXPROC
 391 The maximum number of concurrent processes the system will allow.
 392 .It Li KERN_MAXPROCPERUID
 393 The maximum number of concurrent processes the system will allow
 394 for a single effective uid.
 395 This limit only applies to processes with an effective uid of nonzero
 396 at the time of a fork request.
 397 Processes that have already been started are not affected if the limit
 398 is changed.
 399 .It Li KERN_MAXVNODES
 400 The maximum number of vnodes available on the system.
 401 .It Li KERN_NGROUPS
 402 The maximum number of supplemental groups.
 403 .It Li KERN_NISDOMAINNAME
 404 The name of the current YP/NIS domain.
 405 .It Li KERN_OSRELDATE
 406 The system release date in YYYYMM format
 407 (January 1996 is encoded as 199601).
 408 .It Li KERN_OSRELEASE
 409 The system release string.
 410 .It Li KERN_OSREV
 411 The system revision string.
 412 .It Li KERN_OSTYPE
 413 The system type string.
 414 .It Li KERN_POSIX1
 415 The version of
 416 .St -p1003.1
 417 with which the system
 418 attempts to comply.
 419 .It Li KERN_PROC
 420 Return the entire process table, or a subset of it.
 421 An array of pairs of
 422 .Va struct proc
 423 followed by corresponding
 424 .Va struct eproc
 425 structures is returned,
 426 whose size depends on the current number of such objects in the system.
 427 The third and fourth level names are as follows:
 428 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
 429 .It "Third level name   Fourth level is:"
 430 .It "KERN\_PROC\_ALL    None"
 431 .It "KERN\_PROC\_PID    A process ID"
 432 .It "KERN\_PROC\_PGRP   A process group"
 433 .It "KERN\_PROC\_TTY    A tty device"
 434 .It "KERN\_PROC\_UID    A user ID"
 435 .It "KERN\_PROC\_RUID   A real user ID"
 436 .El
 437 .Pp
 438 If the third level name is KERN_PROC_ARGS then the command line argument
 439 array is returned in a flattened form, i.e. zero-terminated arguments
 440 follow each other.
 441 The total size of array is returned.
 442 It is also possible for a process to set its own process title this way.
 443 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
 444 .It Sy "Third level name        Fourth level is:"
 445 .It "KERN\_PROC\_ARGS   A process ID"
 446 .El
 447 .It Li KERN_PROF
 448 Return profiling information about the kernel.
 449 If the kernel is not compiled for profiling,
 450 attempts to retrieve any of the KERN_PROF values will
 451 fail with
 452 .Er EOPNOTSUPP .
 453 The third level names for the string and integer profiling information
 454 is detailed below.
 455 The changeable column shows whether a process with appropriate
 456 privilege may change the value.
 457 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
 458 .It Sy "Third level name        Type    Changeable"
 459 .It "GPROF\_STATE       integer yes"
 460 .It "GPROF\_COUNT       u_short[\|]     yes"
 461 .It "GPROF\_FROMS       u_short[\|]     yes"
 462 .It "GPROF\_TOS struct tostruct yes"
 463 .It "GPROF\_GMONPARAM   struct gmonparam        no"
 464 .El
 465 .Pp
 466 The variables are as follows:
 467 .Bl -tag -width 6n
 468 .It Li GPROF_STATE
 469 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
 470 is running or stopped.
 471 .It Li GPROF_COUNT
 472 Array of statistical program counter counts.
 473 .It Li GPROF_FROMS
 474 Array indexed by program counter of call-from points.
 475 .It Li GPROF_TOS
 476 Array of
 477 .Va struct tostruct
 478 describing destination of calls and their counts.
 479 .It Li GPROF_GMONPARAM
 480 Structure giving the sizes of the above arrays.
 481 .El
 482 .It Li KERN_QUANTUM
 483 The maximum period of time, in microseconds, for which a process is allowed
 484 to run without being preempted if other processes are in the run queue.
 485 .It Li KERN_SAVED_IDS
 486 Returns 1 if saved set-group and saved set-user ID is available.
 487 .It Li KERN_SECURELVL
 488 The system security level.
 489 This level may be raised by processes with appropriate privilege.
 490 It may not be lowered.
 491 .It Li KERN_VERSION
 492 The system version string.
 493 .It Li KERN_VNODE
 494 Return the entire vnode table.
 495 Note, the vnode table is not necessarily a consistent snapshot of
 496 the system.
 497 The returned data consists of an array whose size depends on the
 498 current number of such objects in the system.
 499 Each element of the array contains the kernel address of a vnode
 500 .Va struct vnode *
 501 followed by the vnode itself
 502 .Va struct vnode .
 503 .El
 504 .Ss CTL_MACHDEP
 505 The set of variables defined is architecture dependent.
 506 The following variables are defined for the i386 architecture.
 507 .Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent
 508 .It Sy "Second level name       Type    Changeable"
 509 .It Li "CPU_CONSDEV     dev_t   no"
 510 .It Li "CPU_ADJKERNTZ   int     yes"
 511 .It Li "CPU_DISRTCSET   int     yes"
 512 .It Li "CPU_BOOTINFO    struct bootinfo no"
 513 .It Li "CPU_WALLCLOCK   int     yes"
 514 .El
 515 .Ss CTL_NET
 516 The string and integer information available for the CTL_NET level
 517 is detailed below.
 518 The changeable column shows whether a process with appropriate
 519 privilege may change the value.
 520 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
 521 .It Sy "Second level name       Type    Changeable"
 522 .It "PF\_ROUTE  routing messages        no"
 523 .It "PF\_INET   IPv4 values     yes"
 524 .It "PF\_INET6  IPv6 values     yes"
 525 .El
 526 .Pp
 527 .Bl -tag -width 6n
 528 .It Li PF_ROUTE
 529 Return the entire routing table or a subset of it.
 530 The data is returned as a sequence of routing messages (see
 531 .Xr route 4
 532 for the header file, format and meaning).
 533 The length of each message is contained in the message header.
 534 .Pp
 535 The third level name is a protocol number, which is currently always 0.
 536 The fourth level name is an address family, which may be set to 0 to
 537 select all address families.
 538 The fifth and sixth level names are as follows:
 539 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
 540 .It Sy "Fifth level name        Sixth level is:"
 541 .It "NET\_RT\_FLAGS     rtflags"
 542 .It "NET\_RT\_DUMP      None"
 543 .It "NET\_RT\_IFLIST    None"
 544 .El
 545 .It Li PF_INET
 546 Get or set various global information about the IPv4
 547 (Internet Protocol version 4).
 548 The third level name is the protocol.
 549 The fourth level name is the variable name.
 550 The currently defined protocols and names are:
 551 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
 552 .It Sy "Protocol        Variable        Type    Changeable"
 553 .It "icmp       bmcastecho      integer yes"
 554 .It "icmp       maskrepl        integer yes"
 555 .It "ip forwarding      integer yes"
 556 .It "ip redirect        integer yes"
 557 .It "ip ttl     integer yes"
 558 .It "udp        checksum        integer yes"
 559 .El
 560 .Pp
 561 The variables are as follows:
 562 .Bl -tag -width 6n
 563 .It Li icmp.bmcastecho
 564 Returns 1 if an ICMP echo request to a broadcast or multicast address is
 565 to be answered.
 566 .It Li icmp.maskrepl
 567 Returns 1 if ICMP network mask requests are to be answered.
 568 .It Li ip.forwarding
 569 Returns 1 when IP forwarding is enabled for the host,
 570 meaning that the host is acting as a router.
 571 .It Li ip.redirect
 572 Returns 1 when ICMP redirects may be sent by the host.
 573 This option is ignored unless the host is routing IP packets,
 574 and should normally be enabled on all systems.
 575 .It Li ip.ttl
 576 The maximum time-to-live (hop count) value for an IP packet sourced by
 577 the system.
 578 This value applies to normal transport protocols, not to ICMP.
 579 .It Li udp.checksum
 580 Returns 1 when UDP checksums are being computed and checked.
 581 Disabling UDP checksums is strongly discouraged.
 582 .Pp
 583 For variables net.inet.*.ipsec, please refer to
 584 .Xr ipsec 4 .
 585 .El
 586 .It Li PF_INET6
 587 Get or set various global information about the IPv6
 588 (Internet Protocol version 6).
 589 The third level name is the protocol.
 590 The fourth level name is the variable name.
 591 .Pp
 592 For variables net.inet6.* please refer to
 593 .Xr inet6 4 .
 594 For variables net.inet6.*.ipsec6, please refer to
 595 .Xr ipsec 4 .
 596 .El
 597 .Ss CTL_USER
 598 The string and integer information available for the CTL_USER level
 599 is detailed below.
 600 The changeable column shows whether a process with appropriate
 601 privilege may change the value.
 602 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
 603 .It Sy "Second level name       Type    Changeable"
 604 .It "USER\_BC\_BASE\_MAX        integer no"
 605 .It "USER\_BC\_DIM\_MAX integer no"
 606 .It "USER\_BC\_SCALE\_MAX       integer no"
 607 .It "USER\_BC\_STRING\_MAX      integer no"
 608 .It "USER\_COLL\_WEIGHTS\_MAX   integer no"
 609 .It "USER\_CS\_PATH     string  no"
 610 .It "USER\_EXPR\_NEST\_MAX      integer no"
 611 .It "USER\_LINE\_MAX    integer no"
 612 .It "USER\_POSIX2\_CHAR\_TERM   integer no"
 613 .It "USER\_POSIX2\_C\_BIND      integer no"
 614 .It "USER\_POSIX2\_C\_DEV       integer no"
 615 .It "USER\_POSIX2\_FORT\_DEV    integer no"
 616 .It "USER\_POSIX2\_FORT\_RUN    integer no"
 617 .It "USER\_POSIX2\_LOCALEDEF    integer no"
 618 .It "USER\_POSIX2\_SW\_DEV      integer no"
 619 .It "USER\_POSIX2\_UPE  integer no"
 620 .It "USER\_POSIX2\_VERSION      integer no"
 621 .It "USER\_RE\_DUP\_MAX integer no"
 622 .It "USER\_STREAM\_MAX  integer no"
 623 .It "USER\_TZNAME\_MAX  integer no"
 624 .El
 625 .Bl -tag -width 6n
 626 .Pp
 627 .It Li USER_BC_BASE_MAX
 628 The maximum ibase/obase values in the
 629 .Xr bc 1
 630 utility.
 631 .It Li USER_BC_DIM_MAX
 632 The maximum array size in the
 633 .Xr bc 1
 634 utility.
 635 .It Li USER_BC_SCALE_MAX
 636 The maximum scale value in the
 637 .Xr bc 1
 638 utility.
 639 .It Li USER_BC_STRING_MAX
 640 The maximum string length in the
 641 .Xr bc 1
 642 utility.
 643 .It Li USER_COLL_WEIGHTS_MAX
 644 The maximum number of weights that can be assigned to any entry of
 645 the LC_COLLATE order keyword in the locale definition file.
 646 .It Li USER_CS_PATH
 647 Return a value for the
 648 .Ev PATH
 649 environment variable that finds all the standard utilities.
 650 .It Li USER_EXPR_NEST_MAX
 651 The maximum number of expressions that can be nested within
 652 parenthesis by the
 653 .Xr expr 1
 654 utility.
 655 .It Li USER_LINE_MAX
 656 The maximum length in bytes of a text-processing utility's input
 657 line.
 658 .It Li USER_POSIX2_CHAR_TERM
 659 Return 1 if the system supports at least one terminal type capable of
 660 all operations described in
 661 .St -p1003.2 ,
 662 otherwise 0.
 663 .It Li USER_POSIX2_C_BIND
 664 Return 1 if the system's C-language development facilities support the
 665 C-Language Bindings Option, otherwise 0.
 666 .It Li USER_POSIX2_C_DEV
 667 Return 1 if the system supports the C-Language Development Utilities Option,
 668 otherwise 0.
 669 .It Li USER_POSIX2_FORT_DEV
 670 Return 1 if the system supports the FORTRAN Development Utilities Option,
 671 otherwise 0.
 672 .It Li USER_POSIX2_FORT_RUN
 673 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
 674 otherwise 0.
 675 .It Li USER_POSIX2_LOCALEDEF
 676 Return 1 if the system supports the creation of locales, otherwise 0.
 677 .It Li USER_POSIX2_SW_DEV
 678 Return 1 if the system supports the Software Development Utilities Option,
 679 otherwise 0.
 680 .It Li USER_POSIX2_UPE
 681 Return 1 if the system supports the User Portability Utilities Option,
 682 otherwise 0.
 683 .It Li USER_POSIX2_VERSION
 684 The version of
 685 .St -p1003.2
 686 with which the system attempts to comply.
 687 .It Li USER_RE_DUP_MAX
 688 The maximum number of repeated occurrences of a regular expression
 689 permitted when using interval notation.
 690 .It Li USER_STREAM_MAX
 691 The minimum maximum number of streams that a process may have open
 692 at any one time.
 693 .It Li USER_TZNAME_MAX
 694 The minimum maximum number of types supported for the name of a
 695 timezone.
 696 .El
 697 .Ss CTL_VM
 698 The string and integer information available for the CTL_VM level
 699 is detailed below.
 700 The changeable column shows whether a process with appropriate
 701 privilege may change the value.
 702 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
 703 .It Sy "Second level name       Type    Changeable"
 704 .It "VM\_LOADAVG        struct loadavg  no"
 705 .It "VM\_METER  struct vmtotal  no"
 706 .It "VM\_PAGEOUT\_ALGORITHM     integer yes"
 707 .It "VM\_SWAPPING\_ENABLED      integer maybe"
 708 .It "VM\_V\_CACHE\_MAX  integer yes"
 709 .It "VM\_V\_CACHE\_MIN  integer yes"
 710 .It "VM\_V\_FREE\_MIN   integer yes"
 711 .It "VM\_V\_FREE\_RESERVED      integer yes"
 712 .It "VM\_V\_FREE\_TARGET        integer yes"
 713 .It "VM\_V\_INACTIVE\_TARGET    integer yes"
 714 .It "VM\_V\_PAGEOUT\_FREE\_MIN  integer yes"
 715 .El
 716 .Pp
 717 .Bl -tag -width 6n
 718 .It Li VM_LOADAVG
 719 Return the load average history.
 720 The returned data consists of a
 721 .Va struct loadavg .
 722 .It Li VM_METER
 723 Return the system wide virtual memory statistics.
 724 The returned data consists of a
 725 .Va struct vmtotal .
 726 .It Li VM_PAGEOUT_ALGORITHM
 727 0 if the statistics-based page management algorithm is in use
 728 or 1 if the near-LRU algorithm is in use.
 729 .It Li VM_SWAPPING_ENABLED
 730 1 if process swapping is enabled or 0 if disabled.  This variable is
 731 permanently set to 0 if the kernel was built with swapping disabled.
 732 .It Li VM_V_CACHE_MAX
 733 Maximum desired size of the cache queue.
 734 .It Li VM_V_CACHE_MIN
 735 Minimum desired size of the cache queue.  If the cache queue size
 736 falls very far below this value, the pageout daemon is awakened.
 737 .It Li VM_V_FREE_MIN
 738 Minimum amount of memory (cache memory plus free memory)
 739 required to be available before a process waiting on memory will be
 740 awakened.
 741 .It Li VM_V_FREE_RESERVED
 742 Processes will awaken the pageout daemon and wait for memory if the
 743 number of free and cached pages drops below this value.
 744 .It Li VM_V_FREE_TARGET
 745 The total amount of free memory (including cache memory) that the
 746 pageout daemon tries to maintain.
 747 .It Li VM_V_INACTIVE_TARGET
 748 The desired number of inactive pages that the pageout daemon should
 749 achieve when it runs.  Inactive pages can be quickly inserted into
 750 process address space when needed.
 751 .It Li VM_V_PAGEOUT_FREE_MIN
 752 If the amount of free and cache memory falls below this value, the
 753 pageout daemon will enter "memory conserving mode" to avoid deadlock.
 754 .El
 755 .Sh RETURN VALUES
 756 .Rv -std
 757 .Sh ERRORS
 758 The following errors may be reported:
 759 .Bl -tag -width Er
 760 .It Bq Er EFAULT
 761 The buffer
 762 .Fa name ,
 763 .Fa oldp ,
 764 .Fa newp ,
 765 or length pointer
 766 .Fa oldlenp
 767 contains an invalid address.
 768 .It Bq Er EINVAL
 769 The
 770 .Fa name
 771 array is less than two or greater than CTL_MAXNAME.
 772 .It Bq Er EINVAL
 773 A non-null
 774 .Fa newp
 775 is given and its specified length in
 776 .Fa newlen
 777 is too large or too small.
 778 .It Bq Er ENOMEM
 779 The length pointed to by
 780 .Fa oldlenp
 781 is too short to hold the requested value.
 782 .It Bq Er ENOTDIR
 783 The
 784 .Fa name
 785 array specifies an intermediate rather than terminal name.
 786 .It Bq Er EISDIR
 787 The
 788 .Fa name
 789 array specifies a terminal name, but the actual name is not terminal.
 790 .It Bq Er EOPNOTSUPP
 791 The
 792 .Fa name
 793 array specifies a value that is unknown.
 794 .It Bq Er EPERM
 795 An attempt is made to set a read-only value.
 796 .It Bq Er EPERM
 797 A process without appropriate privilege attempts to set a value.
 798 .El
 799 .Sh FILES
 800 .Bl -tag -width <netinet/icmpXvar.h> -compact
 801 .It Aq Pa sys/sysctl.h
 802 definitions for top level identifiers, second level kernel and hardware
 803 identifiers, and user level identifiers
 804 .It Aq Pa sys/socket.h
 805 definitions for second level network identifiers
 806 .It Aq Pa sys/gmon.h
 807 definitions for third level profiling identifiers
 808 .It Aq Pa vm/vm_param.h
 809 definitions for second level virtual memory identifiers
 810 .It Aq Pa netinet/in.h
 811 definitions for third level IPv4/IPv6 identifiers and
 812 fourth level IPv4/v6 identifiers
 813 .It Aq Pa netinet/icmp_var.h
 814 definitions for fourth level ICMP identifiers
 815 .It Aq Pa netinet/icmp6.h
 816 definitions for fourth level ICMPv6 identifiers
 817 .It Aq Pa netinet/udp_var.h
 818 definitions for fourth level UDP identifiers
 819 .El
 820 .Sh SEE ALSO
 821 .Xr sysconf 3 ,
 822 .Xr sysctl 8
 823 .Sh HISTORY
 824 The
 825 .Fn sysctl
 826 function first appeared in
 827 .Bx 4.4 .