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 8.1 (Berkeley) 6/4/93 33.\" 34.Dd "June 4, 1993" 35.Dt SYSCTL 3 36.Os 37.Sh NAME 38.Nm sysctl 39.Nd get or set system information 40.Sh SYNOPSIS 41.Fd #include <sys/types.h> 42.Fd #include <sys/sysctl.h> 43.Ft int 44.Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen" 45.Sh DESCRIPTION 46The 47.Fn sysctl 48function retrieves system information and allows processes with 49appropriate privileges to set system information. 50The information available from 51.Fn sysctl 52consists of integers, strings, and tables. 53Information may be retrieved and set from the command interface 54using the 55.Xr sysctl 8 56utility. 57.Pp 58Unless explicitly noted below, 59.Fn sysctl 60returns a consistent snapshot of the data requested. 61Consistency is obtained by locking the destination 62buffer into memory so that the data may be copied out without blocking. 63Calls to 64.Fn sysctl 65are serialized to avoid deadlock. 66.Pp 67The state is described using a ``Management Information Base'' (MIB) 68style name, listed in 69.Fa name , 70which is a 71.Fa namelen 72length array of integers. 73.Pp 74The information is copied into the buffer specified by 75.Fa oldp . 76The size of the buffer is given by the location specified by 77.Fa oldlenp 78before the call, 79and that location gives the amount of data copied after a successful call. 80If the amount of data available is greater 81than the size of the buffer supplied, 82the call supplies as much data as fits in the buffer provided 83and returns with the error code ENOMEM. 84If the old value is not desired, 85.Fa oldp 86and 87.Fa oldlenp 88should be set to NULL. 89.Pp 90The size of the available data can be determined by calling 91.Fn sysctl 92with a NULL parameter for 93.Fa oldp . 94The size of the available data will be returned in the location pointed to by 95.Fa oldlenp . 96For some operations, the amount of space may change often. 97For these operations, 98the system attempts to round up so that the returned size is 99large enough for a call to return the data shortly thereafter. 100.Pp 101To set a new value, 102.Fa newp 103is set to point to a buffer of length 104.Fa newlen 105from which the requested value is to be taken. 106If a new value is not to be set, 107.Fa newp 108should be set to NULL and 109.Fa newlen 110set to 0. 111.Pp 112The top level names are defined with a CTL_ prefix in 113.Pa <sys/sysctl.h> , 114and are as follows. 115The next and subsequent levels down are found in the include files 116listed here, and described in separate sections below. 117.Pp 118.Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent 119.It Sy Pa Name Next level names Description 120.It CTL\_DEBUG sys/sysctl.h Debugging 121.It CTL\_VFS sys/sysctl.h File system 122.It CTL\_HW sys/sysctl.h Generic CPU, I/O 123.It CTL\_KERN sys/sysctl.h High kernel limits 124.It CTL\_MACHDEP sys/sysctl.h Machine dependent 125.It CTL\_NET sys/socket.h Networking 126.It CTL\_USER sys/sysctl.h User-level 127.It CTL\_VM vm/vm_param.h Virtual memory 128.El 129.Pp 130For example, the following retrieves the maximum number of processes allowed 131in the system: 132.Bd -literal -offset indent -compact 133int mib[2], maxproc; 134size_t len; 135.sp 136mib[0] = CTL_KERN; 137mib[1] = KERN_MAXPROC; 138len = sizeof(maxproc); 139sysctl(mib, 2, &maxproc, &len, NULL, 0); 140.Ed 141.sp 142To retrieve the standard search path for the system utilities: 143.Bd -literal -offset indent -compact 144int mib[2]; 145size_t len; 146char *p; 147.sp 148mib[0] = CTL_USER; 149mib[1] = USER_CS_PATH; 150sysctl(mib, 2, NULL, &len, NULL, 0); 151p = malloc(len); 152sysctl(mib, 2, p, &len, NULL, 0); 153.Ed 154.Sh CTL_DEBUG 155The debugging variables vary from system to system. 156A debugging variable may be added or deleted without need to recompile 157.Fn sysctl 158to know about it. 159Each time it runs, 160.Fn sysctl 161gets the list of debugging variables from the kernel and 162displays their current values. 163The system defines twenty 164.Ns ( Va struct ctldebug ) 165variables named 166.Nm debug0 167through 168.Nm debug19 . 169They are declared as separate variables so that they can be 170individually initialized at the location of their associated variable. 171The loader prevents multiple use of the same variable by issuing errors 172if a variable is initialized in more than one place. 173For example, to export the variable 174.Nm dospecialcheck 175as a debugging variable, the following declaration would be used: 176.Bd -literal -offset indent -compact 177int dospecialcheck = 1; 178struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; 179.Ed 180.Sh CTL_VFS 181There are currently no second level names for the file system. 182.Sh CTL_HW 183The string and integer information available for the CTL_HW level 184is detailed below. 185The changeable column shows whether a process with appropriate 186privilege may change the value. 187.Bl -column "Second level nameXXXXXX" integerXXX -offset indent 188.It Sy Pa Second level name Type Changeable 189.It HW\_MACHINE string no 190.It HW\_MODEL string no 191.It HW\_NCPU integer no 192.It HW\_BYTEORDER integer no 193.It HW\_PHYSMEM integer no 194.It HW\_USERMEM integer no 195.It HW\_PAGESIZE integer no 196.It HW\_FLOATINGPOINT integer no 197.\".It HW\_DISKNAMES integer no 198.\".It HW\_DISKSTATS integer no 199.El 200.Pp 201.Bl -tag -width "123456" 202.It Li HW_MACHINE 203The machine class. 204.It Li HW_MODEL 205The machine model 206.It Li HW_NCPU 207The number of cpus. 208.It Li HW_BYTEORDER 209The byteorder (4,321, or 1,234). 210.It Li HW_PHYSMEM 211The bytes of physical memory. 212.It Li HW_USERMEM 213The bytes of non-kernel memory. 214.It Li HW_PAGESIZE 215The software page size. 216.It Li HW_FLOATINGPOINT 217Nonzero if the floating point support is in hardware. 218.\".It Fa HW_DISKNAMES 219.\".It Fa HW_DISKSTATS 220.El 221.Sh CTL_KERN 222The string and integer information available for the CTL_KERN level 223is detailed below. 224The changeable column shows whether a process with appropriate 225privilege may change the value. 226The types of data currently available are process information, 227system vnodes, the open file entries, routing table entries, 228virtual memory statistics, load average history, and clock rate 229information. 230.Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent 231.It Sy Pa Second level name Type Changeable 232.It KERN\_ARGMAX integer no 233.It KERN\_BOOTFILE string yes 234.It KERN\_BOOTTIME struct timeval no 235.It KERN\_CLOCKRATE struct clockinfo no 236.It KERN\_FILE struct file no 237.It KERN\_HOSTID integer yes 238.It KERN\_HOSTNAME string yes 239.It KERN\_JOB\_CONTROL integer no 240.It KERN\_MAXFILES integer yes 241.It KERN\_MAXFILESPERPROC integer yes 242.It KERN\_MAXPROC integer yes 243.It KERN\_MAXPROCPERUID integer yes 244.It KERN\_MAXVNODES integer yes 245.It KERN\_NGROUPS integer no 246.It KERN\_NISDOMAINNAME string yes 247.It KERN\_OSRELDATE integer no 248.It KERN\_OSRELEASE string no 249.It KERN\_OSREV integer no 250.It KERN\_OSTYPE string no 251.It KERN\_POSIX1 integer no 252.It KERN\_PROC struct proc no 253.It KERN\_PROF node not applicable 254.It KERN\_SAVED\_IDS integer no 255.It KERN\_SECURELVL integer raise only 256.It KERN\_UPDATEINTERVAL integer no 257.It KERN\_VERSION string no 258.It KERN\_VNODE struct vnode no 259.El 260.Pp 261.Bl -tag -width "123456" 262.It Li KERN_ARGMAX 263The maximum bytes of argument to 264.Xr execve 2 . 265.It Li KERN_BOOTFILE 266The full pathname of the file from which the kernel was loaded. 267.It Li KERN_BOOTTIME 268A 269.Va struct timeval 270structure is returned. 271This structure contains the time that the system was booted. 272.It Li KERN_CLOCKRATE 273A 274.Va struct clockinfo 275structure is returned. 276This structure contains the clock, statistics clock and profiling clock 277frequencies, and the number of micro-seconds per hz tick. 278.It Li KERN_FILE 279Return the entire file table. 280The returned data consists of a single 281.Va struct filehead 282followed by an array of 283.Va struct file , 284whose size depends on the current number of such objects in the system. 285.It Li KERN_HOSTID 286Get or set the host id. 287.It Li KERN_HOSTNAME 288Get or set the hostname. 289.It Li KERN_JOB_CONTROL 290Return 1 if job control is available on this system, otherwise 0. 291.It Li KERN_MAXFILES 292The maximum number of files that may be open in the system. 293.It Li KERN_MAXFILESPERPROC 294The maximum number of files that may be open for a single process. 295This limit only applies to processes with an effective uid of nonzero 296at the time of the open request. 297Files that have already been opened are not affected if the limit 298or the effective uid is changed. 299.It Li KERN_MAXPROC 300The maximum number of concurrent processes the system will allow. 301.It Li KERN_MAXPROCPERUID 302The maximum number of concurrent processes the system will allow 303for a single effective uid. 304This limit only applies to processes with an effective uid of nonzero 305at the time of a fork request. 306Processes that have already been started are not affected if the limit 307is changed. 308.It Li KERN_MAXVNODES 309The maximum number of vnodes available on the system. 310.It Li KERN_NGROUPS 311The maximum number of supplemental groups. 312.It Li KERN_NISDOMAINNAME 313The name of the current YP/NIS domain. 314.It Li KERN_OSRELDATE 315The system release date in YYYYMM format 316(January 1996 is encoded as 199601). 317.It Li KERN_OSRELEASE 318The system release string. 319.It Li KERN_OSREV 320The system revision string. 321.It Li KERN_OSTYPE 322The system type string. 323.It Li KERN_POSIX1 324The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 325attempts to comply. 326.It Li KERN_PROC 327Return the entire process table, or a subset of it. 328An array of 329.Va struct kinfo_proc 330structures is returned, 331whose size depends on the current number of such objects in the system. 332The third and fourth level names are as follows: 333.Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent 334.It Pa Third level name Fourth level is: 335.It KERN\_PROC\_ALL None 336.It KERN\_PROC\_PID A process ID 337.It KERN\_PROC\_PGRP A process group 338.It KERN\_PROC\_TTY A tty device 339.It KERN\_PROC\_UID A user ID 340.It KERN\_PROC\_RUID A real user ID 341.El 342.It Li KERN_PROF 343Return profiling information about the kernel. 344If the kernel is not compiled for profiling, 345attempts to retrieve any of the KERN_PROF values will 346fail with EOPNOTSUPP. 347The third level names for the string and integer profiling information 348is detailed below. 349The changeable column shows whether a process with appropriate 350privilege may change the value. 351.Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent 352.It Sy Pa Third level name Type Changeable 353.It GPROF\_STATE integer yes 354.It GPROF\_COUNT u_short[\|] yes 355.It GPROF\_FROMS u_short[\|] yes 356.It GPROF\_TOS struct tostruct yes 357.It GPROF\_GMONPARAM struct gmonparam no 358.El 359.Pp 360The variables are as follows: 361.Bl -tag -width "123456" 362.It Li GPROF_STATE 363Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling 364is running or stopped. 365.It Li GPROF_COUNT 366Array of statistical program counter counts. 367.It Li GPROF_FROMS 368Array indexed by program counter of call-from points. 369.It Li GPROF_TOS 370Array of 371.Va struct tostruct 372describing destination of calls and their counts. 373.It Li GPROF_GMONPARAM 374Structure giving the sizes of the above arrays. 375.El 376.It Li KERN_SAVED_IDS 377Returns 1 if saved set-group and saved set-user ID is available. 378.It Li KERN_SECURELVL 379The system security level. 380This level may be raised by processes with appropriate privilege. 381It may only be lowered by process 1. 382.It Li KERN_VERSION 383The system version string. 384.It Li KERN_VNODE 385Return the entire vnode table. 386Note, the vnode table is not necessarily a consistent snapshot of 387the system. 388The returned data consists of an array whose size depends on the 389current number of such objects in the system. 390Each element of the array contains the kernel address of a vnode 391.Va struct vnode * 392followed by the vnode itself 393.Va struct vnode . 394.It Li KERN_UPDATEINTERVAL 395The interval between 396.Xr sync 2 397calls in the 398.Xr update 4 399process. 400.El 401.Sh CTL_MACHDEP 402The set of variables defined is architecture dependent. 403The following variables are defined for the i386 architecture. 404.Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent 405.It Sy Pa Second level name Type Changeable 406.It Li CPU_CONSDEV dev_t no 407.It Li CPU_ADJKERNTZ int yes 408.It Li CPU_DISRTCSET int yes 409.It Li CPU_BOOTINFO struct bootinfo no 410.It Li CPU_WALLCLOCK int yes 411.El 412.Sh CTL_NET 413The string and integer information available for the CTL_NET level 414is detailed below. 415The changeable column shows whether a process with appropriate 416privilege may change the value. 417.Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent 418.It Sy Pa Second level name Type Changeable 419.It PF\_ROUTE routing messages no 420.It PF\_INET internet values yes 421.El 422.Pp 423.Bl -tag -width "123456" 424.It Li PF_ROUTE 425Return the entire routing table or a subset of it. 426The data is returned as a sequence of routing messages (see 427.Xr route 4 428for the header file, format and meaning). 429The length of each message is contained in the message header. 430.Pp 431The third level name is a protocol number, which is currently always 0. 432The fourth level name is an address family, which may be set to 0 to 433select all address families. 434The fifth and sixth level names are as follows: 435.Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent 436.It Pa Fifth level name Sixth level is: 437.It NET\_RT\_FLAGS rtflags 438.It NET\_RT\_DUMP None 439.It NET\_RT\_IFLIST None 440.El 441.It Li PF_INET 442Get or set various global information about the internet protocols. 443The third level name is the protocol. 444The fourth level name is the variable name. 445The currently defined protocols and names are: 446.Bl -column "Protocol nameXXXXXX" "Variable nameXXX" "integerXXX" -offset indent 447.It Pa Protocol name Variable name Type Changeable 448.It ip forwarding integer yes 449.It ip redirect integer yes 450.It ip ttl integer yes 451.It icmp maskrepl integer yes 452.It udp checksum integer yes 453.El 454.Pp 455The variables are as follows: 456.Bl -tag -width "123456" 457.It Li ip.forwarding 458Returns 1 when IP forwarding is enabled for the host, 459meaning that the host is acting as a router. 460.It Li ip.redirect 461Returns 1 when ICMP redirects may be sent by the host. 462This option is ignored unless the host is routing IP packets, 463and should normally be enabled on all systems. 464.It Li ip.ttl 465The maximum time-to-live (hop count) value for an IP packet sourced by 466the system. 467This value applies to normal transport protocols, not to ICMP. 468.It Li icmp.maskrepl 469Returns 1 if ICMP network mask requests are to be answered. 470.It Li udp.checksum 471Returns 1 when UDP checksums are being computed and checked. 472Disabling UDP checksums is strongly discouraged. 473.El 474.Sh CTL_USER 475The string and integer information available for the CTL_USER level 476is detailed below. 477The changeable column shows whether a process with appropriate 478privilege may change the value. 479.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent 480.It Sy Pa Second level name Type Changeable 481.It USER\_BC\_BASE\_MAX integer no 482.It USER\_BC\_DIM\_MAX integer no 483.It USER\_BC\_SCALE\_MAX integer no 484.It USER\_BC\_STRING\_MAX integer no 485.It USER\_COLL\_WEIGHTS\_MAX integer no 486.It USER\_CS\_PATH string no 487.It USER\_EXPR\_NEST\_MAX integer no 488.It USER\_LINE\_MAX integer no 489.It USER\_POSIX2\_CHAR\_TERM integer no 490.It USER\_POSIX2\_C\_BIND integer no 491.It USER\_POSIX2\_C\_DEV integer no 492.It USER\_POSIX2\_FORT\_DEV integer no 493.It USER\_POSIX2\_FORT\_RUN integer no 494.It USER\_POSIX2\_LOCALEDEF integer no 495.It USER\_POSIX2\_SW\_DEV integer no 496.It USER\_POSIX2\_UPE integer no 497.It USER\_POSIX2\_VERSION integer no 498.It USER\_RE\_DUP\_MAX integer no 499.It USER\_STREAM\_MAX integer no 500.It USER\_TZNAME\_MAX integer no 501.El 502.Bl -tag -width "123456" 503.Pp 504.It Li USER_BC_BASE_MAX 505The maximum ibase/obase values in the 506.Xr bc 1 507utility. 508.It Li USER_BC_DIM_MAX 509The maximum array size in the 510.Xr bc 1 511utility. 512.It Li USER_BC_SCALE_MAX 513The maximum scale value in the 514.Xr bc 1 515utility. 516.It Li USER_BC_STRING_MAX 517The maximum string length in the 518.Xr bc 1 519utility. 520.It Li USER_COLL_WEIGHTS_MAX 521The maximum number of weights that can be assigned to any entry of 522the LC_COLLATE order keyword in the locale definition file. 523.It Li USER_CS_PATH 524Return a value for the 525.Ev PATH 526environment variable that finds all the standard utilities. 527.It Li USER_EXPR_NEST_MAX 528The maximum number of expressions that can be nested within 529parenthesis by the 530.Xr expr 1 531utility. 532.It Li USER_LINE_MAX 533The maximum length in bytes of a text-processing utility's input 534line. 535.It Li USER_POSIX2_CHAR_TERM 536Return 1 if the system supports at least one terminal type capable of 537all operations described in POSIX 1003.2, otherwise 0. 538.It Li USER_POSIX2_C_BIND 539Return 1 if the system's C-language development facilities support the 540C-Language Bindings Option, otherwise 0. 541.It Li USER_POSIX2_C_DEV 542Return 1 if the system supports the C-Language Development Utilities Option, 543otherwise 0. 544.It Li USER_POSIX2_FORT_DEV 545Return 1 if the system supports the FORTRAN Development Utilities Option, 546otherwise 0. 547.It Li USER_POSIX2_FORT_RUN 548Return 1 if the system supports the FORTRAN Runtime Utilities Option, 549otherwise 0. 550.It Li USER_POSIX2_LOCALEDEF 551Return 1 if the system supports the creation of locales, otherwise 0. 552.It Li USER_POSIX2_SW_DEV 553Return 1 if the system supports the Software Development Utilities Option, 554otherwise 0. 555.It Li USER_POSIX2_UPE 556Return 1 if the system supports the User Portability Utilities Option, 557otherwise 0. 558.It Li USER_POSIX2_VERSION 559The version of POSIX 1003.2 with which the system attempts to comply. 560.It Li USER_RE_DUP_MAX 561The maximum number of repeated occurrences of a regular expression 562permitted when using interval notation. 563.It Li USER_STREAM_MAX 564The minimum maximum number of streams that a process may have open 565at any one time. 566.It Li USER_TZNAME_MAX 567The minimum maximum number of types supported for the name of a 568timezone. 569.El 570.Sh CTL_VM 571The string and integer information available for the CTL_VM level 572is detailed below. 573The changeable column shows whether a process with appropriate 574privilege may change the value. 575.Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent 576.It Sy Pa Second level name Type Changeable 577.It VM\_LOADAVG struct loadavg no 578.It VM\_METER struct vmtotal no 579.El 580.Pp 581.Bl -tag -width "123456" 582.It Li VM_LOADAVG 583Return the load average history. 584The returned data consists of a 585.Va struct loadavg . 586.It Li VM_METER 587Return the system wide virtual memory statistics. 588The returned data consists of a 589.Va struct vmtotal . 590.El 591.Sh RETURN VALUES 592If the call to 593.Fn sysctl 594is successful, 0 is returned. 595Otherwise \-1 is returned and 596.Va errno 597is set appropriately. 598.Sh ERRORS 599The following errors may be reported: 600.Bl -tag -width Er 601.It Bq Er EFAULT 602The buffer 603.Fa name , 604.Fa oldp , 605.Fa newp , 606or length pointer 607.Fa oldlenp 608contains an invalid address. 609.It Bq Er EINVAL 610The 611.Fa name 612array is less than two or greater than CTL_MAXNAME. 613.It Bq Er EINVAL 614A non-null 615.Fa newp 616is given and its specified length in 617.Fa newlen 618is too large or too small. 619.It Bq Er ENOMEM 620The length pointed to by 621.Fa oldlenp 622is too short to hold the requested value. 623.It Bq Er ENOTDIR 624The 625.Fa name 626array specifies an intermediate rather than terminal name. 627.It Bq Er EOPNOTSUPP 628The 629.Fa name 630array specifies a value that is unknown. 631.It Bq Er EPERM 632An attempt is made to set a read-only value. 633.It Bq Er EPERM 634A process without appropriate privilege attempts to set a value. 635.El 636.Sh FILES 637.Bl -tag -width <netinet/icmpXvar.h> -compact 638.It Pa <sys/sysctl.h> 639definitions for top level identifiers, second level kernel and hardware 640identifiers, and user level identifiers 641.It Pa <sys/socket.h> 642definitions for second level network identifiers 643.It Pa <sys/gmon.h> 644definitions for third level profiling identifiers 645.It Pa <vm/vm_param.h> 646definitions for second level virtual memory identifiers 647.It Pa <netinet/in.h> 648definitions for third level Internet identifiers and 649fourth level IP identifiers 650.It Pa <netinet/icmp_var.h> 651definitions for fourth level ICMP identifiers 652.It Pa <netinet/udp_var.h> 653definitions for fourth level UDP identifiers 654.El 655.Sh SEE ALSO 656.Xr sysctl 8 657.Sh HISTORY 658The 659.Fn sysctl 660function first appeared in 661.Bx 4.4 . 662