1.\" $NetBSD: sysctl.3,v 1.11 1996/07/17 18:06:36 explorer Exp $ 2.\" 3.\" Copyright (c) 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)sysctl.3 8.1 (Berkeley) 6/4/93 35.\" 36.Dd "June 4, 1993" 37.Dt SYSCTL 3 38.Os 39.Sh NAME 40.Nm sysctl 41.Nd get or set system information 42.Sh SYNOPSIS 43.Fd #include <sys/param.h> 44.Fd #include <sys/sysctl.h> 45.Ft int 46.Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen" 47.Sh DESCRIPTION 48The 49.Nm sysctl 50function retrieves system information and allows processes with 51appropriate privileges to set system information. 52The information available from 53.Nm sysctl 54consists of integers, strings, and tables. 55Information may be retrieved and set from the command interface 56using the 57.Xr sysctl 8 58utility. 59.Pp 60Unless explicitly noted below, 61.Nm sysctl 62returns a consistent snapshot of the data requested. 63Consistency is obtained by locking the destination 64buffer into memory so that the data may be copied out without blocking. 65Calls to 66.Nm sysctl 67are serialized to avoid deadlock. 68.Pp 69The state is described using a ``Management Information Base'' (MIB) 70style name, listed in 71.Fa name , 72which is a 73.Fa namelen 74length array of integers. 75.Pp 76The information is copied into the buffer specified by 77.Fa oldp . 78The size of the buffer is given by the location specified by 79.Fa oldlenp 80before the call, 81and that location gives the amount of data copied after a successful call. 82If the amount of data available is greater 83than the size of the buffer supplied, 84the call supplies as much data as fits in the buffer provided 85and returns with the error code ENOMEM. 86If the old value is not desired, 87.Fa oldp 88and 89.Fa oldlenp 90should be set to NULL. 91.Pp 92The size of the available data can be determined by calling 93.Nm sysctl 94with a NULL parameter for 95.Fa oldp . 96The size of the available data will be returned in the location pointed to by 97.Fa oldlenp . 98For some operations, the amount of space may change often. 99For these operations, 100the system attempts to round up so that the returned size is 101large enough for a call to return the data shortly thereafter. 102.Pp 103To set a new value, 104.Fa newp 105is set to point to a buffer of length 106.Fa newlen 107from which the requested value is to be taken. 108If a new value is not to be set, 109.Fa newp 110should be set to NULL and 111.Fa newlen 112set to 0. 113.Pp 114The top level names are defined with a CTL_ prefix in 115.Pa <sys/sysctl.h> , 116and are as follows. 117The next and subsequent levels down are found in the include files 118listed here, and described in separate sections below. 119.Pp 120.Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent 121.It Sy Pa Name Next level names Description 122.It CTL\_DEBUG sys/sysctl.h Debugging 123.It CTL\_FS sys/sysctl.h File system 124.It CTL\_HW sys/sysctl.h Generic CPU, I/O 125.It CTL\_KERN sys/sysctl.h High kernel limits 126.It CTL\_MACHDEP sys/sysctl.h Machine dependent 127.It CTL\_NET sys/socket.h Networking 128.It CTL\_USER sys/sysctl.h User-level 129.It CTL\_VM vm/vm_param.h Virtual memory 130.El 131.Pp 132For example, the following retrieves the maximum number of processes allowed 133in the system: 134.Bd -literal -offset indent -compact 135int mib[2], maxproc; 136size_t len; 137.sp 138mib[0] = CTL_KERN; 139mib[1] = KERN_MAXPROC; 140len = sizeof(maxproc); 141sysctl(mib, 2, &maxproc, &len, NULL, 0); 142.Ed 143.sp 144To retrieve the standard search path for the system utilities: 145.Bd -literal -offset indent -compact 146int mib[2]; 147size_t len; 148char *p; 149.sp 150mib[0] = CTL_USER; 151mib[1] = USER_CS_PATH; 152sysctl(mib, 2, NULL, &len, NULL, 0); 153p = malloc(len); 154sysctl(mib, 2, p, &len, NULL, 0); 155.Ed 156.Sh CTL_DEBUG 157The debugging variables vary from system to system. 158A debugging variable may be added or deleted without need to recompile 159.Nm sysctl 160to know about it. 161Each time it runs, 162.Nm sysctl 163gets the list of debugging variables from the kernel and 164displays their current values. 165The system defines twenty 166.Ns ( Va struct ctldebug ) 167variables named 168.Nm debug0 169through 170.Nm debug19 . 171They are declared as separate variables so that they can be 172individually initialized at the location of their associated variable. 173The loader prevents multiple use of the same variable by issuing errors 174if a variable is initialized in more than one place. 175For example, to export the variable 176.Nm dospecialcheck 177as a debugging variable, the following declaration would be used: 178.Bd -literal -offset indent -compact 179int dospecialcheck = 1; 180struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; 181.Ed 182.Sh CTL_FS 183There are currently no second level names for the file system. 184.Sh CTL_HW 185The string and integer information available for the CTL_HW level 186is detailed below. 187The changeable column shows whether a process with appropriate 188privilege may change the value. 189.Bl -column "Second level nameXXXXXX" integerXXX -offset indent 190.It Sy Pa Second level name Type Changeable 191.It HW\_MACHINE string no 192.It HW\_MODEL string no 193.It HW\_NCPU integer no 194.It HW\_BYTEORDER integer no 195.It HW\_PHYSMEM integer no 196.It HW\_USERMEM integer no 197.It HW\_PAGESIZE integer no 198.\".It HW\_DISKNAMES integer no 199.\".It HW\_DISKSTATS integer no 200.El 201.Pp 202.Bl -tag -width "123456" 203.It Li HW_MACHINE 204The machine class. 205.It Li HW_MODEL 206The machine model 207.It Li HW_NCPU 208The number of cpus. 209.It Li HW_BYTEORDER 210The byteorder (4,321, or 1,234). 211.It Li HW_PHYSMEM 212The bytes of physical memory. 213.It Li HW_USERMEM 214The bytes of non-kernel memory. 215.It Li HW_PAGESIZE 216The software page size. 217.\".It Fa HW_DISKNAMES 218.\".It Fa HW_DISKSTATS 219.El 220.Sh CTL_KERN 221The string and integer information available for the CTL_KERN level 222is detailed below. 223The changeable column shows whether a process with appropriate 224privilege may change the value. 225The types of data currently available are process information, 226system vnodes, the open file entries, routing table entries, 227virtual memory statistics, load average history, and clock rate 228information. 229.Bl -column "KERNXCHOWNXRESTRICTEDXXX" "struct clockrateXXX" -offset indent 230.It Sy Pa Second level name Type Changeable 231.It KERN\_ARGMAX integer no 232.It KERN\_AUTONICETIME integer yes 233.It KERN\_AUTONICEVAL integer yes 234.It KERN\_BOOTTIME struct timeval no 235.It KERN\_CHOWN\_RESTRICTED integer no 236.It KERN\_CLOCKRATE struct clockinfo no 237.It KERN\_DOMAINNAME string yes 238.It KERN\_FILE struct file no 239.It KERN\_HOSTID integer yes 240.It KERN\_HOSTNAME string yes 241.It KERN\_JOB\_CONTROL integer no 242.It KERN\_LINK\_MAX integer no 243.It KERN\_MAXFILES integer yes 244.It KERN\_MAXPARTITIONS integer no 245.It KERN\_MAXPROC integer yes 246.It KERN\_MAXVNODES integer yes 247.It KERN\_MAX\_CANON integer no 248.It KERN\_MAX\_INPUT integer no 249.It KERN\_NAME\_MAX integer no 250.It KERN\_NGROUPS integer no 251.It KERN\_NO\_TRUNC integer no 252.It KERN\_OSRELEASE string no 253.It KERN\_OSREV integer no 254.It KERN\_OSTYPE string no 255.It KERN\_PATH\_MAX integer no 256.It KERN\_PIPE\_BUF integer no 257.It KERN\_POSIX1 integer no 258.It KERN\_PROC struct proc no 259.It KERN\_PROF node not applicable 260.It KERN\_RAWPARTITION integer no 261.It KERN\_SAVED\_IDS integer no 262.It KERN\_SECURELVL integer raise only 263.It KERN\_VDISABLE integer no 264.It KERN\_VERSION string no 265.It KERN\_VNODE struct vnode no 266.El 267.Pp 268.Bl -tag -width "123456" 269.It Li KERN_ARGMAX 270The maximum bytes of argument to 271.Xr exec 2 . 272.It Li KERN_AUTONICETIME 273The number of seconds of cpu-time a non-root process may accumulate before 274having its priority lowered from the default to the value of KERN_AUTONICEVAL. 275If set to 0, automatic lowering of priority is not performed, and if set to -1 276all non-root processes are immediately lowered. 277.It Li KERN_AUTONICEVAL 278The priority assigned for automatically niced processes. 279.It Li KERN_BOOTTIME 280A 281.Va struct timeval 282structure is returned. 283This structure contains the time that the system was booted. 284.It Li KERN_CHOWN_RESTRICTED 285Return 1 if appropriate privileges are required for the 286.Xr chown 2 287system call, otherwise 0. 288.It Li KERN_CLOCKRATE 289A 290.Va struct clockinfo 291structure is returned. 292This structure contains the clock, statistics clock and profiling clock 293frequencies, the number of micro-seconds per hz tick, and the clock 294skew rate. 295.It Li KERN_DOMAINNAME 296Get or set the YP domain name. 297.It Li KERN_FILE 298Return the entire file table. 299The returned data consists of a single 300.Va struct filehead 301followed by an array of 302.Va struct file , 303whose size depends on the current number of such objects in the system. 304.It Li KERN_HOSTID 305Get or set the host id. 306.It Li KERN_HOSTNAME 307Get or set the hostname. 308.It Li KERN_JOB_CONTROL 309Return 1 if job control is available on this system, otherwise 0. 310.It Li KERN_LINK_MAX 311The maximum file link count. 312.It Li KERN_MAXFILES 313The maximum number of open files that may be open in the system. 314.It Li KERN_MAXPARTITIONS 315The maximum number of partitions allowed per disk. 316.It Li KERN_MAXPROC 317The maximum number of simultaneous processes the system will allow. 318.It Li KERN_MAXVNODES 319The maximum number of vnodes available on the system. 320.It Li KERN_MAX_CANON 321The maximum number of bytes in terminal canonical input line. 322.It Li KERN_MAX_INPUT 323The minimum maximum number of bytes for which space is available in 324a terminal input queue. 325.It Li KERN_NAME_MAX 326The maximum number of bytes in a file name. 327.It Li KERN_NGROUPS 328The maximum number of supplemental groups. 329.It Li KERN_NO_TRUNC 330Return 1 if file names longer than KERN_NAME_MAX are truncated. 331.It Li KERN_OSRELEASE 332The system release string. 333.It Li KERN_OSREV 334The system revision string. 335.It Li KERN_OSTYPE 336The system type string. 337.It Li KERN_PATH_MAX 338The maximum number of bytes in a pathname. 339.It Li KERN_PIPE_BUF 340The maximum number of bytes which will be written atomically to a pipe. 341.It Li KERN_POSIX1 342The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 343attempts to comply. 344.It Li KERN_PROC 345Return the entire process table, or a subset of it. 346An array of 347.Va struct kinfo_proc 348structures is returned, 349whose size depends on the current number of such objects in the system. 350The third and fourth level names are as follows: 351.Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent 352.It Pa Third level name Fourth level is: 353.It KERN\_PROC\_ALL None 354.It KERN\_PROC\_PID A process ID 355.It KERN\_PROC\_PGRP A process group 356.It KERN\_PROC\_TTY A tty device 357.It KERN\_PROC\_UID A user ID 358.It KERN\_PROC\_RUID A real user ID 359.El 360.It Li KERN_PROF 361Return profiling information about the kernel. 362If the kernel is not compiled for profiling, 363attempts to retrieve any of the KERN_PROF values will 364fail with EOPNOTSUPP. 365The third level names for the string and integer profiling information 366is detailed below. 367The changeable column shows whether a process with appropriate 368privilege may change the value. 369.Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent 370.It Sy Pa Third level name Type Changeable 371.It GPROF\_STATE integer yes 372.It GPROF\_COUNT u_short[\|] yes 373.It GPROF\_FROMS u_short[\|] yes 374.It GPROF\_TOS struct tostruct yes 375.It GPROF\_GMONPARAM struct gmonparam no 376.El 377.Pp 378The variables are as follows: 379.Bl -tag -width "123456" 380.It Li GPROF_STATE 381Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling 382is running or stopped. 383.It Li GPROF_COUNT 384Array of statistical program counter counts. 385.It Li GPROF_FROMS 386Array indexed by program counter of call-from points. 387.It Li GPROF_TOS 388Array of 389.Va struct tostruct 390describing destination of calls and their counts. 391.It Li GPROF_GMONPARAM 392Structure giving the sizes of the above arrays. 393.El 394.It Li KERN_RAWPARTITION 395The raw partition of a disk (a == 0). 396.It Li KERN_SAVED_IDS 397Returns 1 if saved set-group and saved set-user ID is available. 398.It Li KERN_SECURELVL 399The system security level. 400This level may be raised by processes with appropriate privilege. 401It may only be lowered by process 1. 402.It Li KERN_VDISABLE 403Returns the terminal character disabling value. 404.It Li KERN_VERSION 405The system version string. 406.It Li KERN_VNODE 407Return the entire vnode table. 408Note, the vnode table is not necessarily a consistent snapshot of 409the system. 410The returned data consists of an array whose size depends on the 411current number of such objects in the system. 412Each element of the array contains the kernel address of a vnode 413.Va struct vnode * 414followed by the vnode itself 415.Va struct vnode . 416.El 417.Sh CTL_MACHDEP 418The set of variables defined is architecture dependent. 419Most architectures define at least the following variables. 420.Bl -column "CONSOLE_DEVICEXXX" "integerXXX" -offset indent 421.It Sy Pa Second level name Type Changeable 422.It Li CPU_CONSDEV dev_t no 423.El 424.Sh CTL_NET 425The string and integer information available for the CTL_NET level 426is detailed below. 427The changeable column shows whether a process with appropriate 428privilege may change the value. 429.Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent 430.It Sy Pa Second level name Type Changeable 431.It PF\_ROUTE routing messages no 432.It PF\_INET internet values yes 433.El 434.Pp 435.Bl -tag -width "123456" 436.It Li PF_ROUTE 437Return the entire routing table or a subset of it. 438The data is returned as a sequence of routing messages (see 439.Xr route 4 440for the header file, format and meaning). 441The length of each message is contained in the message header. 442.Pp 443The third level name is a protocol number, which is currently always 0. 444The fourth level name is an address family, which may be set to 0 to 445select all address families. 446The fifth and sixth level names are as follows: 447.Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent 448.It Pa Fifth level name Sixth level is: 449.It NET\_RT\_FLAGS rtflags 450.It NET\_RT\_DUMP None 451.It NET\_RT\_IFLIST None 452.El 453.It Li PF_INET 454Get or set various global information about the internet protocols. 455The third level name is the protocol. 456The fourth level name is the variable name. 457The currently defined protocols and names are: 458.Bl -column "Protocol name" "Variable nameXX" "integer" "yes" -offset indent 459.It Pa Protocol name Variable name Type Changeable 460.It ip forwarding integer yes 461.It ip redirect integer yes 462.It ip ttl integer yes 463.It ip forwsrcrt integer yes 464.It ip directed-broadcast integer yes 465.It icmp maskrepl integer yes 466.It tcp rfc1323 integer yes 467.It udp checksum integer yes 468.El 469.Pp 470The variables are as follows: 471.Bl -tag -width "123456" 472.It Li ip.forwarding 473Returns 1 when IP forwarding is enabled for the host, 474meaning that the host is acting as a router. 475.It Li ip.redirect 476Returns 1 when ICMP redirects may be sent by the host. 477This option is ignored unless the host is routing IP packets, 478and should normally be enabled on all systems. 479.It Li ip.ttl 480The maximum time-to-live (hop count) value for an IP packet sourced by 481the system. 482This value applies to normal transport protocols, not to ICMP. 483.It Li ip.forwsrcrt 484Returns 1 when forwarding of source-routed packets is enabled for 485the host. This value may only be changed if the kernel security 486level is less than 1. 487.It Li ip.directed-broadcast 488Returns 1 if directed broadcast behavior is enabled for the host. 489.It Li icmp.maskrepl 490Returns 1 if ICMP network mask requests are to be answered. 491.It Li tcp.rfc1323 492Returns 1 if RFC1323 extensions to TCP are enabled. 493.It Li udp.checksum 494Returns 1 when UDP checksums are being computed and checked. 495Disabling UDP checksums is strongly discouraged. 496.El 497.Sh CTL_USER 498The string and integer information available for the CTL_USER level 499is detailed below. 500The changeable column shows whether a process with appropriate 501privilege may change the value. 502.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent 503.It Sy Pa Second level name Type Changeable 504.It USER\_BC\_BASE\_MAX integer no 505.It USER\_BC\_DIM\_MAX integer no 506.It USER\_BC\_SCALE\_MAX integer no 507.It USER\_BC\_STRING\_MAX integer no 508.It USER\_COLL\_WEIGHTS\_MAX integer no 509.It USER\_CS\_PATH string no 510.It USER\_EXPR\_NEST\_MAX integer no 511.It USER\_LINE\_MAX integer no 512.It USER\_POSIX2\_CHAR\_TERM integer no 513.It USER\_POSIX2\_C\_BIND integer no 514.It USER\_POSIX2\_C\_DEV integer no 515.It USER\_POSIX2\_FORT\_DEV integer no 516.It USER\_POSIX2\_FORT\_RUN integer no 517.It USER\_POSIX2\_LOCALEDEF integer no 518.It USER\_POSIX2\_SW\_DEV integer no 519.It USER\_POSIX2\_UPE integer no 520.It USER\_POSIX2\_VERSION integer no 521.It USER\_RE\_DUP\_MAX integer no 522.It USER\_STREAM\_MAX integer no 523.It USER\_TZNAME\_MAX integer no 524.El 525.Bl -tag -width "123456" 526.Pp 527.It Li USER_BC_BASE_MAX 528The maximum ibase/obase values in the 529.Xr bc 1 530utility. 531.It Li USER_BC_DIM_MAX 532The maximum array size in the 533.Xr bc 1 534utility. 535.It Li USER_BC_SCALE_MAX 536The maximum scale value in the 537.Xr bc 1 538utility. 539.It Li USER_BC_STRING_MAX 540The maximum string length in the 541.Xr bc 1 542utility. 543.It Li USER_COLL_WEIGHTS_MAX 544The maximum number of weights that can be assigned to any entry of 545the LC_COLLATE order keyword in the locale definition file. 546.It Li USER_CS_PATH 547Return a value for the 548.Ev PATH 549environment variable that finds all the standard utilities. 550.It Li USER_EXPR_NEST_MAX 551The maximum number of expressions that can be nested within 552parenthesis by the 553.Xr expr 1 554utility. 555.It Li USER_LINE_MAX 556The maximum length in bytes of a text-processing utility's input 557line. 558.It Li USER_POSIX2_CHAR_TERM 559Return 1 if the system supports at least one terminal type capable of 560all operations described in POSIX 1003.2, otherwise 0. 561.It Li USER_POSIX2_C_BIND 562Return 1 if the system's C-language development facilities support the 563C-Language Bindings Option, otherwise 0. 564.It Li USER_POSIX2_C_DEV 565Return 1 if the system supports the C-Language Development Utilities Option, 566otherwise 0. 567.It Li USER_POSIX2_FORT_DEV 568Return 1 if the system supports the FORTRAN Development Utilities Option, 569otherwise 0. 570.It Li USER_POSIX2_FORT_RUN 571Return 1 if the system supports the FORTRAN Runtime Utilities Option, 572otherwise 0. 573.It Li USER_POSIX2_LOCALEDEF 574Return 1 if the system supports the creation of locales, otherwise 0. 575.It Li USER_POSIX2_SW_DEV 576Return 1 if the system supports the Software Development Utilities Option, 577otherwise 0. 578.It Li USER_POSIX2_UPE 579Return 1 if the system supports the User Portability Utilities Option, 580otherwise 0. 581.It Li USER_POSIX2_VERSION 582The version of POSIX 1003.2 with which the system attempts to comply. 583.It Li USER_RE_DUP_MAX 584The maximum number of repeated occurrences of a regular expression 585permitted when using interval notation. 586.It Li USER_STREAM_MAX 587The minimum maximum number of streams that a process may have open 588at any one time. 589.It Li USER_TZNAME_MAX 590The minimum maximum number of types supported for the name of a 591timezone. 592.El 593.Sh CTL_VM 594The string and integer information available for the CTL_VM level 595is detailed below. 596The changeable column shows whether a process with appropriate 597privilege may change the value. 598.Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent 599.It Sy Pa Second level name Type Changeable 600.It VM\_LOADAVG struct loadavg no 601.It VM\_METER struct vmtotal no 602.El 603.Pp 604.Bl -tag -width "123456" 605.It Li VM_LOADAVG 606Return the load average history. 607The returned data consists of a 608.Va struct loadavg . 609.It Li VM_METER 610Return the system wide virtual memory statistics. 611The returned data consists of a 612.Va struct vmtotal . 613.El 614.Sh RETURN VALUES 615If the call to 616.Nm sysctl 617is successful, 0 is returned. 618Otherwise \-1 is returned and 619.Va errno 620is set appropriately. 621.Sh ERRORS 622The following errors may be reported: 623.Bl -tag -width Er 624.It Bq Er EFAULT 625The buffer 626.Fa name , 627.Fa oldp , 628.Fa newp , 629or length pointer 630.Fa oldlenp 631contains an invalid address. 632.It Bq Er EINVAL 633The 634.Fa name 635array is less than two or greater than CTL_MAXNAME. 636.It Bq Er EINVAL 637A non-null 638.Fa newp 639is given and its specified length in 640.Fa newlen 641is too large or too small. 642.It Bq Er ENOMEM 643The length pointed to by 644.Fa oldlenp 645is too short to hold the requested value. 646.It Bq Er ENOTDIR 647The 648.Fa name 649array specifies an intermediate rather than terminal name. 650.It Bq Er EOPNOTSUPP 651The 652.Fa name 653array specifies a value that is unknown. 654.It Bq Er EPERM 655An attempt is made to set a read-only value. 656.It Bq Er EPERM 657A process without appropriate privilege attempts to set a value. 658.It Bq Er EPERM 659An attempt to change a value protected by the current kernel security 660level is made. 661.El 662.Sh FILES 663.Bl -tag -width <netinet/icmpXvar.h> -compact 664.It Pa <sys/sysctl.h> 665definitions for top level identifiers, second level kernel and hardware 666identifiers, and user level identifiers 667.It Pa <sys/socket.h> 668definitions for second level network identifiers 669.It Pa <sys/gmon.h> 670definitions for third level profiling identifiers 671.It Pa <vm/vm_param.h> 672definitions for second level virtual memory identifiers 673.It Pa <netinet/in.h> 674definitions for third level Internet identifiers and 675fourth level IP identifiers 676.It Pa <netinet/icmp_var.h> 677definitions for fourth level ICMP identifiers 678.It Pa <netinet/tcp_var.h> 679definitions for fourth level TCP identifiers 680.It Pa <netinet/udp_var.h> 681definitions for fourth level UDP identifiers 682.El 683.Sh SEE ALSO 684.Xr sysctl 8 685.Sh HISTORY 686The 687.Nm sysctl 688function first appeared in 4.4BSD. 689