1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95 33.\" 34.Dd "May 9, 1995" 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 80and after a call that returns with the error code ENOMEM. 81If the amount of data available is greater 82than the size of the buffer supplied, 83the call supplies as much data as fits in the buffer provided 84and returns with the error code ENOMEM. 85If the old value is not desired, 86.Fa oldp 87and 88.Fa oldlenp 89should be set to NULL. 90.Pp 91The size of the available data can be determined by calling 92.Fn sysctl 93with a NULL parameter for 94.Fa oldp . 95The size of the available data will be returned in the location pointed to by 96.Fa oldlenp . 97For some operations, the amount of space may change often. 98For these operations, 99the system attempts to round up so that the returned size is 100large enough for a call to return the data shortly thereafter. 101.Pp 102To set a new value, 103.Fa newp 104is set to point to a buffer of length 105.Fa newlen 106from which the requested value is to be taken. 107If a new value is not to be set, 108.Fa newp 109should be set to NULL and 110.Fa newlen 111set to 0. 112.Pp 113The top level names are defined with a CTL_ prefix in 114.Pa <sys/sysctl.h> , 115and are as follows. 116The next and subsequent levels down are found in the include files 117listed here, and described in separate sections below. 118.Pp 119.Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent 120.It Sy Pa Name Next level names Description 121.It CTL\_DEBUG sys/sysctl.h Debugging 122.It CTL\_VFS sys/mount.h Filesystem 123.It CTL\_HW sys/sysctl.h Generic CPU, I/O 124.It CTL\_KERN sys/sysctl.h High kernel limits 125.It CTL\_MACHDEP sys/sysctl.h Machine dependent 126.It CTL\_NET sys/socket.h Networking 127.It CTL\_USER sys/sysctl.h User-level 128.It CTL\_VM vm/vm_param.h Virtual memory 129.El 130.Pp 131For example, the following retrieves the maximum number of processes allowed 132in the system: 133.Pp 134.Bd -literal -offset indent -compact 135int mib[2], maxproc; 136size_t len; 137 138mib[0] = CTL_KERN; 139mib[1] = KERN_MAXPROC; 140len = sizeof(maxproc); 141sysctl(mib, 2, &maxproc, &len, NULL, 0); 142.Ed 143.Pp 144To retrieve the standard search path for the system utilities: 145.Pp 146.Bd -literal -offset indent -compact 147int mib[2]; 148size_t len; 149char *p; 150 151mib[0] = CTL_USER; 152mib[1] = USER_CS_PATH; 153sysctl(mib, 2, NULL, &len, NULL, 0); 154p = malloc(len); 155sysctl(mib, 2, p, &len, NULL, 0); 156.Ed 157.Sh CTL_DEBUG 158The debugging variables vary from system to system. 159A debugging variable may be added or deleted without need to recompile 160.Fn sysctl 161to know about it. 162Each time it runs, 163.Fn sysctl 164gets the list of debugging variables from the kernel and 165displays their current values. 166The system defines twenty 167.Ns ( Va struct ctldebug ) 168variables named 169.Nm debug0 170through 171.Nm debug19 . 172They are declared as separate variables so that they can be 173individually initialized at the location of their associated variable. 174The loader prevents multiple use of the same variable by issuing errors 175if a variable is initialized in more than one place. 176For example, to export the variable 177.Nm dospecialcheck 178as a debugging variable, the following declaration would be used: 179.Bd -literal -offset indent -compact 180int dospecialcheck = 1; 181struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; 182.Ed 183.Sh CTL_VFS 184A distinguished second level name, VFS_GENERIC, 185is used to get general information about all filesystems. 186One of its third level identifiers is VFS_MAXTYPENUM 187that gives the highest valid filesystem type number. 188Its other third level identifier is VFS_CONF that 189returns configuration information about the filesystem 190type given as a fourth level identifier (see 191.Xr getvfsbyname 3 192as an example of its use). 193The remaining second level identifiers are the 194filesystem type number returned by a 195.Xr statfs 2 196call or from VFS_CONF. 197The third level identifiers available for each filesystem 198are given in the header file that defines the mount 199argument structure for that filesystem. 200.Sh CTL_HW 201The string and integer information available for the CTL_HW level 202is detailed below. 203The changeable column shows whether a process with appropriate 204privilege may change the value. 205.Bl -column "Second level nameXXXXXX" integerXXX -offset indent 206.It Sy Pa Second level name Type Changeable 207.It HW\_MACHINE string no 208.It HW\_MODEL string no 209.It HW\_NCPU integer no 210.It HW\_BYTEORDER integer no 211.It HW\_PHYSMEM integer no 212.It HW\_USERMEM integer no 213.It HW\_PAGESIZE integer no 214.It HW\_FLOATINGPOINT integer no 215.\".It HW\_DISKNAMES integer no 216.\".It HW\_DISKSTATS integer no 217.El 218.Pp 219.Bl -tag -width "123456" 220.It Li HW_MACHINE 221The machine class. 222.It Li HW_MODEL 223The machine model 224.It Li HW_NCPU 225The number of cpus. 226.ne 1i 227.It Li HW_BYTEORDER 228The byteorder (4,321, or 1,234). 229.It Li HW_PHYSMEM 230The bytes of physical memory. 231.It Li HW_USERMEM 232The bytes of non-kernel memory. 233.It Li HW_PAGESIZE 234The software page size. 235.It Li HW_FLOATINGPOINT 236Nonzero if the floating point support is in hardware. 237.\".It Fa HW_DISKNAMES 238.\".It Fa HW_DISKSTATS 239.El 240.Sh CTL_KERN 241The string and integer information available for the CTL_KERN level 242is detailed below. 243The changeable column shows whether a process with appropriate 244privilege may change the value. 245The types of data currently available are process information, 246system vnodes, the open file entries, routing table entries, 247virtual memory statistics, load average history, and clock rate 248information. 249.Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent 250.It Sy Pa Second level name Type Changeable 251.It KERN\_ARGMAX integer no 252.It KERN\_BOOTFILE string yes 253.It KERN\_BOOTTIME struct timeval no 254.It KERN\_CLOCKRATE struct clockinfo no 255.It KERN\_FILE struct file no 256.It KERN\_HOSTID integer yes 257.It KERN\_HOSTNAME string yes 258.It KERN\_JOB\_CONTROL integer no 259.It KERN\_MAXFILES integer yes 260.It KERN\_MAXFILESPERPROC integer yes 261.It KERN\_MAXPROC integer yes 262.It KERN\_MAXPROCPERUID integer yes 263.It KERN\_MAXVNODES integer yes 264.It KERN\_NGROUPS integer no 265.It KERN\_NISDOMAINNAME string yes 266.It KERN\_OSRELDATE integer no 267.It KERN\_OSRELEASE string no 268.It KERN\_OSREV integer no 269.It KERN\_OSTYPE string no 270.It KERN\_POSIX1 integer no 271.It KERN\_PROC struct proc no 272.It KERN\_PROF node not applicable 273.It KERN\_SAVED\_IDS integer no 274.It KERN\_SECURELVL integer raise only 275.It KERN\_UPDATEINTERVAL integer no 276.It KERN\_VERSION string no 277.It KERN\_VNODE struct vnode no 278.El 279.ne 1i 280.Pp 281.Bl -tag -width "123456" 282.It Li KERN_ARGMAX 283The maximum bytes of argument to 284.Xr execve 2 . 285.It Li KERN_BOOTFILE 286The full pathname of the file from which the kernel was loaded. 287.It Li KERN_BOOTTIME 288A 289.Va struct timeval 290structure is returned. 291This structure contains the time that the system was booted. 292.It Li KERN_CLOCKRATE 293A 294.Va struct clockinfo 295structure is returned. 296This structure contains the clock, statistics clock and profiling clock 297frequencies, and the number of micro-seconds per hz tick. 298.It Li KERN_FILE 299Return the entire file table. 300The returned data consists of a single 301.Va struct filehead 302followed by an array of 303.Va struct file , 304whose size depends on the current number of such objects in the system. 305.It Li KERN_HOSTID 306Get or set the host id. 307.It Li KERN_HOSTNAME 308Get or set the hostname. 309.It Li KERN_JOB_CONTROL 310Return 1 if job control is available on this system, otherwise 0. 311.It Li KERN_MAXFILES 312The maximum number of files that may be open in the system. 313.It Li KERN_MAXFILESPERPROC 314The maximum number of files that may be open for a single process. 315This limit only applies to processes with an effective uid of nonzero 316at the time of the open request. 317Files that have already been opened are not affected if the limit 318or the effective uid is changed. 319.It Li KERN_MAXPROC 320The maximum number of concurrent processes the system will allow. 321.It Li KERN_MAXPROCPERUID 322The maximum number of concurrent processes the system will allow 323for a single effective uid. 324This limit only applies to processes with an effective uid of nonzero 325at the time of a fork request. 326Processes that have already been started are not affected if the limit 327is changed. 328.It Li KERN_MAXVNODES 329The maximum number of vnodes available on the system. 330.It Li KERN_NGROUPS 331The maximum number of supplemental groups. 332.It Li KERN_NISDOMAINNAME 333The name of the current YP/NIS domain. 334.It Li KERN_OSRELDATE 335The system release date in YYYYMM format 336(January 1996 is encoded as 199601). 337.It Li KERN_OSRELEASE 338The system release string. 339.It Li KERN_OSREV 340The system revision string. 341.It Li KERN_OSTYPE 342The system type string. 343.It Li KERN_POSIX1 344The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 345attempts to comply. 346.It Li KERN_PROC 347Return the entire process table, or a subset of it. 348An array of 349.Va struct kinfo_proc 350structures is returned, 351whose size depends on the current number of such objects in the system. 352The third and fourth level names are as follows: 353.Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent 354.It Pa Third level name Fourth level is: 355.It KERN\_PROC\_ALL None 356.It KERN\_PROC\_PID A process ID 357.It KERN\_PROC\_PGRP A process group 358.It KERN\_PROC\_TTY A tty device 359.It KERN\_PROC\_UID A user ID 360.It KERN\_PROC\_RUID A real user ID 361.El 362.It Li KERN_PROF 363Return profiling information about the kernel. 364If the kernel is not compiled for profiling, 365attempts to retrieve any of the KERN_PROF values will 366fail with EOPNOTSUPP. 367The third level names for the string and integer profiling information 368is detailed below. 369The changeable column shows whether a process with appropriate 370privilege may change the value. 371.Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent 372.It Sy Pa Third level name Type Changeable 373.It GPROF\_STATE integer yes 374.It GPROF\_COUNT u_short[\|] yes 375.It GPROF\_FROMS u_short[\|] yes 376.It GPROF\_TOS struct tostruct yes 377.It GPROF\_GMONPARAM struct gmonparam no 378.El 379.Pp 380The variables are as follows: 381.Bl -tag -width "123456" 382.It Li GPROF_STATE 383Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling 384is running or stopped. 385.It Li GPROF_COUNT 386Array of statistical program counter counts. 387.It Li GPROF_FROMS 388Array indexed by program counter of call-from points. 389.It Li GPROF_TOS 390Array of 391.Va struct tostruct 392describing destination of calls and their counts. 393.It Li GPROF_GMONPARAM 394Structure giving the sizes of the above arrays. 395.El 396.ne 1i 397.It Li KERN_SAVED_IDS 398Returns 1 if saved set-group and saved set-user ID is available. 399.It Li KERN_SECURELVL 400The system security level. 401This level may be raised by processes with appropriate privilege. 402It may only be lowered by process 1. 403.It Li KERN_VERSION 404The system version string. 405.It Li KERN_VNODE 406Return the entire vnode table. 407Note, the vnode table is not necessarily a consistent snapshot of 408the system. 409The returned data consists of an array whose size depends on the 410current number of such objects in the system. 411Each element of the array contains the kernel address of a vnode 412.Va struct vnode * 413followed by the vnode itself 414.Va struct vnode . 415.It Li KERN_UPDATEINTERVAL 416The interval between 417.Xr sync 2 418calls in the 419.Xr update 4 420process. 421.El 422.Sh CTL_MACHDEP 423The set of variables defined is architecture dependent. 424The following variables are defined for the i386 architecture. 425.Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent 426.It Sy Pa Second level name Type Changeable 427.It Li CPU_CONSDEV dev_t no 428.It Li CPU_ADJKERNTZ int yes 429.It Li CPU_DISRTCSET int yes 430.It Li CPU_BOOTINFO struct bootinfo no 431.It Li CPU_WALLCLOCK int yes 432.El 433.Sh CTL_NET 434The string and integer information available for the CTL_NET level 435is detailed below. 436The changeable column shows whether a process with appropriate 437privilege may change the value. 438.Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent 439.It Sy Pa Second level name Type Changeable 440.It PF\_ROUTE routing messages no 441.It PF\_INET internet values yes 442.El 443.Pp 444.Bl -tag -width "123456" 445.It Li PF_ROUTE 446Return the entire routing table or a subset of it. 447The data is returned as a sequence of routing messages (see 448.Xr route 4 449for the header file, format and meaning). 450The length of each message is contained in the message header. 451.Pp 452The third level name is a protocol number, which is currently always 0. 453The fourth level name is an address family, which may be set to 0 to 454select all address families. 455The fifth and sixth level names are as follows: 456.Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent 457.It Pa Fifth level name Sixth level is: 458.It NET\_RT\_FLAGS rtflags 459.It NET\_RT\_DUMP None 460.It NET\_RT\_IFLIST None 461.El 462.It Li PF_INET 463Get or set various global information about the internet protocols. 464The third level name is the protocol. 465The fourth level name is the variable name. 466The currently defined protocols and names are: 467.ne 1i 468.Bl -column "Protocol nameXXXXXX" "Variable nameXXX" "integerXXX" -offset indent 469.It Pa Protocol name Variable name Type Changeable 470.It ip forwarding integer yes 471.It ip redirect integer yes 472.It ip ttl integer yes 473.It icmp maskrepl integer yes 474.It udp checksum integer yes 475.El 476.Pp 477The variables are as follows: 478.Bl -tag -width "123456" 479.It Li ip.forwarding 480Returns 1 when IP forwarding is enabled for the host, 481meaning that the host is acting as a router. 482.It Li ip.redirect 483Returns 1 when ICMP redirects may be sent by the host. 484This option is ignored unless the host is routing IP packets, 485and should normally be enabled on all systems. 486.It Li ip.ttl 487The maximum time-to-live (hop count) value for an IP packet sourced by 488the system. 489This value applies to normal transport protocols, not to ICMP. 490.It Li icmp.maskrepl 491Returns 1 if ICMP network mask requests are to be answered. 492.It Li udp.checksum 493Returns 1 when UDP checksums are being computed and checked. 494Disabling UDP checksums is strongly discouraged. 495.El 496.Sh CTL_USER 497The string and integer information available for the CTL_USER level 498is detailed below. 499The changeable column shows whether a process with appropriate 500privilege may change the value. 501.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent 502.It Sy Pa Second level name Type Changeable 503.It USER\_BC\_BASE\_MAX integer no 504.It USER\_BC\_DIM\_MAX integer no 505.It USER\_BC\_SCALE\_MAX integer no 506.It USER\_BC\_STRING\_MAX integer no 507.It USER\_COLL\_WEIGHTS\_MAX integer no 508.It USER\_CS\_PATH string no 509.It USER\_EXPR\_NEST\_MAX integer no 510.It USER\_LINE\_MAX integer no 511.It USER\_POSIX2\_CHAR\_TERM integer no 512.It USER\_POSIX2\_C\_BIND integer no 513.It USER\_POSIX2\_C\_DEV integer no 514.It USER\_POSIX2\_FORT\_DEV integer no 515.It USER\_POSIX2\_FORT\_RUN integer no 516.It USER\_POSIX2\_LOCALEDEF integer no 517.It USER\_POSIX2\_SW\_DEV integer no 518.It USER\_POSIX2\_UPE integer no 519.It USER\_POSIX2\_VERSION integer no 520.It USER\_RE\_DUP\_MAX integer no 521.It USER\_STREAM\_MAX integer no 522.It USER\_TZNAME\_MAX integer no 523.El 524.Bl -tag -width "123456" 525.Pp 526.It Li USER_BC_BASE_MAX 527The maximum ibase/obase values in the 528.Xr bc 1 529utility. 530.It Li USER_BC_DIM_MAX 531The maximum array size in the 532.Xr bc 1 533utility. 534.It Li USER_BC_SCALE_MAX 535The maximum scale value in the 536.Xr bc 1 537utility. 538.It Li USER_BC_STRING_MAX 539The maximum string length in the 540.Xr bc 1 541utility. 542.It Li USER_COLL_WEIGHTS_MAX 543The maximum number of weights that can be assigned to any entry of 544the LC_COLLATE order keyword in the locale definition file. 545.It Li USER_CS_PATH 546Return a value for the 547.Ev PATH 548environment variable that finds all the standard utilities. 549.It Li USER_EXPR_NEST_MAX 550The maximum number of expressions that can be nested within 551parenthesis by the 552.Xr expr 1 553utility. 554.It Li USER_LINE_MAX 555The maximum length in bytes of a text-processing utility's input 556line. 557.It Li USER_POSIX2_CHAR_TERM 558Return 1 if the system supports at least one terminal type capable of 559all operations described in POSIX 1003.2, otherwise 0. 560.It Li USER_POSIX2_C_BIND 561Return 1 if the system's C-language development facilities support the 562C-Language Bindings Option, otherwise 0. 563.It Li USER_POSIX2_C_DEV 564Return 1 if the system supports the C-Language Development Utilities Option, 565otherwise 0. 566.It Li USER_POSIX2_FORT_DEV 567Return 1 if the system supports the FORTRAN Development Utilities Option, 568otherwise 0. 569.It Li USER_POSIX2_FORT_RUN 570Return 1 if the system supports the FORTRAN Runtime Utilities Option, 571otherwise 0. 572.It Li USER_POSIX2_LOCALEDEF 573Return 1 if the system supports the creation of locales, otherwise 0. 574.It Li USER_POSIX2_SW_DEV 575Return 1 if the system supports the Software Development Utilities Option, 576otherwise 0. 577.It Li USER_POSIX2_UPE 578Return 1 if the system supports the User Portability Utilities Option, 579otherwise 0. 580.It Li USER_POSIX2_VERSION 581The version of POSIX 1003.2 with which the system attempts to comply. 582.It Li USER_RE_DUP_MAX 583The maximum number of repeated occurrences of a regular expression 584permitted when using interval notation. 585.ne 1i 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.Fn sysctl 617is successful, the number of bytes copied out 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.El 659.Sh FILES 660.Bl -tag -width <netinet/icmpXvar.h> -compact 661.It Pa <sys/sysctl.h> 662definitions for top level identifiers, second level kernel and hardware 663identifiers, and user level identifiers 664.It Pa <sys/socket.h> 665definitions for second level network identifiers 666.It Pa <sys/gmon.h> 667definitions for third level profiling identifiers 668.It Pa <vm/vm_param.h> 669definitions for second level virtual memory identifiers 670.It Pa <netinet/in.h> 671definitions for third level Internet identifiers and 672fourth level IP identifiers 673.It Pa <netinet/icmp_var.h> 674definitions for fourth level ICMP identifiers 675.It Pa <netinet/udp_var.h> 676definitions for fourth level UDP identifiers 677.El 678.Sh SEE ALSO 679.Xr sysctl 8 680.Sh HISTORY 681The 682.Fn sysctl 683function first appeared in 684.Bx 4.4 . 685