.\" $OpenBSD: sysctl.3,v 1.28 1999/07/26 12:50:54 aaron Exp $ .\" .\" Copyright (c) 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .Dd June 4, 1993 .Dt SYSCTL 3 .Os .Sh NAME .Nm sysctl .Nd get or set system information .Sh SYNOPSIS .Fd #include .Fd #include .Ft int .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen" .Sh DESCRIPTION The .Fn sysctl function retrieves system information and allows processes with appropriate privileges to set system information. The information available from .Fn sysctl consists of integers, strings, and tables. Information may be retrieved and set from the command interface using the .Xr sysctl 8 utility. .Pp Unless explicitly noted below, .Fn sysctl returns a consistent snapshot of the data requested. Consistency is obtained by locking the destination buffer into memory so that the data may be copied out without blocking. Calls to .Fn sysctl are serialized to avoid deadlock. .Pp The state is described using a .Dq Management Information Base (MIB) style name, listed in .Fa name , which is a .Fa namelen length array of integers. .Pp The information is copied into the buffer specified by .Fa oldp . The size of the buffer is given by the location specified by .Fa oldlenp before the call, and that location gives the amount of data copied after a successful call. If the amount of data available is greater than the size of the buffer supplied, the call supplies as much data as fits in the buffer provided and returns with the error code .Er ENOMEM . If the old value is not desired, .Fa oldp and .Fa oldlenp should be set to .Dv NULL . .Pp The size of the available data can be determined by calling .Fn sysctl with a .Dv NULL parameter for .Fa oldp . The size of the available data will be returned in the location pointed to by .Fa oldlenp . For some operations, the amount of space may change often. For these operations, the system attempts to round up so that the returned size is large enough for a call to return the data shortly thereafter. .Pp To set a new value, .Fa newp is set to point to a buffer of length .Fa newlen from which the requested value is to be taken. If a new value is not to be set, .Fa newp should be set to .Dv NULL and .Fa newlen set to 0. .Pp The top level names are defined with a .Dv CTL_ prefix in .Aq Pa sys/sysctl.h , and are as follows. The next and subsequent levels down are found in the include files listed here, and described in separate sections below. .Pp .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent .It Sy Name Next level names Description .It Dv CTL_DEBUG No " sys/sysctl.h Debugging" .It Dv CTL_FS No " sys/sysctl.h File system" .It Dv CTL_HW No " sys/sysctl.h Generic CPU, I/O" .It Dv CTL_KERN No " sys/sysctl.h High kernel limits" .It Dv CTL_MACHDEP No " sys/sysctl.h Machine dependent" .It Dv CTL_NET No " sys/socket.h Networking" .It Dv CTL_USER No " sys/sysctl.h User-level" .It Dv CTL_VM No " vm/vm_param.h Virtual memory" .El .Pp For example, the following retrieves the maximum number of processes allowed in the system: .Pp .Bd -literal -offset indent -compact int mib[2], maxproc; size_t len; mib[0] = CTL_KERN; mib[1] = KERN_MAXPROC; len = sizeof(maxproc); sysctl(mib, 2, &maxproc, &len, NULL, 0); .Ed .Pp To retrieve the standard search path for the system utilities: .Pp .Bd -literal -offset indent -compact int mib[2]; size_t len; char *p; mib[0] = CTL_USER; mib[1] = USER_CS_PATH; sysctl(mib, 2, NULL, &len, NULL, 0); p = malloc(len); sysctl(mib, 2, p, &len, NULL, 0); .Ed .Ss CTL_DEBUG The debugging variables vary from system to system. A debugging variable may be added or deleted without need to recompile .Fn sysctl to know about it. Each time it runs, .Fn sysctl gets the list of debugging variables from the kernel and displays their current values. The system defines twenty .Li struct ctldebug variables named .Va debug0 through .Va debug19 . They are declared as separate variables so that they can be individually initialized at the location of their associated variable. The loader prevents multiple use of the same variable by issuing errors if a variable is initialized in more than one place. For example, to export the variable .Va dospecialcheck as a debugging variable, the following declaration would be used: .Pp .Bd -literal -offset indent -compact int dospecialcheck = 1; struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; .Ed .Ss CTL_FS There are currently no second level names for the file system. .Ss CTL_HW The string and integer information available for the .Dv CTL_HW level is detailed below. The changeable column shows whether a process with appropriate privileges may change the value. .Bl -column "Second level nameXXXXXX" integerXXX -offset indent .It Sy Second level name Type Changeable .It Dv HW_MACHINE No " string no" .It Dv HW_MODEL No " string no" .It Dv HW_NCPU No " integer no" .It Dv HW_BYTEORDER No " integer no" .It Dv HW_PHYSMEM No " integer no" .It Dv HW_USERMEM No " integer no" .It Dv HW_PAGESIZE No " integer no" .\".It Dv HW_DISKNAMES No " integer no" .\".It Dv HW_DISKSTATS No " integer no" .El .Pp .Bl -tag -width "123456" .It Dv HW_MACHINE The machine class. .It Dv HW_MODEL The machine model .It Dv HW_NCPU The number of CPUs. .It Dv HW_BYTEORDER The byteorder (4,321 or 1,234). .It Dv HW_PHYSMEM The bytes of physical memory. .It Dv HW_USERMEM The bytes of non-kernel memory. .It Dv HW_PAGESIZE The software page size. .\".It Dv HW_DISKNAMES .\".It Dv HW_DISKSTATS .El .Ss CTL_KERN The string and integer information available for the .Dv CTL_KERN level is detailed below. The changeable column shows whether a process with appropriate privileges may change the value. The types of data currently available are process information, system vnodes, the open file entries, routing table entries, virtual memory statistics, load average history, and clock rate information. .Bl -column "KERNXCHOWNXRESTRICTEDXXX" "struct clockrateXXX" -offset indent .It Sy Second level name Type Changeable .It Dv KERN_ARGMAX No " integer no" .It Dv KERN_ARND No " integer no" .It Dv KERN_BOOTTIME No " struct timeval no" .It Dv KERN_CHOWN_RESTRICTED No " integer no" .It Dv KERN_CLOCKRATE No " struct clockinfo no" .It Dv KERN_DOMAINNAME No " string yes" .It Dv KERN_FILE No " struct file no" .It Dv KERN_FSYNC No " integer no" .It Dv KERN_HOSTID No " integer yes" .It Dv KERN_HOSTNAME No " string yes" .It Dv KERN_JOB_CONTROL No " integer no" .It Dv KERN_LINK_MAX No " integer no" .It Dv KERN_MAXFILES No " integer yes" .It Dv KERN_MAXPARTITIONS No " integer no" .It Dv KERN_MAXPROC No " integer yes" .It Dv KERN_MAXVNODES No " integer yes" .It Dv KERN_MAX_CANON No " integer no" .It Dv KERN_MAX_INPUT No " integer no" .It Dv KERN_NAME_MAX No " integer no" .It Dv KERN_NGROUPS No " integer no" .It Dv KERN_NO_TRUNC No " integer no" .It Dv KERN_NOSUIDCOREDUMP No " integer yes" .It Dv KERN_OSRELEASE No " string no" .It Dv KERN_OSREV No " integer no" .It Dv KERN_OSTYPE No " string no" .It Dv KERN_PATH_MAX No " integer no" .It Dv KERN_PIPE_BUF No " integer no" .It Dv KERN_POSIX1 No " integer no" .It Dv KERN_PROC No " struct proc no" .It Dv KERN_PROF No " node not applicable" .It Dv KERN_RAWPARTITION No " integer no" .It Dv KERN_RND No " struct rndstats no" .It Dv KERN_SAVED_IDS No " integer no" .It Dv KERN_SECURELVL No " integer raise only" .It Dv KERN_SYSVMSG No " integer no" .It Dv KERN_SYSVSEM No " integer no" .It Dv KERN_SYSVSHM No " integer no" .It Dv KERN_VDISABLE No " integer no" .It Dv KERN_VERSION No " string no" .It Dv KERN_VNODE No " struct vnode no" .El .Pp .Bl -tag -width "123456" .It Dv KERN_ARGMAX The maximum bytes of argument to .Xr exec 2 . .It Dv KERN_ARND Returns a random integer from the kernel .Fn arc4random function. This can be useful if .Pa /dev/arandom is not available (see .Xr random 4 ) . .It Dv KERN_BOOTTIME A .Li struct timeval structure is returned. This structure contains the time that the system was booted. .It Dv KERN_CHOWN_RESTRICTED Return 1 if appropriate privileges are required for the .Xr chown 2 system call, otherwise 0. .It Dv KERN_CLOCKRATE A .Li struct clockinfo structure is returned. This structure contains the clock, statistics clock and profiling clock frequencies, the number of micro-seconds per hz tick, and the clock skew rate. .It Dv KERN_DOMAINNAME Get or set the YP domain name. .It Dv KERN_FILE Return the entire file table. The returned data consists of a single .Li struct filehead followed by an array of .Li struct file , whose size depends on the current number of such objects in the system. .It Dv KERN_FSYNC Return 1 if the File Synchronisation Option is available on this system, otherwise 0. .It Dv KERN_HOSTID Get or set the host ID. .It Dv KERN_HOSTNAME Get or set the hostname. .It Dv KERN_JOB_CONTROL Return 1 if job control is available on this system, otherwise 0. .It Dv KERN_LINK_MAX The maximum file link count. .It Dv KERN_MAXFILES The maximum number of open files that may be open in the system. .It Dv KERN_MAXPARTITIONS The maximum number of partitions allowed per disk. .It Dv KERN_MAXPROC The maximum number of simultaneous processes the system will allow. .It Dv KERN_MAXVNODES The maximum number of vnodes available on the system. .It Dv KERN_MAX_CANON The maximum number of bytes in terminal canonical input line. .It Dv KERN_MAX_INPUT The minimum maximum number of bytes for which space is available in a terminal input queue. .It Dv KERN_NAME_MAX The maximum number of bytes in a file name. .It Dv KERN_NGROUPS The maximum number of supplemental groups. .It Dv KERN_NO_TRUNC Return 1 if file names longer than .Dv KERN_NAME_MAX are truncated. .It Dv KERN_NOSUIDCOREDUMP Programs with their set-user-ID bit set will not dump core when this is set. .It Dv KERN_OSRELEASE The system release string. .It Dv KERN_OSREV The system revision number. .It Dv KERN_OSTYPE The system type string. .It Dv KERN_PATH_MAX The maximum number of bytes in a pathname. .It Dv KERN_PIPE_BUF The maximum number of bytes which will be written atomically to a pipe. .It Dv KERN_POSIX1 The version of ISO/IEC 9945 (POSIX 1003.1) with which the system attempts to comply. .It Dv KERN_PROC Return the entire process table, or a subset of it. An array of .Li struct kinfo_proc structures is returned, whose size depends on the current number of such objects in the system. The third and fourth level names are as follows: .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent .It Sy Third level name Fourth level is: .It Dv KERN_PROC_ALL No " None" .It Dv KERN_PROC_PID No " A process ID" .It Dv KERN_PROC_PGRP No " A process group" .It Dv KERN_PROC_TTY No " A tty device" .It Dv KERN_PROC_UID No " A user ID" .It Dv KERN_PROC_RUID No " A real user ID" .El .It Dv KERN_PROF Return profiling information about the kernel. If the kernel is not compiled for profiling, attempts to retrieve any of the .Dv KERN_PROF values will fail with .Er EOPNOTSUPP . The third level names for the string and integer profiling information is detailed below. The changeable column shows whether a process with appropriate privileges may change the value. .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent .It Sy Third level name Type Changeable .It Dv GPROF_STATE No " integer yes" .It Dv GPROF_COUNT No " u_short[\|] yes" .It Dv GPROF_FROMS No " u_short[\|] yes" .It Dv GPROF_TOS No " struct tostruct yes" .It Dv GPROF_GMONPARAM No " struct gmonparam no" .El .Pp The variables are as follows: .Bl -tag -width "123456" .It Dv GPROF_STATE Returns .Dv GMON_PROF_ON or .Dv GMON_PROF_OFF to show that profiling is running or stopped. .It Dv GPROF_COUNT Array of statistical program counter counts. .It Dv GPROF_FROMS Array indexed by program counter of call-from points. .It Dv GPROF_TOS Array of .Li struct tostruct describing destination of calls and their counts. .It Dv GPROF_GMONPARAM Structure giving the sizes of the above arrays. .El .It Dv KERN_RAWPARTITION The raw partition of a disk (a == 0). .It Dv KERN_RND Returns statistics about the .Pa /dev/random device in a .Li struct rndstats structure. .It Dv KERN_SAVED_IDS Returns 1 if saved set-group-ID and saved set-user-ID are available. .It Dv KERN_SECURELVL The system security level. This level may be raised by processes with appropriate privileges. It may only be lowered by process 1. .It Dv KERN_SYSVMSG Returns 1 if System V style message queue functionality is available on this system, otherwise 0. .It Dv KERN_SYSVSEM Returns 1 if System V style semaphore functionality is available on this system, otherwise 0. .It Dv KERN_SYSVSHM Returns 1 if System V style share memory functionality is available on this system, otherwise 0. .It Dv KERN_VDISABLE Returns the terminal character disabling value. .It Dv KERN_VERSION The system version string. .It Dv KERN_VNODE Return the entire vnode table. Note, the vnode table is not necessarily a consistent snapshot of the system. The returned data consists of an array whose size depends on the current number of such objects in the system. Each element of the array contains the kernel address of a vnode .Li struct vnode * followed by the vnode itself .Li struct vnode . .El .Ss CTL_MACHDEP The set of variables defined is architecture dependent. Most architectures define at least the following variables. .Bl -column "CONSOLE_DEVICEXXX" "integerXXX" -offset indent .It Sy Second level name Type Changeable .It Dv CPU_CONSDEV No " dev_t no" .El .Ss CTL_NET The string and integer information available for the .Dv CTL_NET level is detailed below. The changeable column shows whether a process with appropriate privileges may change the value. .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent .It Sy Second level name Type Changeable .It Dv PF_ROUTE No " routing messages no" .It Dv PF_INET No " internet values yes" .It Dv PF_ENCAP No " IPsec values yes" .El .Pp .Bl -tag -width "123456" .It Dv PF_ENCAP Get or set various global information about the .Tn IP security protocols. The third level name is the protocol. The fourth level name is the variable name. The currently defined protocols and names are: .Bl -column "Protocol name" "Variable name" "integer" -offset indent .It Sy Protocol name Variable name Type Changeable .It encap encdebug integer yes .El .Pp The variables are as follows: .Bl -tag -width "123456" .It Li encap.encdebug Returns 1 when error message reporting is enabled for the host. If the kernel has been compiled with the .Dv ENCDEBUG option, then debugging information will also be reported when this variable is set. .El .It Dv PF_ROUTE Return the entire routing table or a subset of it. The data is returned as a sequence of routing messages (see .Xr route 4 for the header file, format, and meaning). The length of each message is contained in the message header. .Pp The third level name is a protocol number, which is currently always 0. The fourth level name is an address family, which may be set to 0 to select all address families. The fifth and sixth level names are as follows: .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent .It Sy Fifth level name Sixth level is: .It Dv NET_RT_FLAGS No " rtflags" .It Dv NET_RT_DUMP No " None" .It Dv NET_RT_IFLIST No " None" .El .It Dv PF_INET Get or set various global information about the internet protocols. The third level name is the protocol. The fourth level name is the variable name. The currently defined protocols and names are: .Bl -column "Protocol name" "Variable name" "integer" -offset indent .It Sy Protocol name Variable name Type Changeable .It ip forwarding integer yes .It ip redirect integer yes .It ip ttl integer yes .It icmp maskrepl integer yes .It tcp rfc1323 integer yes .It tcp baddynamic array yes .It tcp ident structure no .It tcp sack integer yes .It tcp mssdflt integer yes .It udp checksum integer yes .It udp baddynamic array yes .El .Pp The variables are as follows: .Bl -tag -width "123456" .It Li ip.forwarding Returns 1 when .Tn IP forwarding is enabled for the host, indicating the host is acting as a router. .It Li ip.redirect Returns 1 when .Tn ICMP redirects may be sent by the host. This option is ignored unless the host is routing .Tn IP packets, and should normally be enabled on all systems. .It Li ip.ttl The maximum time-to-live (hop count) value for an .Tn IP packet sourced by the system. This value applies to normal transport protocols, not to .Tn ICMP . .It Li icmp.maskrepl Returns 1 if .Tn ICMP network mask requests are to be answered. .It Li tcp.rfc1323 Returns 1 if RFC1323 extensions to .Tn TCP are enabled. .It Li tcp.baddynamic An array of .Li in_port_t is returned specifying the bitmask of .Tn TCP ports between 512 and 1023 inclusive that should not be allocated dynamically by the kernel (i.e., they must be bound specifically by port number). .It Li tcp.ident A structure .Li struct tcp_ident_mapping specifying a local and foreign endpoint of a .Tn TCP socket is filled in with the euid and ruid of the process that owns the socket. If no such socket exists then the euid and ruid values are both set to \-1. .It Li tcp.sack Returns 1 if RFC2018 Selective Acknowledgements are enabled. .It Li tcp.mssdflt The maximum segment size that is used as default for non local connections. The default value is 512. .It Li udp.checksum Returns 1 when .Tn UDP checksums are being computed and checked. Disabling .Tn UDP checksums is strongly discouraged. .It Li udp.baddynamic Analogous to .Li tcp.baddynamic but for .Tn UDP sockets. .El .El .Ss CTL_USER The string and integer information available for the .Dv CTL_USER level is detailed below. The changeable column shows whether a process with appropriate privileges may change the value. .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent .It Sy Second level name Type Changeable .It Dv USER_BC_BASE_MAX No " integer no" .It Dv USER_BC_DIM_MAX No " integer no" .It Dv USER_BC_SCALE_MAX No " integer no" .It Dv USER_BC_STRING_MAX No " integer no" .It Dv USER_COLL_WEIGHTS_MAX No " integer no" .It Dv USER_CS_PATH No " string no" .It Dv USER_EXPR_NEST_MAX No " integer no" .It Dv USER_LINE_MAX No " integer no" .It Dv USER_POSIX2_CHAR_TERM No " integer no" .It Dv USER_POSIX2_C_BIND No " integer no" .It Dv USER_POSIX2_C_DEV No " integer no" .It Dv USER_POSIX2_FORT_DEV No " integer no" .It Dv USER_POSIX2_FORT_RUN No " integer no" .It Dv USER_POSIX2_LOCALEDEF No " integer no" .It Dv USER_POSIX2_SW_DEV No " integer no" .It Dv USER_POSIX2_UPE No " integer no" .It Dv USER_POSIX2_VERSION No " integer no" .It Dv USER_RE_DUP_MAX No " integer no" .It Dv USER_STREAM_MAX No " integer no" .It Dv USER_TZNAME_MAX No " integer no" .El .Bl -tag -width "123456" .Pp .It Dv USER_BC_BASE_MAX The maximum ibase/obase values in the .Xr bc 1 utility. .It Dv USER_BC_DIM_MAX The maximum array size in the .Xr bc 1 utility. .It Dv USER_BC_SCALE_MAX The maximum scale value in the .Xr bc 1 utility. .It Dv USER_BC_STRING_MAX The maximum string length in the .Xr bc 1 utility. .It Dv USER_COLL_WEIGHTS_MAX The maximum number of weights that can be assigned to any entry of the .Dv LC_COLLATE order keyword in the locale definition file. .It Dv USER_CS_PATH Return a value for the .Ev PATH environment variable that finds all the standard utilities. .It Dv USER_EXPR_NEST_MAX The maximum number of expressions that can be nested within parenthesis by the .Xr expr 1 utility. .It Dv USER_LINE_MAX The maximum length in bytes of a text-processing utility's input line. .It Dv USER_POSIX2_CHAR_TERM Return 1 if the system supports at least one terminal type capable of all operations described in POSIX 1003.2, otherwise 0. .It Dv USER_POSIX2_C_BIND Return 1 if the system's C-language development facilities support the C-Language Bindings Option, otherwise 0. .It Dv USER_POSIX2_C_DEV Return 1 if the system supports the C-Language Development Utilities Option, otherwise 0. .It Dv USER_POSIX2_FORT_DEV Return 1 if the system supports the FORTRAN Development Utilities Option, otherwise 0. .It Dv USER_POSIX2_FORT_RUN Return 1 if the system supports the FORTRAN Runtime Utilities Option, otherwise 0. .It Dv USER_POSIX2_LOCALEDEF Return 1 if the system supports the creation of locales, otherwise 0. .It Dv USER_POSIX2_SW_DEV Return 1 if the system supports the Software Development Utilities Option, otherwise 0. .It Dv USER_POSIX2_UPE Return 1 if the system supports the User Portability Utilities Option, otherwise 0. .It Dv USER_POSIX2_VERSION The version of POSIX 1003.2 with which the system attempts to comply. .It Dv USER_RE_DUP_MAX The maximum number of repeated occurrences of a regular expression permitted when using interval notation. .It Dv USER_STREAM_MAX The maximum number of streams that a process may have open at any one time. .It Dv USER_TZNAME_MAX The minimum maximum number of types supported for the name of a timezone. .El .Ss CTL_VM The string and integer information available for the .Dv CTL_VM level is detailed below. The changeable column shows whether a process with appropriate privileges may change the value. .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent .It Sy Second level name Type Changeable .It Dv VM_LOADAVG No " struct loadavg no" .It Dv VM_METER No " struct vmtotal no" .El .Pp .Bl -tag -width "123456" .It Dv VM_LOADAVG Return the load average history. The returned data consists of a .Li struct loadavg . .It Dv VM_METER Return the system wide virtual memory statistics. The returned data consists of a .Li struct vmtotal . .El .Sh RETURN VALUES If the call to .Fn sysctl is unsuccessful, \-1 is returned and .Va errno is set appropriately. .Sh ERRORS The following errors may be reported: .Bl -tag -width Er .It Bq Er EFAULT The buffer .Fa name , .Fa oldp , .Fa newp , or length pointer .Fa oldlenp contains an invalid address. .It Bq Er EINVAL The .Fa name array is less than two or greater than .Dv CTL_MAXNAME . .It Bq Er EINVAL A non-null .Fa newp pointer is given and its specified length in .Fa newlen is too large or too small. .It Bq Er ENOMEM The length pointed to by .Fa oldlenp is too short to hold the requested value. .It Bq Er ENOTDIR The .Fa name array specifies an intermediate rather than terminal name. .It Bq Er EOPNOTSUPP The .Fa name array specifies a value that is unknown. .It Bq Er EPERM An attempt is made to set a read-only value. .It Bq Er EPERM A process without appropriate privileges attempts to set a value. .It Bq Er EPERM An attempt to change a value protected by the current kernel security level is made. .El .Sh FILES .Bl -tag -width -compact .It Aq Pa sys/sysctl.h definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers .It Aq Pa sys/socket.h definitions for second level network identifiers .It Aq Pa sys/gmon.h definitions for third level profiling identifiers .It Aq Pa vm/vm_param.h definitions for second level virtual memory identifiers .It Aq Pa netinet/in.h definitions for third level Internet identifiers and fourth level .Tn IP identifiers .It Aq Pa netinet/icmp_var.h definitions for fourth level .Tn ICMP identifiers .It Aq Pa netinet/tcp_var.h definitions for fourth level .Tn TCP identifiers .It Aq Pa netinet/udp_var.h definitions for fourth level .Tn UDP identifiers .El .Sh SEE ALSO .Xr sysctl 8 .Sh HISTORY The .Fn sysctl function first appeared in .Bx 4.4 .