.\" 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. .\" .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95 .\" $FreeBSD$ .\" .Dd May 9, 1995 .Dt SYSCTL 3 .Os .Sh NAME .Nm sysctl , .Nm sysctlbyname .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" .Ft int .Fn sysctlbyname "const char *name" "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 ``Management Information Base'' (MIB) style name, listed in .Fa name , which is a .Fa namelen length array of integers. .Pp The .Fn sysctlbyname function accepts an ASCII representation of the name and internally looks up the integer name vector. Apart from that, it behaves the same as the standard .Fn sysctl function. .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 and after a call that returns with the error code ENOMEM. 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 ENOMEM. If the old value is not desired, .Fa oldp and .Fa oldlenp should be set to NULL. .Pp The size of the available data can be determined by calling .Fn sysctl with a 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 NULL and .Fa newlen set to 0. .Pp The top level names are defined with a CTL_ prefix in .Pa , 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 Pa Name Next level names Description .It CTL\_DEBUG sys/sysctl.h Debugging .It CTL\_VFS sys/mount.h Filesystem .It CTL\_HW sys/sysctl.h Generic CPU, I/O .It CTL\_KERN sys/sysctl.h High kernel limits .It CTL\_MACHDEP sys/sysctl.h Machine dependent .It CTL\_NET sys/socket.h Networking .It CTL\_USER sys/sysctl.h User-level .It CTL\_VM 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 .Sh 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 .Ns ( Va struct ctldebug ) variables named .Nm debug0 through .Nm 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 .Nm dospecialcheck as a debugging variable, the following declaration would be used: .Bd -literal -offset indent -compact int dospecialcheck = 1; struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; .Ed .Sh CTL_VFS A distinguished second level name, VFS_GENERIC, is used to get general information about all filesystems. One of its third level identifiers is VFS_MAXTYPENUM that gives the highest valid filesystem type number. Its other third level identifier is VFS_CONF that returns configuration information about the filesystem type given as a fourth level identifier (see .Xr getvfsbyname 3 as an example of its use). The remaining second level identifiers are the filesystem type number returned by a .Xr statfs 2 call or from VFS_CONF. The third level identifiers available for each filesystem are given in the header file that defines the mount argument structure for that filesystem. .Sh CTL_HW The string and integer information available for the CTL_HW level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "Second level nameXXXXXX" integerXXX -offset indent .It Sy Pa Second level name Type Changeable .It HW\_MACHINE string no .It HW\_MODEL string no .It HW\_NCPU integer no .It HW\_BYTEORDER integer no .It HW\_PHYSMEM integer no .It HW\_USERMEM integer no .It HW\_PAGESIZE integer no .It HW\_FLOATINGPOINT integer no .It HW\_MACHINE\_ARCH string no .\".It HW\_DISKNAMES integer no .\".It HW\_DISKSTATS integer no .El .Pp .Bl -tag -width "123456" .It Li HW_MACHINE The machine class. .It Li HW_MODEL The machine model .It Li HW_NCPU The number of cpus. .ne 1i .It Li HW_BYTEORDER The byteorder (4,321, or 1,234). .It Li HW_PHYSMEM The bytes of physical memory. .It Li HW_USERMEM The bytes of non-kernel memory. .It Li HW_PAGESIZE The software page size. .It Li HW_FLOATINGPOINT Nonzero if the floating point support is in hardware. .It Li HW_MACHINE_ARCH The machine dependent architecture type. .\".It Fa HW_DISKNAMES .\".It Fa HW_DISKSTATS .El .Sh CTL_KERN The string and integer information available for the CTL_KERN level is detailed below. The changeable column shows whether a process with appropriate privilege 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 "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent .It Sy Pa Second level name Type Changeable .It KERN\_ARGMAX integer no .It KERN\_BOOTFILE string yes .It KERN\_BOOTTIME struct timeval no .It KERN\_CLOCKRATE struct clockinfo no .It KERN\_FILE struct file no .It KERN\_HOSTID integer yes .It KERN\_HOSTNAME string yes .It KERN\_JOB\_CONTROL integer no .It KERN\_MAXFILES integer yes .It KERN\_MAXFILESPERPROC integer yes .It KERN\_MAXPROC integer no .It KERN\_MAXPROCPERUID integer yes .It KERN\_MAXVNODES integer yes .It KERN\_NGROUPS integer no .It KERN\_NISDOMAINNAME string yes .It KERN\_OSRELDATE integer no .It KERN\_OSRELEASE string no .It KERN\_OSREV integer no .It KERN\_OSTYPE string no .It KERN\_POSIX1 integer no .It KERN\_PROC struct proc no .It KERN\_PROF node not applicable .It KERN\_SAVED\_IDS integer no .It KERN\_SECURELVL integer raise only .It KERN\_UPDATEINTERVAL integer no .It KERN\_VERSION string no .It KERN\_VNODE struct vnode no .El .ne 1i .Pp .Bl -tag -width "123456" .It Li KERN_ARGMAX The maximum bytes of argument to .Xr execve 2 . .It Li KERN_BOOTFILE The full pathname of the file from which the kernel was loaded. .It Li KERN_BOOTTIME A .Va struct timeval structure is returned. This structure contains the time that the system was booted. .It Li KERN_CLOCKRATE A .Va 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 skew rate. .It Li KERN_FILE Return the entire file table. The returned data consists of a single .Va struct filehead followed by an array of .Va struct file , whose size depends on the current number of such objects in the system. .It Li KERN_HOSTID Get or set the host id. .It Li KERN_HOSTNAME Get or set the hostname. .It Li KERN_JOB_CONTROL Return 1 if job control is available on this system, otherwise 0. .It Li KERN_MAXFILES The maximum number of files that may be open in the system. .It Li KERN_MAXFILESPERPROC The maximum number of files that may be open for a single process. This limit only applies to processes with an effective uid of nonzero at the time of the open request. Files that have already been opened are not affected if the limit or the effective uid is changed. .It Li KERN_MAXPROC The maximum number of concurrent processes the system will allow. .It Li KERN_MAXPROCPERUID The maximum number of concurrent processes the system will allow for a single effective uid. This limit only applies to processes with an effective uid of nonzero at the time of a fork request. Processes that have already been started are not affected if the limit is changed. .It Li KERN_MAXVNODES The maximum number of vnodes available on the system. .It Li KERN_NGROUPS The maximum number of supplemental groups. .It Li KERN_NISDOMAINNAME The name of the current YP/NIS domain. .It Li KERN_OSRELDATE The system release date in YYYYMM format (January 1996 is encoded as 199601). .It Li KERN_OSRELEASE The system release string. .It Li KERN_OSREV The system revision string. .It Li KERN_OSTYPE The system type string. .It Li KERN_POSIX1 The version of ISO/IEC 9945 (POSIX 1003.1) with which the system attempts to comply. .It Li KERN_PROC Return the entire process table, or a subset of it. An array of .Va 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 Pa Third level name Fourth level is: .It KERN\_PROC\_ALL None .It KERN\_PROC\_PID A process ID .It KERN\_PROC\_PGRP A process group .It KERN\_PROC\_TTY A tty device .It KERN\_PROC\_UID A user ID .It KERN\_PROC\_RUID A real user ID .El .It Li KERN_PROF Return profiling information about the kernel. If the kernel is not compiled for profiling, attempts to retrieve any of the KERN_PROF values will fail with EOPNOTSUPP. The third level names for the string and integer profiling information is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent .It Sy Pa Third level name Type Changeable .It GPROF\_STATE integer yes .It GPROF\_COUNT u_short[\|] yes .It GPROF\_FROMS u_short[\|] yes .It GPROF\_TOS struct tostruct yes .It GPROF\_GMONPARAM struct gmonparam no .El .Pp The variables are as follows: .Bl -tag -width "123456" .It Li GPROF_STATE Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling is running or stopped. .It Li GPROF_COUNT Array of statistical program counter counts. .It Li GPROF_FROMS Array indexed by program counter of call-from points. .It Li GPROF_TOS Array of .Va struct tostruct describing destination of calls and their counts. .It Li GPROF_GMONPARAM Structure giving the sizes of the above arrays. .El .ne 1i .It Li KERN_SAVED_IDS Returns 1 if saved set-group and saved set-user ID is available. .It Li KERN_SECURELVL The system security level. This level may be raised by processes with appropriate privilege. It may not be lowered. .It Li KERN_VERSION The system version string. .It Li 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 .Va struct vnode * followed by the vnode itself .Va struct vnode . .It Li KERN_UPDATEINTERVAL The interval between .Xr sync 2 calls in the .Xr update 4 process. .El .Sh CTL_MACHDEP The set of variables defined is architecture dependent. The following variables are defined for the i386 architecture. .Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent .It Sy Pa Second level name Type Changeable .It Li CPU_CONSDEV dev_t no .It Li CPU_ADJKERNTZ int yes .It Li CPU_DISRTCSET int yes .It Li CPU_BOOTINFO struct bootinfo no .It Li CPU_WALLCLOCK int yes .El .Sh CTL_NET The string and integer information available for the CTL_NET level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent .It Sy Pa Second level name Type Changeable .It PF\_ROUTE routing messages no .It PF\_INET internet values yes .El .Pp .Bl -tag -width "123456" .It Li 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 Pa Fifth level name Sixth level is: .It NET\_RT\_FLAGS rtflags .It NET\_RT\_DUMP None .It NET\_RT\_IFLIST None .El .It Li 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: .ne 1i .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX .It Pa Protocol Variable Type Changeable .It icmp bmcastecho integer yes .It icmp maskrepl integer yes .It ip forwarding integer yes .It ip redirect integer yes .It ip ttl integer yes .It udp checksum integer yes .El .Pp The variables are as follows: .Bl -tag -width "123456" .It Li icmp.bmcastecho Returns 1 if an ICMP echo request to a broadcast or multicast address is to be answered. .It Li icmp.maskrepl Returns 1 if ICMP network mask requests are to be answered. .It Li ip.forwarding Returns 1 when IP forwarding is enabled for the host, meaning that the host is acting as a router. .It Li ip.redirect Returns 1 when ICMP redirects may be sent by the host. This option is ignored unless the host is routing IP packets, and should normally be enabled on all systems. .It Li ip.ttl The maximum time-to-live (hop count) value for an IP packet sourced by the system. This value applies to normal transport protocols, not to ICMP. .It Li udp.checksum Returns 1 when UDP checksums are being computed and checked. Disabling UDP checksums is strongly discouraged. .El .Sh CTL_USER The string and integer information available for the CTL_USER level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent .It Sy Pa Second level name Type Changeable .It USER\_BC\_BASE\_MAX integer no .It USER\_BC\_DIM\_MAX integer no .It USER\_BC\_SCALE\_MAX integer no .It USER\_BC\_STRING\_MAX integer no .It USER\_COLL\_WEIGHTS\_MAX integer no .It USER\_CS\_PATH string no .It USER\_EXPR\_NEST\_MAX integer no .It USER\_LINE\_MAX integer no .It USER\_POSIX2\_CHAR\_TERM integer no .It USER\_POSIX2\_C\_BIND integer no .It USER\_POSIX2\_C\_DEV integer no .It USER\_POSIX2\_FORT\_DEV integer no .It USER\_POSIX2\_FORT\_RUN integer no .It USER\_POSIX2\_LOCALEDEF integer no .It USER\_POSIX2\_SW\_DEV integer no .It USER\_POSIX2\_UPE integer no .It USER\_POSIX2\_VERSION integer no .It USER\_RE\_DUP\_MAX integer no .It USER\_STREAM\_MAX integer no .It USER\_TZNAME\_MAX integer no .El .Bl -tag -width "123456" .Pp .It Li USER_BC_BASE_MAX The maximum ibase/obase values in the .Xr bc 1 utility. .It Li USER_BC_DIM_MAX The maximum array size in the .Xr bc 1 utility. .It Li USER_BC_SCALE_MAX The maximum scale value in the .Xr bc 1 utility. .It Li USER_BC_STRING_MAX The maximum string length in the .Xr bc 1 utility. .It Li USER_COLL_WEIGHTS_MAX The maximum number of weights that can be assigned to any entry of the LC_COLLATE order keyword in the locale definition file. .It Li USER_CS_PATH Return a value for the .Ev PATH environment variable that finds all the standard utilities. .It Li USER_EXPR_NEST_MAX The maximum number of expressions that can be nested within parenthesis by the .Xr expr 1 utility. .It Li USER_LINE_MAX The maximum length in bytes of a text-processing utility's input line. .It Li 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 Li USER_POSIX2_C_BIND Return 1 if the system's C-language development facilities support the C-Language Bindings Option, otherwise 0. .It Li USER_POSIX2_C_DEV Return 1 if the system supports the C-Language Development Utilities Option, otherwise 0. .It Li USER_POSIX2_FORT_DEV Return 1 if the system supports the FORTRAN Development Utilities Option, otherwise 0. .It Li USER_POSIX2_FORT_RUN Return 1 if the system supports the FORTRAN Runtime Utilities Option, otherwise 0. .It Li USER_POSIX2_LOCALEDEF Return 1 if the system supports the creation of locales, otherwise 0. .It Li USER_POSIX2_SW_DEV Return 1 if the system supports the Software Development Utilities Option, otherwise 0. .It Li USER_POSIX2_UPE Return 1 if the system supports the User Portability Utilities Option, otherwise 0. .It Li USER_POSIX2_VERSION The version of POSIX 1003.2 with which the system attempts to comply. .It Li USER_RE_DUP_MAX The maximum number of repeated occurrences of a regular expression permitted when using interval notation. .ne 1i .It Li USER_STREAM_MAX The minimum maximum number of streams that a process may have open at any one time. .It Li USER_TZNAME_MAX The minimum maximum number of types supported for the name of a timezone. .El .Sh CTL_VM The string and integer information available for the CTL_VM level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent .It Sy Pa Second level name Type Changeable .It VM\_LOADAVG struct loadavg no .It VM\_METER struct vmtotal no .It VM\_PAGEOUT\_ALGORITHM integer yes .It VM\_SWAPPING\_ENABLED integer maybe .It VM\_V\_CACHE\_MAX integer yes .It VM\_V\_CACHE\_MIN integer yes .It VM\_V\_FREE\_MIN integer yes .It VM\_V\_FREE\_RESERVED integer yes .It VM\_V\_FREE\_TARGET integer yes .It VM\_V\_INACTIVE\_TARGET integer yes .It VM\_V\_PAGEOUT\_FREE\_MIN integer yes .El .Pp .Bl -tag -width "123456" .It Li VM_LOADAVG Return the load average history. The returned data consists of a .Va struct loadavg . .It Li VM_METER Return the system wide virtual memory statistics. The returned data consists of a .Va struct vmtotal . .It Li VM_PAGEOUT_ALGORITHM 0 if the statistics-based page management algorithm is in use or 1 if the near-LRU algorithm is in use. .It Li VM_SWAPPING_ENABLED 1 if process swapping is enabled or 0 if disabled. This variable is permanently set to 0 if the kernel was built with swapping disabled. .It Li VM_V_CACHE_MAX Maximum desired size of the cache queue. .It Li VM_V_CACHE_MIN Minimum desired size of the cache queue. If the cache queue size falls very far below this value, the pageout daemon is awakened. .It Li VM_V_FREE_MIN Minimum amount of memory (cache memory plus free memory) required to be available before a process waiting on memory will be awakened. .It Li VM_V_FREE_RESERVED Processes will awaken the pageout daemon and wait for memory if the number of free and cached pages drops below this value. .It Li VM_V_FREE_TARGET The total amount of free memory (including cache memory) that the pageout daemon tries to maintain. .It Li VM_V_INACTIVE_TARGET The desired number of inactive pages that the pageout daemon should achieve when it runs. Inactive pages can be quickly inserted into process address space when needed. .It Li VM_V_PAGEOUT_FREE_MIN If the amount of free and cache memory falls below this value, the pageout daemon will enter "memory conserving mode" to avoid deadlock. .El .Sh RETURN VALUES .Fn sysctl and .Fn sysctlbyname return 0 when successful. Otherwise \-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 CTL_MAXNAME. .It Bq Er EINVAL A non-null .Fa newp 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 privilege attempts to set a value. .El .Sh FILES .Bl -tag -width -compact .It Pa definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers .It Pa definitions for second level network identifiers .It Pa definitions for third level profiling identifiers .It Pa definitions for second level virtual memory identifiers .It Pa definitions for third level Internet identifiers and fourth level IP identifiers .It Pa definitions for fourth level ICMP identifiers .It Pa definitions for fourth level UDP identifiers .El .Sh SEE ALSO .Xr sysconf 3 , .Xr sysctl 8 .Sh HISTORY The .Fn sysctl function first appeared in .Bx 4.4 .