xref: /csrg-svn/lib/libc/gen/sysctl.3 (revision 59868)

.\" Copyright (c) 1993 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.roff%
.\"
.\"	@(#)sysctl.3	6.4 (Berkeley) 05/10/93
.\"
.Dd ""
.Dt SYSCTL 3
.Os
.Sh NAME
.Nm sysctl
.Nd get or set system information
.Sh SYNOPSIS
.Fd #include <sys/sysctl.h>
.Ft int
.Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
.Sh DESCRIPTION
The
.Nm sysctl
function retrieves system information and allows processes with
appropriate privileges to set system information.
The information available from
.Nm sysctl
consists of integers, strings, and tables.
Unless explicitly noted below,
.Nm sysctl
returns a consistent snapshot of the data requested
Information may be retrieved and set from the command interface
using the
.Xr sysctl 1
utility.
.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 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 EINVAL.
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
.Nm sysctl
with a NULL parameter for
.Fa oldp .
The size of the available data be returned in the location pointed to by
.Fa oldlenp .
For some operations, the amount of space may change often;
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 <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 namesXXX" -offset indent
.It Sy Pa Name	Next level names	Description
.It CTL\_DEBUG	sys/sysctl.h	Debugging
.It CTL\_FS	sys/sysctl.h	File system
.It CTL\_HW	sys/sysctl.h	Generic CPU, I/O
.It CTL\_KERN	sys/sysctl.h	High kernel: processes, 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:
.Bd -literal -offset indent -compact
int mib[2], maxproc;
size_t len;
.sp
mib[0] = CTL_KERN;
mib[1] = KERN_MAXPROC;
len = sizeof(maxproc);
sysctl(mib, 2, &maxproc, &len, NULL, 0);
.Ed
.sp
To retrieve the standard search path for the system utilities:
.Bd -literal -offset indent -compact
int mib[2];
size_t len;
char *p;
.sp
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 RETURN VALUES
If the call to
.Nm sysctl
is successful, 0 is returned.
Otherwise \-1 is returned and
.Va errno
is set appropriately.
.Sh CTL_DEBUG
There are currently no second level names for the debugging interface.
.Sh CTL_FS
There are currently no second level names for the file system.
.Sh CTL_HW
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.
.Bl -column "Second level nameXXX" 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\_DISKNAMES	integer	no
.\".It HW\_DISKSTATS	integer	no
.El
.Pp
.Bl -tag -width "123456"
.It Li HW_MACHINE
Return the machine class.
.It Li HW_MODEL
Return the machine model
.It Li HW_NCPU
Return the number of cpus.
.It Li HW_BYTEORDER
Return the byteorder (4,321, or 1,234).
.It Li HW_PHYSMEM
Return the bytes of physical memory.
.It Li HW_USERMEM
Return the bytes of non-kernel memory.
.It Li HW_PAGESIZE
Return the software page size.
.\".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.
Consistency in the kernel tables is obtained by locking the destination
buffer into memory so that the data may be copied out without blocking.
Calls are serialized to avoid deadlock.
.Bl -column "KERNXCHOWNXRESTRICTEDXXX" "struct clockrateXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It KERN\_ARGMAX	integer	no
.It KERN\_CHOWN\_RESTRICTED	integer	no
.It KERN\_CLOCKRATE	struct clockinfo	yes
.It KERN\_FILE	struct file	yes
.It KERN\_HOSTID	integer	yes
.It KERN\_HOSTNAME	string	yes
.It KERN\_JOB\_CONTROL	integer	no
.It KERN\_LINK\_MAX	integer	no
.It KERN\_MAXFILES	integer	yes
.It KERN\_MAXPROC	integer	yes
.It KERN\_MAXVNODES	integer	no
.It KERN\_MAX\_CANON	integer	no
.It KERN\_MAX\_INPUT	integer	no
.It KERN\_NAME\_MAX	integer	no
.It KERN\_NGROUPS	integer	no
.It KERN\_NO\_TRUNC	integer	no
.It KERN\_OSRELEASE	string	no
.It KERN\_OSREV	integer	no
.It KERN\_OSTYPE	string	no
.It KERN\_PATH\_MAX	integer	no
.It KERN\_PIPE\_BUF	integer	no
.It KERN\_POSIX1	integer	no
.It KERN\_PROC	struct proc	yes
.It KERN\_PROF	node	yes
.It KERN\_SAVED\_IDS	integer	no
.It KERN\_SECURELVL	integer	raise only
.It KERN\_VDISABLE	integer	no
.It KERN\_VERSION	string	no
.It KERN\_VNODE	struct vnode	yes
.El
.Pp
.Bl -tag -width "123456"
.It Li KERN_ARGMAX
Maximum bytes of argument to exec.
.It Li KERN_CHOWN_RESTRICTED
Return 1 if appropriate privileges are required for the
.Xr chown 2
system call, otherwise 0.
.It Li KERN_CLOCKRATE
A
.Ns ( Li struct clockinfo Ns )
structure is returned.
This structure contains the clock, statistics clock and profiling clock
frequencies, and the number of micro-seconds per hz tick.
.It Li KERN_FILE
Return the entire file table.
The returned data consists of a single
.Ns ( Li struct filehead Ns )
followed by an array of
.Ns ( Li struct file Ns ) ,
whose size depends on the current number of such objects in the system.
.It Li KERN_HOSTID
Return the host id.
.It Li KERN_HOSTNAME
Return the hostname.
.It Li KERN_JOB_CONTROL
Return 1 if job control is available on this system, otherwise 0.
.It Li KERN_LINK_MAX
Return the maximum file link count.
.It Li KERN_MAXFILES
Return the maximum number of open files a process may have.
.It Li KERN_MAXPROC
Return the maximum number of simultaneous processes a user may have.
.It Li KERN_MAXVNODES
Return the maximum number of vnodes available on the system.
.It Li KERN_MAX_CANON
Return the maximum number of bytes in terminal canonical input line.
.It Li KERN_MAX_INPUT
Return the minimum number of bytes for which space is available in
a terminal input queue.
.It Li KERN_NAME_MAX
Maximum number of bytes in a file name.
.It Li KERN_NGROUPS
Maximum number of supplemental groups.
.It Li KERN_NO_TRUNC
Return 1 if too long pathnames are truncated.
.It Li KERN_OSRELEASE
Return the system release string.
.It Li KERN_OSREV
Return the system revision string.
.It Li KERN_OSTYPE
Return the system type string.
.It Li KERN_PATH_MAX
Maximum number of bytes in a pathname.
.It Li KERN_PIPE_BUF
Maximum number of bytes which will be written atomically to a pipe.
.It Li KERN_POSIX1
Return the POSIX 1003.1 version with which the system attempts to comply.
.It Li KERN_PROC
Return the entire process table, or a subset of it.
An array of
.Ns ( Li struct kinfo_proc Ns )
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 nameXXX" "Fourth level is:XXX" -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 kernel profiling information.
The only currently available third level name is GPROF_STATE, which
returns 1 if the kernel was compiled for profiling, and 0 if it was
not.
.It Li KERN_SAVED_IDS
Returns 1 if saved set-group and saved set-user ID is available.
.It Li KERN_SECURELVL
Returns the system security level.
This level may be raised by processes with appropriate privilege.
.It Li KERN_VDISABLE
Returns the terminal character disabling value.
.It Li KERN_VERSION
Return 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
.Ns ( Li struct vnode * Ns )
followed by the vnode itself
.Ns ( Li struct vnode Ns ) .
.El
.Sh CTL_MACHDEP
There are currently no second level names for the machine dependent
interface.
.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 nameXXX" "routine messagesXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It PF\_ROUTE	routine messages	no
.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 nameXXX" "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
.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 "Second level nameXXX" "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
.El
.Bl -tag -width "123456"
.Pp
.It Li USER_BC_BASE_MAX
Return the maximum ibase/obase values in the
.Xr bc 1
utility
.It Li USER_BC_DIM_MAX
Return the maximum array size in the
.Xr bc 1
utility.
.It Li USER_BC_SCALE_MAX
Return the maximum scale value in the
.Xr bc 1
utility.
.It Li USER_BC_STRING_MAX
Return the maximum string length in the
.Xr bc 1
utility.
.It Li USER_COLL_WEIGHTS_MAX
Return 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 of the standard utilities.
.It Li USER_EXPR_NEST_MAX
Return the maximum number of expressions that can be nested within
parenthesis by the
.Xr expr 1
utility.
.It Li USER_LINE_MAX
Return 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
Return the POSIX 1003.2 version with which the system attempts to comply.
.It Li USER_RE_DUP_MAX
Return the maximum number of repeated occurrences of a regular expression
permitted when using interval notation.
.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 nameXXX" "struct loadavgXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It VM\_LOADAVG	struct loadavg	no
.It VM\_METER	struct vmtotal	no
.El
.Pp
.Bl -tag -width "123456"
.It Li VM_LOADAVG
Return the load average history.
The returned data consists of a
.Ns ( Li struct loadavg Ns ) .
.It Li VM_METER
Return the system wide virtual memory statistics.
The returned data consists of a
.Ns ( Li struct vmtotal Ns ) .
.El
.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 <vm/vmXparam.h> -compact
.It Pa <sys/sysctl.h>
definitions for top level identifiers, second level kernel and hardware
identifiers, user level identifiers
.It Pa <sys/socket.h>
definitions for second level network identifiers
.It Pa <vm/vm_param.h>
definitions for second level virtual memory identifiers
.El
.Sh SEE ALSO
.Xr sysctl 8
.Sh HISTORY
The
.Nm sysctl
function first appeared in 4.4BSD.