2.11BSD/src/man/man3/sysctl.3

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.\"	@(#)sysctl.3	8.1.1 (2.11BSD GTE) 1/13/95
.\"
.TH SYSCTL 3 "January 13, 1995"
.UC 4
.SH NAME
sysctl \- get or set system information
.SH SYNOPSIS
.nf
.ft B
#include <sys/sysctl.h>

int
sysctl(name, namelen, oldp, *oldlenp, *newp, newlen)
   int *name;
   u_int namelen;
   void *oldp;
   size_t *oldlenp;
   void *newp;
   size_t newlen
.ft R
.fi
.SH DESCRIPTION
The
\fBsysctl\fP
function retrieves system information and allows processes with
appropriate privileges to set system information.
The information available from
\fBsysctl\fP
consists of integers, strings, and tables.
Information may be retrieved and set from the command interface
using the 
\fIsysctl\fP(1)
utility.
.PP
Unless explicitly noted below,
\fBsysctl\fP
returns a consistent snapshot of the data requested.
Calls to
\fBsysctl\fP
are serialized to avoid deadlock.
.PP
The state is described using a ``Management Information Base'' (MIB)
style name, listed in
\fIname\fP ,
which is a
\fInamelen\fP
length array of integers.
.PP
The information is copied into the buffer specified by
\fIoldp\fP .
The size of the buffer is given by the location specified by
\fIoldlenp\fP
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 ENOMEM.
If the old value is not desired,
\fIoldp\fP
and
\fIoldlenp\fP
should be set to NULL.
.PP
The size of the available data can be determined by calling 
\fBsysctl\fP
with a NULL parameter for
\fIoldp\fP.
The size of the available data will be returned in the location pointed to by
\fIoldlenp\fP.
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,
\fInewp\fP
is set to point to a buffer of length
\fInewlen\fP
from which the requested value is to be taken.
If a new value is not to be set,
\fInewp\fP
should be set to NULL and
\fInewlen\fP
set to 0.
.PP
The top level names are defined with a CTL_ prefix in
\fI<sys/sysctl.h>\fP,
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
.nf
.ta .25i 1.5i 3.75i 4.5i
	Name	Next level names	Description
	CTL\_DEBUG	sys/sysctl.h	Debugging
	CTL\_FS	sys/sysctl.h	File system
	CTL\_HW	sys/sysctl.h	Generic CPU, I/O
	CTL\_KERN	sys/sysctl.h	High kernel limits
	CTL\_MACHDEP	sys/sysctl.h	Machine dependent
	CTL\_NET	sys/socket.h	Networking
	CTL\_USER	sys/sysctl.h	User-level
	CTL\_VM	vm/vm_param.h	Virtual memory
.fi
.PP
For example, the following retrieves the maximum number of processes allowed
in the system:
.sp
.nf
.in +.5i
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);
.in -.5i
.sp
To retrieve the standard search path for the system utilities:
.sp
.nf
.in +.5i
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);
.in -.5i
.fi
.SH CTL_DEBUG
The debugging variables vary from system to system.
A debugging variable may be added or deleted without need to recompile
\fBsysctl\fP
to know about it.
Each time it runs,
\fBsysctl\fP
gets the list of debugging variables from the kernel and
displays their current values.
The system defines twenty 
\fIstruct ctldebug\fP
variables named 
\fIdebug0\fP
through
\fIdebug19\fP.
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
\fIdospecialcheck\fP
as a debugging variable, the following declaration would be used:
.sp
.nf
.in +.5i
int dospecialcheck = 1;
struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
.in -.5i
.fi
.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_HW level
is detailed below.
The changeable column shows whether a process with appropriate
privilege may change the value.
.sp
.nf
.ta .25i 2.75i 3.75i
	Second level name	Type	Changeable
	HW\_MACHINE	string	no
	HW\_MODEL	string	no
	HW\_NCPU	integer	no
	HW\_BYTEORDER	integer	no
	HW\_PHYSMEM	integer	no
	HW\_USERMEM	integer	no
	HW\_PAGESIZE	integer	no
.\".It HW\_DISKNAMES	integer	no
.\".It HW\_DISKSTATS	integer	no
.fi
.PP
.ta .5i
HW_MACHINE
.br
	The machine class.
.sp
HW_MODEL
.br
	The machine model
.sp
HW_NCPU
.br
	The number of cpus.
.sp
HW_BYTEORDER
.br
	The byteorder (3412, 4321, or 1234).
.sp
HW_PHYSMEM
.br
	The bytes of physical memory.
.sp
HW_USERMEM
.br
	The bytes of non-kernel memory.
.sp
HW_PAGESIZE
.br
	The software page size.
.sp
.\".It Fa HW_DISKNAMES
.\".It Fa HW_DISKSTATS
.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 inodes, the open file entries, routing table entries,
virtual memory statistics, load average history, and clock rate
information.
.sp
.nf
.ta .25i 2.75i 4.5i

	Second level name	Type	Changeable
	KERN\_ARGMAX	integer	no
	KERN\_BOOTTIME	struct timeval	no
	KERN\_CHOWN\_RESTRICTED	integer	no
	KERN\_CLOCKRATE	struct clockinfo	no
	KERN\_FILE	struct file	no
	KERN\_HOSTID	long	yes
	KERN\_HOSTNAME	string	yes
	KERN\_JOB\_CONTROL	integer	no
.\"KERN\_LINK\_MAX	integer	no
	KERN\_MAXFILES	integer	no
	KERN\_MAXPROC	integer	no
	KERN\_MAXINODES	integer	no
	KERN\_MAXTEXTS	integer	no
.\"KERN\_MAX\_CANON	integer	no
.\"KERN\_MAX\_INPUT	integer	no
.\"KERN\_NAME\_MAX	integer	no
	KERN\_NGROUPS	integer	no
.\"KERN\_NO\_TRUNC	integer	no
	KERN\_OSRELEASE	string	no
	KERN\_OSREV	integer	no
	KERN\_OSTYPE	string	no
.\"KERN\_PATH\_MAX	integer	no
.\"KERN\_PIPE\_BUF	integer	no
	KERN\_POSIX1	integer	no
	KERN\_PROC	struct proc	no
	KERN\_PROF	node	not applicable
	KERN\_SAVED\_IDS	integer	no
	KERN\_SECURELVL	integer	raise only
	KERN\_TEXT	struct text	no
.\"KERN\_VDISABLE	integer	no
	KERN\_VERSION	string	no
	KERN\_INODE	struct inode	no
.fi
.PP
KERN_ARGMAX
.br
.in +.5i
The maximum bytes of argument to \fBexec(2)\fP.
.sp
.in -.5i
KERN_BOOTTIME
.br
.in +.5i
A \fIstruct timeval\fP structure is returned.
This structure contains the time that the system was booted.
.sp
.in -.5i
.\"KERN_CHOWN_RESTRICTED
.\"Return 1 if appropriate privileges are required for the
.\".Xr chown 2
.\"system call, otherwise 0.
KERN_CLOCKRATE
.br
.in +.5i
A \fIstruct clockinfo\fP structure is returned.
This structure contains the clock, statistics clock and profiling clock
frequencies, and the number of micro-seconds per hz tick.
.sp
.in -.5i
KERN_FILE
.br
.in +.5i
Return the entire file table as an array of extended \fIfile\fP
structures.
Each element of the array contains the kernel address of a file
\fIstruct inode *\fP
followed by the file itself
\fIstruct file\fP.  There can never be more than \fBKERN_MAXFILES\fP
inodes returned.
.sp
.in -.5i
KERN_HOSTID
.br
.in +.5i
Get or set the host id.
.sp
.in -.5i
KERN_HOSTNAME
.br
.in +.5i
Get or set the hostname.
.sp
.in -.5i
KERN_JOB_CONTROL
.br
.in +.5i
Return 1 if job control is available on this system, otherwise 0.
.sp
.in -.5i
.\"KERN_LINK_MAX
.\"The maximum file link count.
KERN_MAXFILES
.br
.in +.5i
The maximum number of open files that may be open in the system.
.sp
.in -.5i
KERN_MAXPROC
.br
.in +.5i
The maximum number of simultaneous processes the system will allow.
.sp
.in -.5i
KERN_MAXINODES
.br
.in +.5i
The maximum number of inodes available on the system.
.sp
.in -.5i
KERN_MAXTEXTS
.br
.in +.5i
The maximum number of text structures available on the system.
.sp
.in -.5i
.\"KERN_MAX_CANON
.\"The maximum number of bytes in terminal canonical input line.
.\"KERN_MAX_INPUT
.\"The minimum maximum number of bytes for which space is available in
.\"a terminal input queue.
.\"KERN_NAME_MAX
.\"The maximum number of bytes in a file name.
KERN_NGROUPS
.br
.in +.5i
The maximum number of supplemental groups.
.sp
.in -.5i
.\"KERN_NO_TRUNC
.\"Return 1 if file names longer than KERN_NAME_MAX are truncated.
KERN_OSRELEASE
.br
.in +.5i
The system release string.
.sp
.in -.5i
KERN_OSREV
.br
.in +.5i
The system revision string.
.sp
.in -.5i
KERN_OSTYPE
.br
.in +.5i
The system type string.
.sp
.in -.5i
.\"KERN_PATH_MAX
.\"The maximum number of bytes in a pathname.
.\"KERN_PIPE_BUF
.\"The maximum number of bytes which will be written atomically to a pipe.
KERN_POSIX1
.br
.in +.5i
The version of ISO/IEC 9945 (POSIX 1003.1) with which the system
attempts to comply.
.sp
.in -.5i
KERN_PROC
.br
.in +.5i
Return the entire process table, or a subset of it.
An array of
\fIstruct kinfo_proc\fP
structures is returned,
whose size depends on the current number of such objects in the system.
.sp
.in -.5i
The third and fourth level names are as follows:
.sp
.nf
.ta .25i 3.0i
	Third level name	Fourth level is:
	KERN\_PROC\_ALL	None
	KERN\_PROC\_PID	A process ID
	KERN\_PROC\_PGRP	A process group
	KERN\_PROC\_TTY	A tty device
	KERN\_PROC\_UID	A user ID
	KERN\_PROC\_RUID	A real user ID
	KERN\_PROF	Return kernel profiling information.
.fi
.sp
.in + .5i
If the kernel is not compiled for profiling,
attempts to retrieve any of the KERN_PROF values will
fail with EOPNOTSUPP.
.sp
.in -.5i
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.
.sp
.in +.5i
.nf
.ta .25i 2.25i 4.25i
Third level name	Type	Changeable
	GPROF\_STATE	integer	yes
	GPROF\_COUNT	u_short[\|]	yes
	GPROF\_FROMS	u_short[\|]	yes
	GPROF\_TOS	struct tostruct	yes
	GPROF\_GMONPARAM	struct gmonparam	no
.fi
.PP
The variables are as follows:
.sp
GPROF_STATE
.br
.in +.5i
Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
is running or stopped.
.sp
.in -.5i
GPROF_COUNT
.br
.in +.5i
Array of statistical program counter counts.
.sp
.in -.5i
GPROF_FROMS
.br
.in +.5i
Array indexed by program counter of call-from points.
.sp
.in -.5i
GPROF_TOS
.br
.in +.5i
Array of
\fIstruct tostruct\fP
describing destination of calls and their counts.
.sp
.in -.5i
GPROF_GMONPARAM
.br
.in +.5i
Structure giving the sizes of the above arrays.
.in -.5i
.sp
KERN_SAVED_IDS
.br
.in +.5i
Returns 1 if saved set-group and saved set-user ID is available.
.sp
.in -.5i
.in -.5i
KERN_SECURELVL
.br
.in +.5i
The system security level.
This level may be raised by processes with appropriate privilege.
It may only be lowered by process 1.
.sp
.in -.5i
.\"KERN_VDISABLE
.\"Returns the terminal character disabling value.
KERN_VERSION
.br
.in +.5i
The system version string.
.sp
.in -.5i
KERN_INODE
.br
.in +.5i
Return the entire inode table.
Note, the inode 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 inode
\fIstruct inode *\fP
followed by the inode itself
\fIstruct inode\fP.  There can never be more than \fBKERN_MAXINODES\fP
inodes returned.
.sp
.in -.5i
KERN_TEXT
.br
.in +.5i
Return the entire text table.  The returned data consists of an array whose
size depends on the current number of such objects active in the system. 
Each element of the array contains the kernel address of a text
\fIstruct text *\fP followed by the text structure itself
\fIstruct text\fP.  There can never be more structures than returned
by \fBKERN_MAXTEXTS\fP.
.in -.5i
.SH CTL_MACHDEP
The set of variables defined is architecture dependent.
Most architectures define at least the following variables.
.nf
.sp
.ta .25i 2.75i 3.75i
	Second level name	Type	Changeable
	CPU_CONSDEV	dev_t	no
.fi
.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.
.nf
.sp
.ta .25i 2.25i 4.0i
	Second level name	Type	Changeable
	PF\_ROUTE	routing messages	no
	PF\_INET	internet values	yes
.fi
.PP
PF_ROUTE
.br
.in +.5i
Return the entire routing table or a subset of it.
The data is returned as a sequence of routing messages (see
\fIroute(4)\fP
for the header file, format and meaning).
The length of each message is contained in the message header.
.in -.5i
.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:
.nf
.sp
.ta .25i 2.75i
	Fifth level name	Sixth level is:
	NET\_RT\_FLAGS	rtflags
	NET\_RT\_DUMP	None
	NET\_RT\_IFLIST	None
.fi
.sp
PF_INET
.br
.in +.5i
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:
.sp
.in -.5i
.nf
.ta .25i 2.0i 3.75i 4.75i
	Protocol name	Variable name	Type	Changeable
	ip	forwarding	integer	yes
	ip	redirect	integer	yes
	ip	ttl	integer	yes
	icmp	maskrepl	integer	yes
	udp	checksum	integer	yes
.fi
.PP
The variables are as follows:
.sp
ip.forwarding
.br
.in +.5i
Returns 1 when IP forwarding is enabled for the host,
meaning that the host is acting as a router.
.sp
.in -.5i
ip.redirect
.br
.in +.5i
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.
.sp
.in -.5i
ip.ttl
.br
.in +.5i
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.
.sp
.in -.5i
icmp.maskrepl
.br
.in +.5i
Returns 1 if ICMP network mask requests are to be answered.
.sp
.in -.5i
udp.checksum
.br
.in +.5i
Returns 1 when UDP checksums are being computed and checked.
Disabling UDP checksums is strongly discouraged.
.sp
.in -.5i
.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.
.sp
.nf
.ta .25i 3.0i 4.25i
	Second level name	Type	Changeable
	USER\_BC\_BASE\_MAX	integer	no
	USER\_BC\_DIM\_MAX	integer	no
	USER\_BC\_SCALE\_MAX	integer	no
	USER\_BC\_STRING\_MAX	integer	no
	USER\_COLL\_WEIGHTS\_MAX	integer	no
	USER\_CS\_PATH	string	no
	USER\_EXPR\_NEST\_MAX	integer	no
	USER\_LINE\_MAX	integer	no
	USER\_POSIX2\_CHAR\_TERM	integer	no
	USER\_POSIX2\_C\_BIND	integer	no
	USER\_POSIX2\_C\_DEV	integer	no
	USER\_POSIX2\_FORT\_DEV	integer	no
	USER\_POSIX2\_FORT\_RUN	integer	no
	USER\_POSIX2\_LOCALEDEF	integer	no
	USER\_POSIX2\_SW\_DEV	integer	no
	USER\_POSIX2\_UPE	integer	no
	USER\_POSIX2\_VERSION	integer	no
	USER\_RE\_DUP\_MAX	integer	no
	USER\_STREAM\_MAX	integer	no
	USER\_TZNAME\_MAX	integer	no
.fi
.PP
USER_BC_BASE_MAX
.br
.in +.5i
The maximum ibase/obase values in the
\fIbc(1)\fP
utility.
.sp
.in -.5i
USER_BC_DIM_MAX
.br
.in +.5i
The maximum array size in the
\fIbc(1)\fP
utility.
.sp
.in -.5i
USER_BC_SCALE_MAX
.br
.in +.5i
The maximum scale value in the
\fIbc(1)\fP
utility.
.sp
.in -.5i
USER_BC_STRING_MAX
.br
.in +.5i
The maximum string length in the
\fIbc(1)\fP
utility.
.sp
.in -.5i
USER_COLL_WEIGHTS_MAX
.br
.in +.5i
The maximum number of weights that can be assigned to any entry of
the LC_COLLATE order keyword in the locale definition file.
.sp
.in -.5i
USER_CS_PATH
.br
.in +.5i
Return a value for the
\fIPATH\fP
environment variable that finds all the standard utilities.
.sp
.in -.5i
USER_EXPR_NEST_MAX
.br
.in +.5i
The maximum number of expressions that can be nested within
parenthesis by the
\fIexpr(1)\fP
utility.
.sp
.in -.5i
USER_LINE_MAX
.br
.in +.5i
The maximum length in bytes of a text-processing utility's input
line.
.sp
.in -.5i
USER_POSIX2_CHAR_TERM
.br
.in +.5i
Return 1 if the system supports at least one terminal type capable of
all operations described in POSIX 1003.2, otherwise 0.
.sp
.in -.5i
USER_POSIX2_C_BIND
.br
.in +.5i
Return 1 if the system's C-language development facilities support the
C-Language Bindings Option, otherwise 0.
.sp
.in -.5i
USER_POSIX2_C_DEV
.br
.in +.5i
Return 1 if the system supports the C-Language Development Utilities Option,
otherwise 0.
.sp
.in -.5i
USER_POSIX2_FORT_DEV
.br
.in +.5i
Return 1 if the system supports the FORTRAN Development Utilities Option,
otherwise 0.
.sp
.in -.5i
USER_POSIX2_FORT_RUN
.br
.in +.5i
Return 1 if the system supports the FORTRAN Runtime Utilities Option,
otherwise 0.
.sp
.in -.5i
USER_POSIX2_LOCALEDEF
.br
.in +.5i
Return 1 if the system supports the creation of locales, otherwise 0.
.sp
.in -.5i
USER_POSIX2_SW_DEV
.br
.in +.5i
Return 1 if the system supports the Software Development Utilities Option,
otherwise 0.
.sp
.in -.5i
USER_POSIX2_UPE
.br
.in +.5i
Return 1 if the system supports the User Portability Utilities Option,
otherwise 0.
.sp
.in -.5i
USER_POSIX2_VERSION
.br
.in +.5i
The version of POSIX 1003.2 with which the system attempts to comply.
.sp
.in -.5i
USER_RE_DUP_MAX
.br
.in +.5i
The maximum number of repeated occurrences of a regular expression
permitted when using interval notation.
.sp
.in -.5i
USER_STREAM_MAX
.br
.in +.5i
The minimum maximum number of streams that a process may have open
at any one time.
.sp
.in -.5i
USER_TZNAME_MAX
.br
.in +.5i
The minimum maximum number of types supported for the name of a
timezone.
.br
.in -.5i
.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.
.sp
.nf
.ta .25i 2.25i 4.0i
	Second level name	Type	Changeable
	VM\_LOADAVG	struct loadavg	no
	VM\_METER	struct vmtotal	no
	VM\_SWAPMAP	struct map	no
	VM\_COREMAP	struct map	no
.fi
.PP
VM_LOADAVG
.br
.in +.5i
Return the load average history.
The returned data consists of a
\fIstruct loadavg\fP.
.sp
.in -.5i
VM_METER
.br
.in +.5i
Return the system wide virtual memory statistics.
The returned data consists of a
\fIstruct vmtotal\fP.
.br
.in -.5i
.sp
VM_SWAPMAP
.br
.in +.5i
Return the swapmap.  The size of this structure is fixed and may be
determined by specifying a \fBoldlenp\fP initialized to zero, the kernel
will fill in the size of the swapmap.
.in -.5i
.sp
VM_COREMAP
.br
.in +.5i
Same as for swapmap above except that the core allocation map is
returned.
.in -.5i
.SH RETURN VALUES
If the call to
\fBsysctl\fP
is successful, 0 is returned.
Otherwise \-1 is returned and
\fIerrno\fP
is set appropriately.
.SH ERRORS
The following errors may be reported:
.TP 15
EFAULT
The buffer
\fIname\fP,
\fIoldp\fP ,
\fInewp\fP ,
or length pointer
\fIoldlenp\fP
contains an invalid address.
.TP 15
EINVAL
The
\fIname\fP
array is less than two or greater than CTL_MAXNAME.
.TP 15
EINVAL
A non-null
\fInewp\fP
is given and its specified length in
\fInewlen\fP
is too large or too small.
.TP 15
ENOMEM
The length pointed to by
\fIoldlenp\fP
is too short to hold the requested value.
.TP 15
ENOTDIR
The
\fIname\fP
array specifies an intermediate rather than terminal name.
.TP 15
EOPNOTSUPP
The
\fIname\fP
array specifies a value that is unknown.
.TP 15
EPERM
An attempt is made to set a read-only value.
.TP 15
EPERM
A process without appropriate privilege attempts to set a value.
.SH FILES
.TP 15
<sys/sysctl.h>
definitions for top level identifiers, second level kernel and hardware
identifiers, and user level identifiers
.TP 15
<sys/socket.h>
definitions for second level network identifiers
.TP 15
<sys/gmon.h>
definitions for third level profiling identifiers
.TP 15
<sys/vmparam.h>
definitions for second level virtual memory identifiers
.TP 15
<netinet/in.h>
definitions for third level Internet identifiers and
fourth level IP identifiers
.TP 15
<netinet/icmp_var.h>
definitions for fourth level ICMP identifiers
.TP 15
<netinet/udp_var.h>
definitions for fourth level UDP identifiers
.SH SEE ALSO
.I sysctl(8)
.SH HISTORY
The
.B sysctl
function first appeared in 4.4BSD.
.PP
The KERN_TEXT, KERN_MAXTEXTS, VM_SWAPMAP, VM_COREMAP options are
2.11BSD specific extensions to the 4.4BSD \fIsysctl\fP implmentation.
.PP
Having KERN_FILE return the address of the file structure before the
actual \fIstruct file\fP is a 2.11BSD enhancement.  The \fIinode\fP
(\fIvnode\fP under 4.4) table was handled this way.