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Diff for /src/lib/libc/gen/sysctl.3 between version 1.24 and 1.25

version 1.24, 1998/04/13 21:24:49

version 1.25, 1998/04/28 20:11:35

Line 48

.Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"

.Sh DESCRIPTION

The

.Nm sysctl

.Nm

function retrieves system information and allows processes with

appropriate privileges to set system information.

The information available from

.Nm sysctl

.Nm

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,

.Nm sysctl

.Nm

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

.Nm sysctl

.Nm

are serialized to avoid deadlock.

.Pp

The state is described using a ``Management Information Base'' (MIB)

Line 91 and

.Fa oldlenp

should be set to NULL.

.Pp

The size of the available data can be determined by calling

.Nm sysctl

.Nm

with a NULL parameter for

.Fa oldp .

The size of the available data will be returned in the location pointed to by

Line 158 sysctl(mib, 2, p, &len, NULL, 0);

.Sh CTL_DEBUG

The debugging variables vary from system to system.

A debugging variable may be added or deleted without need to recompile

.Nm sysctl

.Nm

to know about it.

Each time it runs,

.Nm sysctl

.Nm

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

.Dv debug0

through

.Nm debug19 .

.Dv 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

.Dv dospecialcheck

as a debugging variable, the following declaration would be used:

.Bd -literal -offset indent -compact

int dospecialcheck = 1;

Line 291 information.

.Bl -tag -width "123456"

.It Li KERN_ARGMAX

The maximum bytes of argument to

.Xr exec 2 .

.Xr execve 2 .

.It Li KERN_AUTONICETIME

The number of seconds of cpu-time a non-root process may accumulate before

having its priority lowered from the default to the value of KERN_AUTONICEVAL.

Line 387 Return profiling information about the k

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.

Line 719 DDB. See

for more details.

.Sh RETURN VALUES

If the call to

.Nm sysctl

.Nm

is successful, the number of bytes copied out is returned.

Otherwise \-1 is returned and

.Va errno

Line 790 definitions for fourth level UDP identif

.Xr sysctl 8

.Sh HISTORY

The

.Nm sysctl

.Nm

function first appeared in

.Bx 4.4 .

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