SYSCTL(8) MachTen System Manager’s Manual SYSCTL(8)

NAME
sysctl - get or set kernel state

SYNOPSIS
sysctl [-n] name ...
sysctl [-n] -w name=value ...
sysctl [-n] -aA

DESCRIPTION
The sysctl utility retrieves kernel state and allows processes with ap-
propriate privilege to set kernel state. The state to be retrieved or
set is described using a ‘‘Management Information Base’’ (‘‘MIB’’) style
name, described as a dotted set of components. The -a flag can be used
to list all the currently available string or integer values. The -A
flag will list all the known MIB names including tables. Those with
string or integer values will be printed as with the -a flag; for the
table values, the name of the utility to retrieve them is given.

The -n flag specifies that the printing of the field name should be sup-
pressed and that only its value should be output. This flag is useful
for setting shell variables. For example, to save the pagesize in vari-
able psize, use:
set psize=‘sysctl -n hw.pagesize‘

If just a MIB style name is given, the corresponding value is retrieved.
If a value is to be set, the -w flag must be specified and the MIB name
followed by an equal sign and the new value to be used.

The information available from sysctl consists of integers, strings, and
tables. The tabular information can only be retrieved by special purpose
programs such as ps, systat, and netstat. The string and integer informa-
tion is summaried below. For a detailed description of these variable
see sysctl(3). The changeable column indicates whether a process with
appropriate privilege can change the value.

Name Type Changeable
kern.ostype string no
kern.osrelease string no
kern.osrevision integer no
kern.version string no
kern.maxvnodes integer yes
kern.maxproc integer yes
kern.maxfiles integer yes
kern.argmax integer no
kern.securelevel integer raise only
kern.hostname string yes
kern.hostid integer yes
kern.clockrate struct no
kern.posix1version integer no
kern.ngroups integer no
kern.job_control integer no
kern.saved_ids integer no
kern.link_max integer no
kern.max_canon integer no
kern.max_input integer no
kern.name_max integer no
kern.path_max integer no
kern.pipe_buf integer no
kern.chown_restricted integer no
kern.no_trunc integer no

kern.vdisable integer no
kern.boottime struct no
vm.loadavg struct no
machdep.console_device dev_t no
net.inet.ip.forwarding integer yes
net.inet.ip.redirect integer yes
net.inet.ip.ttl integer yes
net.inet.icmp.maskrepl integer yes
net.inet.udp.checksum integer yes
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
user.cs_path string no
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.expr_nest_max integer no
user.line_max integer no
user.re_dup_max integer no
user.posix2_version integer no
user.posix2_c_bind integer no
user.posix2_c_dev integer no
user.posix2_char_term 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

EXAMPLES
For example, to retrieve the maximum number of processes allowed in the
system, one would use the follow request:
sysctl kern.maxproc

To set the maximum number of processes allowed in the system to 1000, one
would use the follow request:
sysctl -w kern.maxproc=1000

Information about the system clock rate may be obtained with:
sysctl kern.clockrate

Information about the load average history may be obtained with
sysctl vm.loadavg

FILES
<sys/sysctl.h> definitions for top level identifiers, second level
kernel and hardware identifiers, and user level
identifiers
<sys/socket.h> definitions for second level network identifiers
<sys/gmon.h> definitions for third level profiling identifiers
<vm/vm_param.h> definitions for second level virtual memory identi-
fiers
<netinet/in.h> definitions for third level Internet identifiers
and fourth level IP identifiers
<netinet/icmp_var.h> definitions for fourth level ICMP identifiers
<netinet/udp_var.h> definitions for fourth level UDP identifiers