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sysctl(8) [bsd man page]

SYSCTL(8)						      System Manager's Manual							 SYSCTL(8)

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 appropriate 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 suppressed and that only its value should be output. This flag is use- ful for setting shell variables. For example, to save the pagesize in variable 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 information 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 long no kern.version string no kern.maxinodes integer no kern.maxproc integer no kern.maxfiles integer no kern.maxtext integer no kern.argmax integer no kern.securelevel integer raise only kern.hostname string yes kern.hostid long yes kern.clockrate struct no kern.posix1version integer no kern.ngroups integer no kern.job_control integer no kern.saved_ids 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 long no hw.usermem long 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 hostname of the system to, one would use the follow request: sysctl -w 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 <sys/vmparam.h> definitions for second level virtual memory identifiers <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 SEE ALSO
sysctl(3) HISTORY
sysctl first appeared in 4.4BSD. 4th Berkeley Distribution June 6, 1993 SYSCTL(8)
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