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sysctl(8) [osx man page]

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

sysctl -- get or set kernel state SYNOPSIS
sysctl [-bn] name ... sysctl [-bn] -w name=value ... sysctl [-bn] -a sysctl [-bn] -A sysctl [-bn] -X 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 following options are available: -A List all MIB variables including opaque variables (which are normally suppressed). The format and length are printed, as well as a hex dump of the first sixteen bytes of the value. -a List all the currently available non-opaque values. This option is ignored if one or more variable names are specified on the com- mand line. -b Force the value of the variable(s) to be output in raw, binary format. No names are printed and no terminating newlines are output. This is mostly useful with a single variable. -n Show only variable values, not their names. This option is useful for setting shell variables. For instance, to save the pagesize in variable psize, use: set psize=`sysctl -n hw.pagesize` -w name=value Used to set values. The MIB name ( name ) followed by an equal sign and the new value ( value ) to be used. -X Same as -A, but prints a hex dump of the entire value instead of just the first few bytes. If just a MIB style name is given, the corresponding value is retrieved. 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 summarized 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 vm.swapusage 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.memsize 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 The sysctl program can get or set debugging variables that have been identified for its display. This information can be obtained by using the command: sysctl debug In addition, sysctl can extract information about the filesystems that have been compiled into the running system. This information can be obtained by using the command: sysctl vfs By default, only filesystems that are actively being used are listed. Use of the -A flag lists all the filesystems compiled into the running kernel. EXAMPLES
For example, to retrieve the maximum number of processes allowed in the system, one would use the request: sysctl kern.maxproc To set the maximum number of processes allowed in the system to 1000, one would use the 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 Information about the system's swap space usage may be obtained with: sysctl vm.swapusage 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 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. BSD
June 2, 2019 BSD
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