SYSCTL(8)						      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 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 foo.bar.com, one would use the follow request:

		 sysctl -w kern.hostname=foo.bar.com

       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)