Mac OS X for Unix Geeks

sysctl

sysctl is a standard BSD facility for configuring kernel state variables. Use sysctl name to display a variable name, as in sysctl kern.ostype. Use sysctl -a to display all variables. You can set a variable with sysctl -w name = value. You must have superuser privileges to set a variable.

Table 8-6 lists the sysctl variables on Mac OS X. See the sysctl(3) manpage for a description of the sysctl system call and more detailed information on the kernel state variables.

Table 8-6. sysctl’s kernel state variables

Name	Type	Writable	Description
hw.busfrequency	int	no	Bus frequency in hertz. Divide by one million to get a megahertz figure.
hw.byteorder	int	no	Variable that returns 4321, showing the ordering of four bytes on the PowerPC platform.
hw.cachelinesize	int	no	The cache line size in bytes.
hw.cpufrequency	int	no	CPU frequency in hertz. Divide by one million to get a megahertz figure.
hw.epoch	int	no	Variable that indicates whether your hardware is in the New World or the Old World. Old World Macintoshes (pre-G3) will have a value of 0.
hw.l1dcachesize	int	no	Level 1 data cache size in bytes.
hw.l1icachesize	int	no	Level 1 instruction cache size in bytes.
hw.l2cachesize	int	no	Level 2 cache size in bytes.
hw.l2settings	int	no	Level 2 cache settings.
hw.l3cachesize	int	no	Level 3 cache size in bytes.
hw.l3settings	int	no	Level 3 cache settings.
hw.machine	string	no	Machine class (Power Macintosh ...