int i, mib[4]; 
size_t len; 
struct kinfo_proc kp; 
 
/* Fill out the first three components of the mib */ 
len = 4; 
sysctlnametomib("kern.proc.pid", mib, &len); 
 
/* Fetch and print entries for pid's < 100 */ 
for (i = 0; i < 100; i++) { 
 mib[3] = i; 
 len = sizeof(kp); 
 if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1) 
  perror("sysctl"); 
 else if (len > 0) 
  printkproc(&kp); 
}

int mib[2], maxproc; 
size_t len; 
 
mib[0] = CTL_KERN; 
mib[1] = KERN_MAXPROC; 
len = sizeof(maxproc); 
sysctl(mib, 2, &maxproc, &len, NULL, 0);

int mib[2]; 
size_t len; 
char *p; 
 
mib[0] = CTL_USER; 
mib[1] = USER_CS_PATH; 
sysctl(mib, 2, NULL, &len, NULL, 0); 
p = malloc(len); 
sysctl(mib, 2, p, &len, NULL, 0);

CTL_DEBUG

The debugging variables vary from system to system. A debugging variable may be added or deleted without need to recompile sysctl() to know about it. Each time it runs, sysctl() gets the list of debugging variables from the kernel and displays their current values. The system defines twenty ( struct ctldebug) variables named debug0 through debug19. They are declared as separate variables so that they can be individually initialized at the location of their associated variable. The loader prevents multiple use of the same variable by issuing errors if a variable is initialized in more than one place. For example, to export the variable dospecialcheck as a debugging variable, the following declaration would be used:

int dospecialcheck = 1; 
struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };

CTL_VFS

A distinguished second level name, VFS_GENERIC, is used to get general information about all file systems. One of its third level identifiers is VFS_MAXTYPENUM that gives the highest valid file system type number. Its other third level identifier is VFS_CONF that returns configuration information about the file system type given as a fourth level identifier (see getvfsbyname(3) as an example of its use). The remaining second level identifiers are the file system type number returned by a statfs(2) call or from VFS_CONF. The third level identifiers available for each file system are given in the header file that defines the mount argument structure for that file system.

CTL_HW

The string and integer information available for the CTL_HW level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value.

Second level name	Type	Changeable
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
HW_FLOATINGPT	integer	no
HW_MACHINE_ARCH	string	no
HW_REALMEM	integer	no

HW_MACHINE

The machine class.

HW_MODEL

The machine model

HW_NCPU

The number of cpus.

HW_BYTEORDER

The byteorder (4,321, or 1,234).

HW_PHYSMEM

The bytes of physical memory.

HW_USERMEM

The bytes of non-kernel memory.

HW_PAGESIZE

The software page size.

HW_FLOATINGPT

Nonzero if the floating point support is in hardware.

HW_MACHINE_ARCH

The machine dependent architecture type.

HW_REALMEM

The bytes of real memory.

CTL_KERN

The string and integer information available for the CTL_KERN level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. The types of data currently available are process information, system vnodes, the open file entries, routing table entries, virtual memory statistics, load average history, and clock rate information.

Second level name	Type	Changeable
KERN_ARGMAX	integer	no
KERN_BOOTFILE	string	yes
KERN_BOOTTIME	struct timeval	no
KERN_CLOCKRATE	struct clockinfo	no
KERN_FILE	struct xfile	no
KERN_HOSTID	integer	yes
KERN_HOSTUUID	string	yes
KERN_HOSTNAME	string	yes
KERN_JOB_CONTROL	integer	no
KERN_MAXFILES	integer	yes
KERN_MAXFILESPERPROC	integer	yes
KERN_MAXPROC	integer	no
KERN_MAXPROCPERUID	integer	yes
KERN_MAXVNODES	integer	yes
KERN_NGROUPS	integer	no
KERN_NISDOMAINNAME	string	yes
KERN_OSRELDATE	integer	no
KERN_OSRELEASE	string	no
KERN_OSREV	integer	no
KERN_OSTYPE	string	no
KERN_POSIX1	integer	no
KERN_PROC	node	not applicable
KERN_PROF	node	not applicable
KERN_QUANTUM	integer	yes
KERN_SAVED_IDS	integer	no
KERN_SECURELVL	integer	raise only
KERN_UPDATEINTERVAL	integer	no
KERN_VERSION	string	no
KERN_VNODE	struct xvnode	no

KERN_ARGMAX

The maximum bytes of argument to execve(2).

KERN_BOOTFILE

The full pathname of the file from which the kernel was loaded.

KERN_BOOTTIME

A struct timeval structure is returned. This structure contains the time that the system was booted.

KERN_CLOCKRATE

A struct clockinfo structure is returned. This structure contains the clock, statistics clock and profiling clock frequencies, the number of micro-seconds per hz tick and the skew rate.

KERN_FILE

Return the entire file table. The returned data consists of an array of struct xfile, whose size depends on the current number of such objects in the system.

KERN_HOSTID

Get or set the host ID.

KERN_HOSTUUID

Get or set the host's universally unique identifier (UUID).

KERN_HOSTNAME

Get or set the hostname.

KERN_JOB_CONTROL

Return 1 if job control is available on this system, otherwise 0.

KERN_MAXFILES

The maximum number of files that may be open in the system.

KERN_MAXFILESPERPROC

The maximum number of files that may be open for a single process. This limit only applies to processes with an effective uid of nonzero at the time of the open request. Files that have already been opened are not affected if the limit or the effective uid is changed.

KERN_MAXPROC

The maximum number of concurrent processes the system will allow.

KERN_MAXPROCPERUID

The maximum number of concurrent processes the system will allow for a single effective uid. This limit only applies to processes with an effective uid of nonzero at the time of a fork request. Processes that have already been started are not affected if the limit is changed.

KERN_MAXVNODES

The maximum number of vnodes available on the system.

KERN_NGROUPS

The maximum number of supplemental groups.

KERN_NISDOMAINNAME

The name of the current YP/NIS domain.

KERN_OSRELDATE

The kernel release version in the format M mm R xx, where M is the major version, mm is the two digit minor version, R is 0 if release branch, otherwise 1, and xx is updated when the available APIs change.

The userland release version is available from < osreldate.h>; parse this file if you need to get the release version of the currently installed userland.

KERN_OSRELEASE

The system release string.

KERN_OSREV

The system revision string.

KERN_OSTYPE

The system type string.

KERN_POSIX1

The version of IEEE Std 1003.1 (“POSIX.1”) with which the system attempts to comply.

KERN_PROC

Return selected information about specific running processes.

For the following names, an array of struct kinfo_proc structures is returned, whose size depends on the current number of such objects in the system.

Third level name	Fourth level is:
KERN_PROC_ALL	None
KERN_PROC_PID	A process ID
KERN_PROC_PGRP	A process group
KERN_PROC_TTY	A tty device
KERN_PROC_UID	A user ID
KERN_PROC_RUID	A real user ID

If the third level name is KERN_PROC_ARGS then the command line argument array is returned in a flattened form, i.e., zero-terminated arguments follow each other. The total size of array is returned. It is also possible for a process to set its own process title this way. If the third level name is KERN_PROC_PATHNAME, the path of the process' text file is stored. For KERN_PROC_PATHNAME, a process ID of -1 implies the current process.

Third level name	Fourth level is:
KERN_PROC_ARGS	A process ID
KERN_PROC_PATHNAME	A process ID

KERN_PROF

Return profiling information about the kernel. If the kernel is not compiled for profiling, attempts to retrieve any of the KERN_PROF values will fail with ENOENT. The third level names for the string and integer profiling information is detailed below. The changeable column shows whether a process with appropriate privilege may change the value.

Third level name	Type	Changeable
GPROF_STATE	integer	yes
GPROF_COUNT	u_short[]	yes
GPROF_FROMS	u_short[]	yes
GPROF_TOS	struct tostruct	yes
GPROF_GMONPARAM	struct gmonparam	no

The variables are as follows:

GPROF_STATE

Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling is running or stopped.

GPROF_COUNT

Array of statistical program counter counts.

GPROF_FROMS

Array indexed by program counter of call-from points.

GPROF_TOS

Array of struct tostruct describing destination of calls and their counts.

GPROF_GMONPARAM

Structure giving the sizes of the above arrays.

KERN_QUANTUM

The maximum period of time, in microseconds, for which a process is allowed to run without being preempted if other processes are in the run queue.

KERN_SAVED_IDS

Returns 1 if saved set-group and saved set-user ID is available.

KERN_SECURELVL

The system security level. This level may be raised by processes with appropriate privilege. It may not be lowered.

KERN_VERSION

The system version string.

KERN_VNODE

Return the entire vnode table. Note, the vnode table is not necessarily a consistent snapshot of the system. The returned data consists of an array whose size depends on the current number of such objects in the system. Each element of the array consists of a struct xvnode.

CTL_NET

The string and integer information available for the CTL_NET level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value.

Second level name	Type	Changeable
PF_ROUTE	routing messages	no
PF_INET	IPv4 values	yes
PF_INET6	IPv6 values	yes

PF_ROUTE

Return the entire routing table or a subset of it. The data is returned as a sequence of routing messages (see route(4) for the header file, format and meaning). The length of each message is contained in the message header.

The third level name is a protocol number, which is currently always 0. The fourth level name is an address family, which may be set to 0 to select all address families. The fifth, sixth, and seventh level names are as follows:

Fifth level Sixth level	Seventh level
NET_RT_FLAGS rtflags	None
NET_RT_DUMP None	None or fib number
NET_RT_IFLIST 0 or if_index	None
NET_RT_IFMALIST 0 or if_index	None
NET_RT_IFLISTL 0 or if_index	None

The NET_RT_IFMALIST name returns information about multicast group memberships on all interfaces if 0 is specified, or for the interface specified by if_index.

The NET_RT_IFLISTL is like NET_RT_IFLIST, just returning message header structs with additional fields allowing the interface to be extended without breaking binary compatibility. The NET_RT_IFLISTL uses 'l' versions of the message header structures: struct if_msghdrl and struct ifa_msghdrl.

PF_INET

Get or set various global information about the IPv4 (Internet Protocol version 4). The third level name is the protocol. The fourth level name is the variable name. The currently defined protocols and names are:

Protocol	Variable	Type	Changeable
icmp	bmcastecho	integer	yes
icmp	maskrepl	integer	yes
ip	forwarding	integer	yes
ip	redirect	integer	yes
ip	ttl	integer	yes
udp	checksum	integer	yes

The variables are as follows:

icmp.bmcastecho

Returns 1 if an ICMP echo request to a broadcast or multicast address is to be answered.

icmp.maskrepl

Returns 1 if ICMP network mask requests are to be answered.

ip.forwarding

Returns 1 when IP forwarding is enabled for the host, meaning that the host is acting as a router.

ip.redirect

Returns 1 when ICMP redirects may be sent by the host. This option is ignored unless the host is routing IP packets, and should normally be enabled on all systems.

ip.ttl

The maximum time-to-live (hop count) value for an IP packet sourced by the system. This value applies to normal transport protocols, not to ICMP.

udp.checksum

Returns 1 when UDP checksums are being computed and checked. Disabling UDP checksums is strongly discouraged.

For variables net.inet.*.ipsec, please refer to ipsec(4).

PF_INET6

Get or set various global information about the IPv6 (Internet Protocol version 6). The third level name is the protocol. The fourth level name is the variable name.

For variables net.inet6.* please refer to inet6(4). For variables net.inet6.*.ipsec6, please refer to ipsec(4).

CTL_USER

The string and integer information available for the CTL_USER level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value.

Second level name	Type	Changeable
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_CS_PATH	string	no
USER_EXPR_NEST_MAX	integer	no
USER_LINE_MAX	integer	no
USER_POSIX2_CHAR_TERM	integer	no
USER_POSIX2_C_BIND	integer	no
USER_POSIX2_C_DEV	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
USER_POSIX2_VERSION	integer	no
USER_RE_DUP_MAX	integer	no
USER_STREAM_MAX	integer	no
USER_TZNAME_MAX	integer	no

USER_BC_BASE_MAX

The maximum ibase/obase values in the bc(1) utility.

USER_BC_DIM_MAX

The maximum array size in the bc(1) utility.

USER_BC_SCALE_MAX

The maximum scale value in the bc(1) utility.

USER_BC_STRING_MAX

The maximum string length in the bc(1) utility.

USER_COLL_WEIGHTS_MAX

The maximum number of weights that can be assigned to any entry of the LC_COLLATE order keyword in the locale definition file.

USER_CS_PATH

Return a value for the PATH environment variable that finds all the standard utilities.

USER_EXPR_NEST_MAX

The maximum number of expressions that can be nested within parenthesis by the expr(1) utility.

USER_LINE_MAX

The maximum length in bytes of a text-processing utility's input line.

USER_POSIX2_CHAR_TERM

Return 1 if the system supports at least one terminal type capable of all operations described in IEEE Std 1003.2 (“POSIX.2”), otherwise 0.

USER_POSIX2_C_BIND

Return 1 if the system's C-language development facilities support the C-Language Bindings Option, otherwise 0.

USER_POSIX2_C_DEV

Return 1 if the system supports the C-Language Development Utilities Option, otherwise 0.

USER_POSIX2_FORT_DEV

Return 1 if the system supports the FORTRAN Development Utilities Option, otherwise 0.

USER_POSIX2_FORT_RUN

Return 1 if the system supports the FORTRAN Runtime Utilities Option, otherwise 0.

USER_POSIX2_LOCALEDEF

Return 1 if the system supports the creation of locales, otherwise 0.

USER_POSIX2_SW_DEV

Return 1 if the system supports the Software Development Utilities Option, otherwise 0.

USER_POSIX2_UPE

Return 1 if the system supports the User Portability Utilities Option, otherwise 0.

USER_POSIX2_VERSION

The version of IEEE Std 1003.2 (“POSIX.2”) with which the system attempts to comply.

USER_RE_DUP_MAX

The maximum number of repeated occurrences of a regular expression permitted when using interval notation.

USER_STREAM_MAX

The minimum maximum number of streams that a process may have open at any one time.

USER_TZNAME_MAX

The minimum maximum number of types supported for the name of a timezone.

CTL_VM

The string and integer information available for the CTL_VM level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value.

Second level name	Type	Changeable
VM_LOADAVG	struct loadavg	no
VM_TOTAL	struct vmtotal	no
VM_SWAPPING_ENABLED	integer	maybe
VM_V_CACHE_MAX	integer	yes
VM_V_CACHE_MIN	integer	yes
VM_V_FREE_MIN	integer	yes
VM_V_FREE_RESERVED	integer	yes
VM_V_FREE_TARGET	integer	yes
VM_V_INACTIVE_TARGET	integer	yes
VM_V_PAGEOUT_FREE_MIN	integer	yes

VM_LOADAVG

Return the load average history. The returned data consists of a struct loadavg.

VM_TOTAL

Return the system wide virtual memory statistics. The returned data consists of a struct vmtotal.

VM_SWAPPING_ENABLED

1 if process swapping is enabled or 0 if disabled. This variable is permanently set to 0 if the kernel was built with swapping disabled.

VM_V_CACHE_MAX

Maximum desired size of the cache queue.

VM_V_CACHE_MIN

Minimum desired size of the cache queue. If the cache queue size falls very far below this value, the pageout daemon is awakened.

VM_V_FREE_MIN

Minimum amount of memory (cache memory plus free memory) required to be available before a process waiting on memory will be awakened.

VM_V_FREE_RESERVED

Processes will awaken the pageout daemon and wait for memory if the number of free and cached pages drops below this value.

VM_V_FREE_TARGET

The total amount of free memory (including cache memory) that the pageout daemon tries to maintain.

VM_V_INACTIVE_TARGET

The desired number of inactive pages that the pageout daemon should achieve when it runs. Inactive pages can be quickly inserted into process address space when needed.

VM_V_PAGEOUT_FREE_MIN

If the amount of free and cache memory falls below this value, the pageout daemon will enter "memory conserving mode" to avoid deadlock.