NAME
ssyyssccttll, ssyyssccttllbbyynnaammee, ssyyssccttllnnaammeettoommiibb - get or set system information
LLIIBBRRAARRYYStandard C Library (libc, -lc)
SYNOPSIS
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int ssyyssccttll(int *name, uint namelen, void *oldp, sizet *oldlenp, void *newp, sizet newlen); int ssyyssccttllbbyynnaammee(const char *name, void *oldp, sizet *oldlenp, void *newp, sizet newlen); int ssyyssccttllnnaammeettoommiibb(const char *name, int *mibp, sizet *sizep);> DESCRIPTION
The ssyyssccttll() function retrieves system information and allows processes with appropriate privileges to set system information. The information available from ssyyssccttll() consists of integers, strings, and tables. Information may be retrieved and set from the command interface using the sysctl(8) utility. Unless explicitly noted below, ssyyssccttll() returns a consistent snapshot of the data requested. Consistency is obtained by locking the destination buffer into memory so that the data may be copied out without blocking. Calls to ssyyssccttll() are serialized to avoid deadlock. The state is described using a ``Management Information Base'' (MIB) style name, listed in name, which is a namelen length array of integers. The ssyyssccttllbbyynnaammee() function accepts an ASCII representation of the name and internally looks up the integer name vector. Apart from that, it behaves the same as the standard ssyyssccttll() function. The information is copied into the buffer specified by oldp. The size of the buffer is given by the location specified by oldlenp before the call, and that location gives the amount of data copied after a successful call and after a call that returns with the error code ENOMEM. If the amount of data available is greater than the size of the buffer supplied, the call supplies as much data as fits in the buffer provided and returns with the error code ENOMEM. If the old value is not desired, oldp and oldlenp should be set to NULL. The size of the available data can be determined by calling ssyyssccttll() with the NULL argument for oldp. The size of the available data will be returned in the location pointed to by oldlenp. For some operations, the amount of space may change often. For these operations, the system attempts to round up so that the returned size is large enough for a call to return the data shortly thereafter. To set a new value, newp is set to point to a buffer of length newlen from which the requested value is to be taken. If a new value is not to be set, newp should be set to NULL and newlen set to 0. The ssyyssccttllnnaammeettoommiibb() function accepts an ASCII representation of thename, looks up the integer name vector, and returns the numeric represen-
tation in the mib array pointed to by mibp. The number of elements in the mib array is given by the location specified by sizep before thecall, and that location gives the number of entries copied after a suc-
cessful call. The resulting mib and size may be used in subsequent ssyyssccttll() calls to get the data associated with the requested ASCII name.This interface is intended for use by applications that want to repeat-
edly request the same variable (the ssyyssccttll() function runs in about a third the time as the same request made via the ssyyssccttllbbyynnaammee() function). The ssyyssccttllnnaammeettoommiibb() function is also useful for fetching mib prefixesand then adding a final component. For example, to fetch process infor-
mation for processes with pid's less than 100: int i, mib[4]; sizet len; struct kinfoproc 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); }Note: Implementation of pprriinnttkkpprroocc() - to print whatever data deemed
necessary from the large kinfoproc structure (
as an exercise for the reader. The top level names are defined with a CTL prefix in) - is left , and are as follows. The next and subsequent levels down are found in the include files listed here, and described in separate sections below. NNaammee NNeexxtt lleevveell nnaammeess DDeessccrriippttiioonn CTLDEBUG sys/sysctl.h Debugging CTLVFS sys/mount.h File system CTLHW sys/sysctl.h Generic CPU, I/O CTLKERN sys/sysctl.h High kernel limits CTLMACHDEP sys/sysctl.h Machine dependent CTLNET sys/socket.h Networking CTLUSER sys/sysctl.h User-level
CTLVM sys/resources.h Virtual memory (struct loadavg) CTLVM sys/vmmeter.h Virtual memory (struct vmtotal) For example, the following retrieves the maximum number of processes allowed in the system: int mib[2], maxproc; sizet len; mib[0] = CTLKERN; mib[1] = KERNMAXPROC; len = sizeof(maxproc); sysctl(mib, 2, &maxproc, &len, NULL, 0); To retrieve the standard search path for the system utilities: int mib[2]; sizet len; char *p; mib[0] = CTLUSER; mib[1] = USERCSPATH; sysctl(mib, 2, NULL, &len, NULL, 0); p = malloc(len); sysctl(mib, 2, p, &len, NULL, 0); CCTTLLDDEEBBUUGG The debugging variables vary from system to system. A debugging variable may be added or deleted without need to recompile ssyyssccttll() to know about it. Each time it runs, ssyyssccttll() 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. Theyare declared as separate variables so that they can be individually ini-
tialized at the location of their associated variable. The loader pre-
vents multiple use of the same variable by issuing errors if a variableis initialized in more than one place. For example, to export the vari-
able dospecialcheck as a debugging variable, the following declaration would be used: int dospecialcheck = 1; struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; CCTTLLVVFFSS A distinguished second level name, VFSGENERIC, is used to get general information about all file systems. One of its third level identifiers is VFSMAXTYPENUM that gives the highest valid file system type number. Its other third level identifier is VFSCONF 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 VFSCONF. 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. CCTTLLHHWW The string and integer information available for the CTLHW level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. SSeeccoonndd lleevveell nnaammee TTyyppee CChhaannggeeaabbllee HWMACHINE string no HWMODEL string no HWNCPU integer no HWBYTEORDER integer no HWPHYSMEM integer no HWUSERMEM integer no HWPAGESIZE integer no HWFLOATINGPOINT integer no HWMACHINEARCH string no HWMACHINE The machine class. HWMODEL The machine model HWNCPU The number of cpus. HWBYTEORDER The byteorder (4,321, or 1,234). HWPHYSMEM The bytes of physical memory. HWUSERMEMThe bytes of non-kernel memory.
HWPAGESIZE The software page size. HWFLOATINGPOINT Nonzero if the floating point support is in hardware. HWMACHINEARCH The machine dependent architecture type. CCTTLLKKEERRNN The string and integer information available for the CTLKERN 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. SSeeccoonndd lleevveell nnaammee TTyyppee CChhaannggeeaabbllee KERNARGMAX integer no KERNBOOTFILE string yes KERNBOOTTIME struct timeval no KERNCLOCKRATE struct clockinfo no KERNFILE struct file no KERNHOSTID integer yesKERNHOSTNAME string yes
KERNJOBCONTROL integer no KERNMAXFILES integer yes KERNMAXFILESPERPROC integer yes KERNMAXPROC integer no KERNMAXPROCPERUID integer yes KERNMAXVNODES integer yes KERNNGROUPS integer noKERNNISDOMAINNAME string yes
KERNOSRELDATE integer no KERNOSRELEASE string no KERNOSREV integer no KERNOSTYPE string no KERNPOSIX1 integer no KERNPROC struct proc no KERNPROF node not applicable KERNQUANTUM integer yes KERNSAVEDIDS integer no KERNSECURELVL integer raise only KERNUPDATEINTERVAL integer no KERNVERSION string no KERNVNODE struct vnode no KERNARGMAX The maximum bytes of argument to execve(2). KERNBOOTFILE The full pathname of the file from which the kernel was loaded. KERNBOOTTIME A struct timeval structure is returned. This structure contains the time that the system was booted. KERNCLOCKRATEA struct clockinfo structure is returned. This structure con-
tains the clock, statistics clock and profiling clock frequen-
cies, the number of micro-seconds per hz tick and the skew rate.
KERNFILE Return the entire file table. The returned data consists of a single struct filehead followed by an array of struct file, whose size depends on the current number of such objects in the system. KERNHOSTID Get or set the host id.KERNHOSTNAME
Get or set the hostname. KERNJOBCONTROL Return 1 if job control is available on this system, otherwise 0. KERNMAXFILES The maximum number of files that may be open in the system. KERNMAXFILESPERPROC 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 havealready been opened are not affected if the limit or the effec-
tive uid is changed. KERNMAXPROC The maximum number of concurrent processes the system will allow. KERNMAXPROCPERUID 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. KERNMAXVNODES The maximum number of vnodes available on the system. KERNNGROUPS The maximum number of supplemental groups.KERNNISDOMAINNAME
The name of the current YP/NIS domain. KERNOSRELDATE The kernel release version in the format MmmRxx, 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; parse this file if you need to get the release version of the currently installed userland. KERNOSRELEASE The system release string. KERNOSREV The system revision string. KERNOSTYPE The system type string. KERNPOSIX1 The version of IEEE Std 1003.1 (``POSIX.1'') with which the sys-
tem attempts to comply. KERNPROC Return the entire process table, or a subset of it. An array of pairs of struct proc followed by corresponding struct eproc structures is returned, whose size depends on the current number of such objects in the system. The third and fourth level names are as follows: Third level name Fourth level is: KERNPROCALL None KERNPROCPID A process ID KERNPROCPGRP A process group KERNPROCTTY A tty device KERNPROCUID A user ID KERNPROCRUID A real user ID If the third level name is KERNPROCARGS then the command lineargument array is returned in a flattened form, i.e., zero-termi-
nated 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. TThhiirrdd lleevveell nnaammee FFoouurrtthh lleevveell iiss:: KERNPROCARGS A process ID KERNPROF Return profiling information about the kernel. If the kernel is not compiled for profiling, attempts to retrieve any of the KERNPROF values will fail with ENOENT. The third level names for the string and integer profiling information is detailedbelow. The changeable column shows whether a process with appro-
priate privilege may change the value. TThhiirrdd lleevveell nnaammee TTyyppee CChhaannggeeaabbllee GPROFSTATE integer yes GPROFCOUNT ushort[] yes GPROFFROMS ushort[] yes GPROFTOS struct tostruct yes GPROFGMONPARAM struct gmonparam no The variables are as follows: GPROFSTATEReturns GMONPROFON or GMONPROFOFF to show that pro-
filing is running or stopped. GPROFCOUNT Array of statistical program counter counts. GPROFFROMSArray indexed by program counter of call-from points.
GPROFTOS Array of struct tostruct describing destination of calls and their counts. GPROFGMONPARAM Structure giving the sizes of the above arrays. KERNQUANTUM 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. KERNSAVEDIDSReturns 1 if saved set-group and saved set-user ID is available.
KERNSECURELVL The system security level. This level may be raised by processes with appropriate privilege. It may not be lowered. KERNVERSION The system version string. KERNVNODEReturn the entire vnode table. Note, the vnode table is not nec-
essarily 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 contains the kernel address of a vnode struct vnode * followed by the vnode itself struct vnode. CCTTLLMMAACCHHDDEEPP The set of variables defined is architecture dependent. The following variables are defined for the i386 architecture. SSeeccoonndd lleevveell nnaammee TTyyppee CChhaannggeeaabbllee CPUCONSDEV devt no CPUADJKERNTZ int yes CPUDISRTCSET int yes CPUBOOTINFO struct bootinfo no CPUWALLCLOCK int yes CCTTLLNNEETT The string and integer information available for the CTLNET level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. SSeeccoonndd lleevveell nnaammee TTyyppee CChhaannggeeaabbllee PFROUTE routing messages no PFINET IPv4 values yes PFINET6 IPv6 values yes PFROUTE 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 and sixth level names are as follows: FFiifftthh lleevveell nnaammee SSiixxtthh lleevveell iiss:: NETRTFLAGS rtflags NETRTDUMP None NETRTIFLIST 0 or ifindex NETRTIFMALIST 0 or ifindex The NETRTIFMALIST name returns information about multicast group memberships on all interfaces if 0 is specified, or for the interface specified by ifindex. PFINET 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: PPrroottooccooll VVaarriiaabbllee TTyyppee CChhaannggeeaabbllee 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.bmcastechoReturns 1 if an ICMP echo request to a broadcast or mul-
ticast 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 nor-
mal transport protocols, not to ICMP. udp.checksum Returns 1 when UDP checksums are being computed andchecked. Disabling UDP checksums is strongly discour-
aged. For variables net.inet.*.ipsec, please refer to ipsec(4). PFINET6 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 vari-
ables net.inet6.*.ipsec6, please refer to ipsec(4). CCTTLLUUSSEERR The string and integer information available for the CTLUSER level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. SSeeccoonndd lleevveell nnaammee TTyyppee CChhaannggeeaabbllee USERBCBASEMAX integer no USERBCDIMMAX integer no USERBCSCALEMAX integer no USERBCSTRINGMAX integer no USERCOLLWEIGHTSMAX integer no USERCSPATH string no USEREXPRNESTMAX integer no USERLINEMAX integer no USERPOSIX2CHARTERM integer no USERPOSIX2CBIND integer no USERPOSIX2CDEV integer no USERPOSIX2FORTDEV integer no USERPOSIX2FORTRUN integer no USERPOSIX2LOCALEDEF integer no USERPOSIX2SWDEV integer no USERPOSIX2UPE integer no USERPOSIX2VERSION integer no USERREDUPMAX integer no USERSTREAMMAX integer noUSERTZNAMEMAX integer no
USERBCBASEMAX The maximum ibase/obase values in the bc(1) utility. USERBCDIMMAX The maximum array size in the bc(1) utility. USERBCSCALEMAX The maximum scale value in the bc(1) utility. USERBCSTRINGMAX The maximum string length in the bc(1) utility. USERCOLLWEIGHTSMAX The maximum number of weights that can be assigned to any entry of the LCCOLLATE order keyword in the locale definition file. USERCSPATH Return a value for the PATH environment variable that finds all the standard utilities. USEREXPRNESTMAX The maximum number of expressions that can be nested within parenthesis by the expr(1) utility. USERLINEMAXThe maximum length in bytes of a text-processing utility's input
line. USERPOSIX2CHARTERMReturn 1 if the system supports at least one terminal type capa-
ble of all operations described in IEEE Std 1003.2 (``POSIX.2''), otherwise 0. USERPOSIX2CBINDReturn 1 if the system's C-language development facilities sup-
port the C-Language Bindings Option, otherwise 0.
USERPOSIX2CDEVReturn 1 if the system supports the C-Language Development Utili-
ties Option, otherwise 0. USERPOSIX2FORTDEV Return 1 if the system supports the FORTRAN Development Utilities Option, otherwise 0. USERPOSIX2FORTRUN Return 1 if the system supports the FORTRAN Runtime Utilities Option, otherwise 0. USERPOSIX2LOCALEDEFReturn 1 if the system supports the creation of locales, other-
wise 0. USERPOSIX2SWDEVReturn 1 if the system supports the Software Development Utili-
ties Option, otherwise 0. USERPOSIX2UPE Return 1 if the system supports the User Portability Utilities Option, otherwise 0. USERPOSIX2VERSIONThe version of IEEE Std 1003.2 (``POSIX.2'') with which the sys-
tem attempts to comply. USERREDUPMAXThe maximum number of repeated occurrences of a regular expres-
sion permitted when using interval notation. USERSTREAMMAX The minimum maximum number of streams that a process may have open at any one time.USERTZNAMEMAX
The minimum maximum number of types supported for the name of a timezone. CCTTLLVVMM The string and integer information available for the CTLVM level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. SSeeccoonndd lleevveell nnaammee TTyyppee CChhaannggeeaabbllee VMLOADAVG struct loadavg no VMMETER struct vmtotal no VMPAGEOUTALGORITHM integer yes VMSWAPPINGENABLED integer maybe VMVCACHEMAX integer yes VMVCACHEMIN integer yes VMVFREEMIN integer yes VMVFREERESERVED integer yes VMVFREETARGET integer yes VMVINACTIVETARGET integer yes VMVPAGEOUTFREEMIN integer yes VMLOADAVG Return the load average history. The returned data consists of a struct loadavg. VMMETER Return the system wide virtual memory statistics. The returned data consists of a struct vmtotal. VMPAGEOUTALGORITHM0 if the statistics-based page management algorithm is in use or
1 if the near-LRU algorithm is in use.
VMSWAPPINGENABLED 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. VMVCACHEMAX Maximum desired size of the cache queue. VMVCACHEMIN Minimum desired size of the cache queue. If the cache queue size falls very far below this value, the pageout daemon is awakened. VMVFREEMIN Minimum amount of memory (cache memory plus free memory) requiredto be available before a process waiting on memory will be awak-
ened. VMVFREERESERVED Processes will awaken the pageout daemon and wait for memory if the number of free and cached pages drops below this value. VMVFREETARGET The total amount of free memory (including cache memory) that the pageout daemon tries to maintain. VMVINACTIVETARGET 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. VMVPAGEOUTFREEMIN If the amount of free and cache memory falls below this value, the pageout daemon will enter "memory conserving mode" to avoid deadlock.RETURN VALUES
Upon successful completion, the value 0 is returned; otherwise thevalue -1 is returned and the global variable errno is set to indicate the
error. EERRRROORRSS The following errors may be reported: [EFAULT] The buffer name, oldp, newp, or length pointer oldlenp contains an invalid address. [EINVAL] The name array is less than two or greater thanCTLMAXNAME.
[EINVAL] A non-null newp is given and its specified length in
newlen is too large or too small. [ENOMEM] The length pointed to by oldlenp is too short to hold the requested value. [ENOMEM] The smaller of either the length pointed to by oldlenp or the estimated size of the returned data exceeds the system limit on locked memory. [ENOMEM] Locking the buffer oldp, or a portion of the buffer if the estimated size of the data to be returned issmaller, would cause the process to exceed its per-
process locked memory limit. [ENOTDIR] The name array specifies an intermediate rather than terminal name. [EISDIR] The name array specifies a terminal name, but the actual name is not terminal. [ENOENT] The name array specifies a value that is unknown.[EPERM] An attempt is made to set a read-only value.
[EPERM] A process without appropriate privilege attempts to set a value. FILESdefinitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers definitions for second level network identifiers definitions for third level profiling identifiers fiers
definitions for second level virtual memory identi- definitions for third level IPv4/IPv6 identifiers and fourth level IPv4/v6 identifiers definitions for fourth level ICMP identifiers definitions for fourth level ICMPv6 identifiers definitions for fourth level UDP identifiers SEE ALSO
sysconf(3), sysctl(8) HISTORY The ssyyssccttll() function first appeared in 4.4BSD. BSD January 23, 2001 BSD