1.\" Copyright (c) 1993 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" %sccs.include.redist.roff% 5.\" 6.\" @(#)sysctl.3 6.10 (Berkeley) 05/24/93 7.\" 8.Dd "" 9.Dt SYSCTL 3 10.Os 11.Sh NAME 12.Nm sysctl 13.Nd get or set system information 14.Sh SYNOPSIS 15.Fd #include <sys/sysctl.h> 16.Ft int 17.Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen" 18.Sh DESCRIPTION 19The 20.Nm sysctl 21function retrieves system information and allows processes with 22appropriate privileges to set system information. 23The information available from 24.Nm sysctl 25consists of integers, strings, and tables. 26Information may be retrieved and set from the command interface 27using the 28.Xr sysctl 1 29utility. 30.Pp 31Unless explicitly noted below, 32.Nm sysctl 33returns a consistent snapshot of the data requested. 34Consistency is obtained by locking the destination 35buffer into memory so that the data may be copied out without blocking. 36Calls to 37.Nm sysctl 38are serialized to avoid deadlock. 39.Pp 40The state is described using a ``Management Information Base'' (MIB) 41style name, listed in 42.Fa name , 43which is a 44.Fa namelen 45length array of integers. 46.Pp 47The information is copied into the buffer specified by 48.Fa oldp . 49The size of the buffer is given by the location specified by 50.Fa oldlenp 51before the call, 52and that location gives the amount of data copied after a successful call. 53If the amount of data available is greater 54than the size of the buffer supplied, 55the call supplies as much data as fits in the buffer provided 56and returns with the error code ENOMEM. 57If the old value is not desired, 58.Fa oldp 59and 60.Fa oldlenp 61should be set to NULL. 62.Pp 63The size of the available data can be determined by calling 64.Nm sysctl 65with a NULL parameter for 66.Fa oldp . 67The size of the available data will be returned in the location pointed to by 68.Fa oldlenp . 69For some operations, the amount of space may change often. 70For these operations, 71the system attempts to round up so that the returned size is 72large enough for a call to return the data shortly thereafter. 73.Pp 74To set a new value, 75.Fa newp 76is set to point to a buffer of length 77.Fa newlen 78from which the requested value is to be taken. 79If a new value is not to be set, 80.Fa newp 81should be set to NULL and 82.Fa newlen 83set to 0. 84.Pp 85The top level names are defined with a CTL_ prefix in 86.Pa <sys/sysctl.h> , 87and are as follows. 88The next and subsequent levels down are found in the include files 89listed here, and described in separate sections below. 90.Pp 91.Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent 92.It Sy Pa Name Next level names Description 93.It CTL\_DEBUG sys/sysctl.h Debugging 94.It CTL\_FS sys/sysctl.h File system 95.It CTL\_HW sys/sysctl.h Generic CPU, I/O 96.It CTL\_KERN sys/sysctl.h High kernel: processes, limits 97.It CTL\_MACHDEP sys/sysctl.h Machine dependent 98.It CTL\_NET sys/socket.h Networking 99.It CTL\_USER sys/sysctl.h User-level 100.It CTL\_VM vm/vm_param.h Virtual memory 101.El 102.Pp 103For example, the following retrieves the maximum number of processes allowed 104in the system: 105.Bd -literal -offset indent -compact 106int mib[2], maxproc; 107size_t len; 108.sp 109mib[0] = CTL_KERN; 110mib[1] = KERN_MAXPROC; 111len = sizeof(maxproc); 112sysctl(mib, 2, &maxproc, &len, NULL, 0); 113.Ed 114.sp 115To retrieve the standard search path for the system utilities: 116.Bd -literal -offset indent -compact 117int mib[2]; 118size_t len; 119char *p; 120.sp 121mib[0] = CTL_USER; 122mib[1] = USER_CS_PATH; 123sysctl(mib, 2, NULL, &len, NULL, 0); 124p = malloc(len); 125sysctl(mib, 2, p, &len, NULL, 0); 126.Ed 127.Sh CTL_DEBUG 128The debugging variables vary from system to system. 129A debugging variable may be added or deleted without need to recompile 130.Nm sysctl 131to know about it. 132Each time it runs, 133.Nm sysctl 134gets the list of debugging variables from the kernel and 135displays their current values. 136The system defines twenty 137.Ns ( Va struct ctldebug ) 138variables named 139.Nm debug0 140through 141.Nm debug19 . 142They are declared as separate variables so that they can be 143individually initialized at the location of their associated variable. 144The loader prevents multiple use of the same variable by issuing errors 145if a variable is initialized in more than one place. 146For example, to export the variable 147.Nm dospecialcheck 148as a debugging variable, the following declaration would be used: 149.Bd -literal -offset indent -compact 150int dospecialcheck = 1; 151struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck }; 152.Ed 153.Sh CTL_FS 154There are currently no second level names for the file system. 155.Sh CTL_HW 156The string and integer information available for the CTL_HW level 157is detailed below. 158The changeable column shows whether a process with appropriate 159privilege may change the value. 160.Bl -column "Second level nameXXXXXX" integerXXX -offset indent 161.It Sy Pa Second level name Type Changeable 162.It HW\_MACHINE string no 163.It HW\_MODEL string no 164.It HW\_NCPU integer no 165.It HW\_BYTEORDER integer no 166.It HW\_PHYSMEM integer no 167.It HW\_USERMEM integer no 168.It HW\_PAGESIZE integer no 169.\".It HW\_DISKNAMES integer no 170.\".It HW\_DISKSTATS integer no 171.El 172.Pp 173.Bl -tag -width "123456" 174.It Li HW_MACHINE 175The machine class. 176.It Li HW_MODEL 177The machine model 178.It Li HW_NCPU 179The number of cpus. 180.It Li HW_BYTEORDER 181The byteorder (4,321, or 1,234). 182.It Li HW_PHYSMEM 183The bytes of physical memory. 184.It Li HW_USERMEM 185The bytes of non-kernel memory. 186.It Li HW_PAGESIZE 187The software page size. 188.\".It Fa HW_DISKNAMES 189.\".It Fa HW_DISKSTATS 190.El 191.Sh CTL_KERN 192The string and integer information available for the CTL_KERN level 193is detailed below. 194The changeable column shows whether a process with appropriate 195privilege may change the value. 196The types of data currently available are process information, 197system vnodes, the open file entries, routing table entries, 198virtual memory statistics, load average history, and clock rate 199information. 200.Bl -column "KERNXCHOWNXRESTRICTEDXXX" "struct clockrateXXX" -offset indent 201.It Sy Pa Second level name Type Changeable 202.It KERN\_ARGMAX integer no 203.It KERN\_BOOTTIME struct timeval no 204.It KERN\_CHOWN\_RESTRICTED integer no 205.It KERN\_CLOCKRATE struct clockinfo no 206.It KERN\_FILE struct file no 207.It KERN\_HOSTID integer yes 208.It KERN\_HOSTNAME string yes 209.It KERN\_JOB\_CONTROL integer no 210.It KERN\_LINK\_MAX integer no 211.It KERN\_MAXFILES integer yes 212.It KERN\_MAXPROC integer yes 213.It KERN\_MAXVNODES integer yes 214.It KERN\_MAX\_CANON integer no 215.It KERN\_MAX\_INPUT integer no 216.It KERN\_NAME\_MAX integer no 217.It KERN\_NGROUPS integer no 218.It KERN\_NO\_TRUNC integer no 219.It KERN\_OSRELEASE string no 220.It KERN\_OSREV integer no 221.It KERN\_OSTYPE string no 222.It KERN\_PATH\_MAX integer no 223.It KERN\_PIPE\_BUF integer no 224.It KERN\_POSIX1 integer no 225.It KERN\_PROC struct proc no 226.It KERN\_PROF node not applicable 227.It KERN\_SAVED\_IDS integer no 228.It KERN\_SECURELVL integer raise only 229.It KERN\_VDISABLE integer no 230.It KERN\_VERSION string no 231.It KERN\_VNODE struct vnode no 232.El 233.Pp 234.Bl -tag -width "123456" 235.It Li KERN_ARGMAX 236The maximum bytes of argument to 237.Xr exec 2 . 238.It Li KERN_BOOTTIME 239A 240.Va struct timeval 241structure is returned. 242This structure contains the time that the system was booted. 243.It Li KERN_CHOWN_RESTRICTED 244Return 1 if appropriate privileges are required for the 245.Xr chown 2 246system call, otherwise 0. 247.It Li KERN_CLOCKRATE 248A 249.Va struct clockinfo 250structure is returned. 251This structure contains the clock, statistics clock and profiling clock 252frequencies, and the number of micro-seconds per hz tick. 253.It Li KERN_FILE 254Return the entire file table. 255The returned data consists of a single 256.Va struct filehead 257followed by an array of 258.Va struct file , 259whose size depends on the current number of such objects in the system. 260.It Li KERN_HOSTID 261Get or set the host id. 262.It Li KERN_HOSTNAME 263Get or set the hostname. 264.It Li KERN_JOB_CONTROL 265Return 1 if job control is available on this system, otherwise 0. 266.It Li KERN_LINK_MAX 267The maximum file link count. 268.It Li KERN_MAXFILES 269The maximum number of open files that may be open in the system. 270.It Li KERN_MAXPROC 271The maximum number of simultaneous processes the system will allow. 272.It Li KERN_MAXVNODES 273The maximum number of vnodes available on the system. 274.It Li KERN_MAX_CANON 275The maximum number of bytes in terminal canonical input line. 276.It Li KERN_MAX_INPUT 277The minimum maximum number of bytes for which space is available in 278a terminal input queue. 279.It Li KERN_NAME_MAX 280The maximum number of bytes in a file name. 281.It Li KERN_NGROUPS 282The maximum number of supplemental groups. 283.It Li KERN_NO_TRUNC 284Return 1 if file names longer than KERN_NAME_MAX are truncated. 285.It Li KERN_OSRELEASE 286The system release string. 287.It Li KERN_OSREV 288The system revision string. 289.It Li KERN_OSTYPE 290The system type string. 291.It Li KERN_PATH_MAX 292The maximum number of bytes in a pathname. 293.It Li KERN_PIPE_BUF 294The maximum number of bytes which will be written atomically to a pipe. 295.It Li KERN_POSIX1 296The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 297attempts to comply. 298.It Li KERN_PROC 299Return the entire process table, or a subset of it. 300An array of 301.Va struct kinfo_proc 302structures is returned, 303whose size depends on the current number of such objects in the system. 304The third and fourth level names are as follows: 305.Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent 306.It Pa Third level name Fourth level is: 307.It KERN\_PROC\_ALL None 308.It KERN\_PROC\_PID A process ID 309.It KERN\_PROC\_PGRP A process group 310.It KERN\_PROC\_TTY A tty device 311.It KERN\_PROC\_UID A user ID 312.It KERN\_PROC\_RUID A real user ID 313.El 314.It Li KERN_PROF 315Return profiling information about the kernel. 316If the kernel is not compiled for profiling, 317attempts to retrieve any of the KERN_PROF values will 318fail with EOPNOTSUPP. 319The third level names for the string and integer profiling information 320is detailed below. 321The changeable column shows whether a process with appropriate 322privilege may change the value. 323.Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent 324.It Sy Pa Third level name Type Changeable 325.It GPROF\_STATE integer yes 326.It GPROF\_COUNT u_short[\|] yes 327.It GPROF\_FROMS u_short[\|] yes 328.It GPROF\_TOS struct tostruct yes 329.It GPROF\_GMONPARAM struct gmonparam no 330.El 331.Pp 332The variables are as follows: 333.Bl -tag -width "123456" 334.It Li GPROF_STATE 335Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling 336is running or stopped. 337.It Li GPROF_COUNT 338Array of statistical program counter counts. 339.It Li GPROF_FROMS 340Array indexed by program counter of call-from points. 341.It Li GPROF_TOS 342Array of 343.Va struct tostruct 344describing destination of calls and their counts. 345.It Li GPROF_GMONPARAM 346Structure giving the sizes of the above arrays. 347.El 348.It Li KERN_SAVED_IDS 349Returns 1 if saved set-group and saved set-user ID is available. 350.It Li KERN_SECURELVL 351The system security level. 352This level may be raised by processes with appropriate privilege. 353It may only be lowered by process 1. 354.It Li KERN_VDISABLE 355Returns the terminal character disabling value. 356.It Li KERN_VERSION 357The system version string. 358.It Li KERN_VNODE 359Return the entire vnode table. 360Note, the vnode table is not necessarily a consistent snapshot of 361the system. 362The returned data consists of an array whose size depends on the 363current number of such objects in the system. 364Each element of the array contains the kernel address of a vnode 365.Va struct vnode * 366followed by the vnode itself 367.Va struct vnode . 368.El 369.Sh CTL_MACHDEP 370There are currently no second level names for the machine dependent 371interface. 372.Sh CTL_NET 373The string and integer information available for the CTL_NET level 374is detailed below. 375The changeable column shows whether a process with appropriate 376privilege may change the value. 377.Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent 378.It Sy Pa Second level name Type Changeable 379.It PF\_ROUTE routing messages no 380.It PF\_INET internet values yes 381.El 382.Pp 383.Bl -tag -width "123456" 384.It Li PF_ROUTE 385Return the entire routing table or a subset of it. 386The data is returned as a sequence of routing messages (see 387.Xr route 4 388for the header file, format and meaning). 389The length of each message is contained in the message header. 390.Pp 391The third level name is a protocol number, which is currently always 0. 392The fourth level name is an address family, which may be set to 0 to 393select all address families. 394The fifth and sixth level names are as follows: 395.Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent 396.It Pa Fifth level name Sixth level is: 397.It NET\_RT\_FLAGS rtflags 398.It NET\_RT\_DUMP None 399.It NET\_RT\_IFLIST None 400.El 401.It Li PF_INET 402Get or set various global information about the internet protocols. 403The third level name is the protocol. 404The fourth level name is the variable name. 405The currently defined protocols and names are: 406.Bl -column "Protocol nameXXXXXX" "Variable nameXXX" "integerXXX" -offset indent 407.It Pa Protocol name Variable name Type Changeable 408.It ip forwarding integer yes 409.It ip redirect integer yes 410.It ip ttl integer yes 411.It icmp maskrepl integer yes 412.It udp checksum integer yes 413.El 414.Pp 415The variables are as follows: 416.Bl -tag -width "123456" 417.It Li ip.forwarding 418Returns 1 when IP forwarding is enabled for the host, 419meaning that the host is acting as a router. 420.It Li ip.redirect 421Returns 1 when ICMP redirects may be sent by the host. 422This option is ignored unless the host is routing IP packets, 423and should normally be enabled on all systems. 424.It Li ip.ttl 425The maximum time-to-live (hop count) value for an IP packet sourced by 426the system. 427This value applies to normal transport protocols, not to ICMP. 428.It Li icmp.maskrepl 429Returns 1 if ICMP network mask requests are to be answered. 430.It Li udp.checksum 431Returns 1 when UDP checksums are being computed and checked. 432Disabling UDP checksums is strongly discouraged. 433.El 434.Sh CTL_USER 435The string and integer information available for the CTL_USER level 436is detailed below. 437The changeable column shows whether a process with appropriate 438privilege may change the value. 439.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent 440.It Sy Pa Second level name Type Changeable 441.It USER\_BC\_BASE\_MAX integer no 442.It USER\_BC\_DIM\_MAX integer no 443.It USER\_BC\_SCALE\_MAX integer no 444.It USER\_BC\_STRING\_MAX integer no 445.It USER\_COLL\_WEIGHTS\_MAX integer no 446.It USER\_CS\_PATH string no 447.It USER\_EXPR\_NEST\_MAX integer no 448.It USER\_LINE\_MAX integer no 449.It USER\_POSIX2\_CHAR\_TERM integer no 450.It USER\_POSIX2\_C\_BIND integer no 451.It USER\_POSIX2\_C\_DEV integer no 452.It USER\_POSIX2\_FORT\_DEV integer no 453.It USER\_POSIX2\_FORT\_RUN integer no 454.It USER\_POSIX2\_LOCALEDEF integer no 455.It USER\_POSIX2\_SW\_DEV integer no 456.It USER\_POSIX2\_UPE integer no 457.It USER\_POSIX2\_VERSION integer no 458.It USER\_RE\_DUP\_MAX integer no 459.It USER\_STREAM\_MAX integer no 460.It USER\_TZNAME\_MAX integer no 461.El 462.Bl -tag -width "123456" 463.Pp 464.It Li USER_BC_BASE_MAX 465The maximum ibase/obase values in the 466.Xr bc 1 467utility. 468.It Li USER_BC_DIM_MAX 469The maximum array size in the 470.Xr bc 1 471utility. 472.It Li USER_BC_SCALE_MAX 473The maximum scale value in the 474.Xr bc 1 475utility. 476.It Li USER_BC_STRING_MAX 477The maximum string length in the 478.Xr bc 1 479utility. 480.It Li USER_COLL_WEIGHTS_MAX 481The maximum number of weights that can be assigned to any entry of 482the LC_COLLATE order keyword in the locale definition file. 483.It Li USER_CS_PATH 484Return a value for the 485.Ev PATH 486environment variable that finds all the standard utilities. 487.It Li USER_EXPR_NEST_MAX 488The maximum number of expressions that can be nested within 489parenthesis by the 490.Xr expr 1 491utility. 492.It Li USER_LINE_MAX 493The maximum length in bytes of a text-processing utility's input 494line. 495.It Li USER_POSIX2_CHAR_TERM 496Return 1 if the system supports at least one terminal type capable of 497all operations described in POSIX 1003.2, otherwise 0. 498.It Li USER_POSIX2_C_BIND 499Return 1 if the system's C-language development facilities support the 500C-Language Bindings Option, otherwise 0. 501.It Li USER_POSIX2_C_DEV 502Return 1 if the system supports the C-Language Development Utilities Option, 503otherwise 0. 504.It Li USER_POSIX2_FORT_DEV 505Return 1 if the system supports the FORTRAN Development Utilities Option, 506otherwise 0. 507.It Li USER_POSIX2_FORT_RUN 508Return 1 if the system supports the FORTRAN Runtime Utilities Option, 509otherwise 0. 510.It Li USER_POSIX2_LOCALEDEF 511Return 1 if the system supports the creation of locales, otherwise 0. 512.It Li USER_POSIX2_SW_DEV 513Return 1 if the system supports the Software Development Utilities Option, 514otherwise 0. 515.It Li USER_POSIX2_UPE 516Return 1 if the system supports the User Portability Utilities Option, 517otherwise 0. 518.It Li USER_POSIX2_VERSION 519The version of POSIX 1003.2 with which the system attempts to comply. 520.It Li USER_RE_DUP_MAX 521The maximum number of repeated occurrences of a regular expression 522permitted when using interval notation. 523.It Li USER_STREAM_MAX 524The minimum maximum number of streams that a process may have open 525at any one time. 526.It Li USER_TZNAME_MAX 527The minimum maximum number of types supported for the name of a 528timezone. 529.El 530.Sh CTL_VM 531The string and integer information available for the CTL_VM level 532is detailed below. 533The changeable column shows whether a process with appropriate 534privilege may change the value. 535.Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent 536.It Sy Pa Second level name Type Changeable 537.It VM\_LOADAVG struct loadavg no 538.It VM\_METER struct vmtotal no 539.El 540.Pp 541.Bl -tag -width "123456" 542.It Li VM_LOADAVG 543Return the load average history. 544The returned data consists of a 545.Va struct loadavg . 546.It Li VM_METER 547Return the system wide virtual memory statistics. 548The returned data consists of a 549.Va struct vmtotal . 550.El 551.Sh RETURN VALUES 552If the call to 553.Nm sysctl 554is successful, 0 is returned. 555Otherwise \-1 is returned and 556.Va errno 557is set appropriately. 558.Sh ERRORS 559The following errors may be reported: 560.Bl -tag -width Er 561.It Bq Er EFAULT 562The buffer 563.Fa name , 564.Fa oldp , 565.Fa newp , 566or length pointer 567.Fa oldlenp 568contains an invalid address. 569.It Bq Er EINVAL 570The 571.Fa name 572array is less than two or greater than CTL_MAXNAME. 573.It Bq Er EINVAL 574A non-null 575.Fa newp 576is given and its specified length in 577.Fa newlen 578is too large or too small. 579.It Bq Er ENOMEM 580The length pointed to by 581.Fa oldlenp 582is too short to hold the requested value. 583.It Bq Er ENOTDIR 584The 585.Fa name 586array specifies an intermediate rather than terminal name. 587.It Bq Er EOPNOTSUPP 588The 589.Fa name 590array specifies a value that is unknown. 591.It Bq Er EPERM 592An attempt is made to set a read-only value. 593.It Bq Er EPERM 594A process without appropriate privilege attempts to set a value. 595.El 596.Sh FILES 597.Bl -tag -width <netinet/icmpXvar.h> -compact 598.It Pa <sys/sysctl.h> 599definitions for top level identifiers, second level kernel and hardware 600identifiers, and user level identifiers 601.It Pa <sys/socket.h> 602definitions for second level network identifiers 603.It Pa <sys/gmon.h> 604definitions for third level profiling identifiers 605.It Pa <vm/vm_param.h> 606definitions for second level virtual memory identifiers 607.It Pa <netinet/in.h> 608definitions for third level Internet identifiers and 609fourth level IP identifiers 610.It Pa <netinet/icmp_var.h> 611definitions for fourth level ICMP identifiers 612.It Pa <netinet/udp_var.h> 613definitions for fourth level UDP identifiers 614.El 615.Sh SEE ALSO 616.Xr sysctl 8 617.Sh HISTORY 618The 619.Nm sysctl 620function first appeared in 4.4BSD. 621