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 6.6 (Berkeley) 05/14/93 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\_CHOWN\_RESTRICTED integer no 204.It KERN\_CLOCKRATE struct clockinfo no 205.It KERN\_FILE struct file no 206.It KERN\_HOSTID integer yes 207.It KERN\_HOSTNAME string yes 208.It KERN\_JOB\_CONTROL integer no 209.It KERN\_LINK\_MAX integer no 210.It KERN\_MAXFILES integer yes 211.It KERN\_MAXPROC integer yes 212.It KERN\_MAXVNODES integer yes 213.It KERN\_MAX\_CANON integer no 214.It KERN\_MAX\_INPUT integer no 215.It KERN\_NAME\_MAX integer no 216.It KERN\_NGROUPS integer no 217.It KERN\_NO\_TRUNC integer no 218.It KERN\_OSRELEASE string no 219.It KERN\_OSREV integer no 220.It KERN\_OSTYPE string no 221.It KERN\_PATH\_MAX integer no 222.It KERN\_PIPE\_BUF integer no 223.It KERN\_POSIX1 integer no 224.It KERN\_PROC struct proc no 225.It KERN\_PROF node not applicable 226.It KERN\_SAVED\_IDS integer no 227.It KERN\_SECURELVL integer raise only 228.It KERN\_VDISABLE integer no 229.It KERN\_VERSION string no 230.It KERN\_VNODE struct vnode no 231.El 232.Pp 233.Bl -tag -width "123456" 234.It Li KERN_ARGMAX 235Maximum bytes of argument to exec. 236.It Li KERN_CHOWN_RESTRICTED 237Return 1 if appropriate privileges are required for the 238.Xr chown 2 239system call, otherwise 0. 240.It Li KERN_CLOCKRATE 241A 242.Va struct clockinfo 243structure is returned. 244This structure contains the clock, statistics clock and profiling clock 245frequencies, and the number of micro-seconds per hz tick. 246.It Li KERN_FILE 247Return the entire file table. 248The returned data consists of a single 249.Va struct filehead 250followed by an array of 251.Va struct file , 252whose size depends on the current number of such objects in the system. 253.It Li KERN_HOSTID 254Get or set the host id. 255.It Li KERN_HOSTNAME 256Get or set the hostname. 257.It Li KERN_JOB_CONTROL 258Return 1 if job control is available on this system, otherwise 0. 259.It Li KERN_LINK_MAX 260The maximum file link count. 261.It Li KERN_MAXFILES 262The maximum number of open files that may be open in the system. 263.It Li KERN_MAXPROC 264The maximum number of simultaneous processes the system will allow. 265.It Li KERN_MAXVNODES 266The maximum number of vnodes available on the system. 267.It Li KERN_MAX_CANON 268The maximum number of bytes in terminal canonical input line. 269.It Li KERN_MAX_INPUT 270The minimum number of bytes for which space is available in 271a terminal input queue. 272.It Li KERN_NAME_MAX 273The maximum number of bytes in a file name. 274.It Li KERN_NGROUPS 275The maximum number of supplemental groups. 276.It Li KERN_NO_TRUNC 277Return 1 if file names longer than KERN_NAME_MAX are truncated. 278.It Li KERN_OSRELEASE 279The system release string. 280.It Li KERN_OSREV 281The system revision string. 282.It Li KERN_OSTYPE 283The system type string. 284.It Li KERN_PATH_MAX 285The maximum number of bytes in a pathname. 286.It Li KERN_PIPE_BUF 287The maximum number of bytes which will be written atomically to a pipe. 288.It Li KERN_POSIX1 289The POSIX 1003.1 version with which the system attempts to comply. 290.It Li KERN_PROC 291Return the entire process table, or a subset of it. 292An array of 293.Va struct kinfo_proc 294structures is returned, 295whose size depends on the current number of such objects in the system. 296The third and fourth level names are as follows: 297.Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent 298.It Pa Third level name Fourth level is: 299.It KERN\_PROC\_ALL None 300.It KERN\_PROC\_PID A process ID 301.It KERN\_PROC\_PGRP A process group 302.It KERN\_PROC\_TTY A tty device 303.It KERN\_PROC\_UID A user ID 304.It KERN\_PROC\_RUID A real user ID 305.El 306.It Li KERN_PROF 307Return profiling information about the kernel. 308If the kernel is not compiled for profiling, 309attempts to retrieve any of the KERN_PROF values will 310fail with EOPNOTSUPP. 311The third level names for the string and integer profiling information 312is detailed below. 313The changeable column shows whether a process with appropriate 314privilege may change the value. 315.Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent 316.It Sy Pa Third level name Type Changeable 317.It GPROF\_STATE integer yes 318.It GPROF\_COUNT u_short[\|] yes 319.It GPROF\_FROMS u_short[\|] yes 320.It GPROF\_TOS struct tostruct yes 321.It GPROF\_GMONPARAM struct gmonparam no 322.El 323.Pp 324The variables are as follows: 325.Bl -tag -width "123456" 326.It Li GPROF_STATE 327Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling 328is running or stopped. 329.It Li GPROF_COUNT 330Array of statistical program counter counts. 331.It Li GPROF_FROMS 332Array indexed by program counter of call-from points. 333.It Li GPROF_TOS 334Array of 335.Va struct tostruct 336describing destination of calls and their counts. 337.It Li GPROF_GMONPARAM 338Structure giving the sizes of the above arrays. 339.El 340.It Li KERN_SAVED_IDS 341Returns 1 if saved set-group and saved set-user ID is available. 342.It Li KERN_SECURELVL 343The system security level. 344This level may be raised by processes with appropriate privilege. 345It may only be lowered by process 1. 346.It Li KERN_VDISABLE 347Returns the terminal character disabling value. 348.It Li KERN_VERSION 349The system version string. 350.It Li KERN_VNODE 351Return the entire vnode table. 352Note, the vnode table is not necessarily a consistent snapshot of 353the system. 354The returned data consists of an array whose size depends on the 355current number of such objects in the system. 356Each element of the array contains the kernel address of a vnode 357.Va struct vnode * 358followed by the vnode itself 359.Va struct vnode . 360.El 361.Sh CTL_MACHDEP 362There are currently no second level names for the machine dependent 363interface. 364.Sh CTL_NET 365The string and integer information available for the CTL_NET level 366is detailed below. 367The changeable column shows whether a process with appropriate 368privilege may change the value. 369.Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent 370.It Sy Pa Second level name Type Changeable 371.It PF\_ROUTE routing messages no 372.It PF\_INET internet values yes 373.El 374.Pp 375.Bl -tag -width "123456" 376.It Li PF_ROUTE 377Return the entire routing table or a subset of it. 378The data is returned as a sequence of routing messages (see 379.Xr route 4 380for the header file, format and meaning). 381The length of each message is contained in the message header. 382.Pp 383The third level name is a protocol number, which is currently always 0. 384The fourth level name is an address family, which may be set to 0 to 385select all address families. 386The fifth and sixth level names are as follows: 387.Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent 388.It Pa Fifth level name Sixth level is: 389.It NET\_RT\_FLAGS rtflags 390.It NET\_RT\_DUMP None 391.It NET\_RT\_IFLIST None 392.El 393.It Li PF_INET 394Get or set various global information about the internet protocols. 395The third level name is the protocol. 396The fourth level name is the variable name. 397The currently defined protocols and names are: 398.Bl -column "Protocol nameXXXXXX" "Variable nameXXX" "integerXXX" -offset indent 399.It Pa Protocol name Variable name Type Changeable 400.It ip forwarding integer yes 401.It ip redirect integer yes 402.It ip ttl integer yes 403.It icmp maskrepl integer yes 404.It udp checksum integer yes 405.El 406.Pp 407The variables are as follows: 408.Bl -tag -width "123456" 409.It Li ip.forwarding 410Returns 1 when IP forwarding is enabled for the host, 411meaning that the host is acting as a router. 412.It Li ip.redirect 413Returns 1 when ICMP redirects may be sent by the host. 414This option is ignored unless the host is routing IP packets, 415and should normally be enabled on all systems. 416.It Li ip.ttl 417The maximum time-to-live (hop count) value for an IP packet sourced by 418the system. 419This value applies to normal transport protocols, not to ICMP. 420.It Li icmp.maskrepl 421Returns 1 if ICMP network mask requests are to be answered. 422.It Li udp.checksum 423Returns 1 when UDP checksums are being computed and checked. 424Disabling UDP checksums is strongly discouraged. 425.El 426.Sh CTL_USER 427The string and integer information available for the CTL_USER level 428is detailed below. 429The changeable column shows whether a process with appropriate 430privilege may change the value. 431.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent 432.It Sy Pa Second level name Type Changeable 433.It USER\_BC\_BASE\_MAX integer no 434.It USER\_BC\_DIM\_MAX integer no 435.It USER\_BC\_SCALE\_MAX integer no 436.It USER\_BC\_STRING\_MAX integer no 437.It USER\_COLL\_WEIGHTS\_MAX integer no 438.It USER\_CS\_PATH string no 439.It USER\_EXPR\_NEST\_MAX integer no 440.It USER\_LINE\_MAX integer no 441.It USER\_POSIX2\_CHAR\_TERM integer no 442.It USER\_POSIX2\_C\_BIND integer no 443.It USER\_POSIX2\_C\_DEV integer no 444.It USER\_POSIX2\_FORT\_DEV integer no 445.It USER\_POSIX2\_FORT\_RUN integer no 446.It USER\_POSIX2\_LOCALEDEF integer no 447.It USER\_POSIX2\_SW\_DEV integer no 448.It USER\_POSIX2\_UPE integer no 449.It USER\_POSIX2\_VERSION integer no 450.It USER\_RE\_DUP\_MAX integer no 451.El 452.Bl -tag -width "123456" 453.Pp 454.It Li USER_BC_BASE_MAX 455The maximum ibase/obase values in the 456.Xr bc 1 457utility 458.It Li USER_BC_DIM_MAX 459The maximum array size in the 460.Xr bc 1 461utility. 462.It Li USER_BC_SCALE_MAX 463The maximum scale value in the 464.Xr bc 1 465utility. 466.It Li USER_BC_STRING_MAX 467The maximum string length in the 468.Xr bc 1 469utility. 470.It Li USER_COLL_WEIGHTS_MAX 471The maximum number of weights that can be assigned to any entry of 472the LC_COLLATE order keyword in the locale definition file. 473.It Li USER_CS_PATH 474Return a value for the 475.Ev PATH 476environment variable that finds all the standard utilities. 477.It Li USER_EXPR_NEST_MAX 478The maximum number of expressions that can be nested within 479parenthesis by the 480.Xr expr 1 481utility. 482.It Li USER_LINE_MAX 483The maximum length in bytes of a text-processing utility's input 484line. 485.It Li USER_POSIX2_CHAR_TERM 486Return 1 if the system supports at least one terminal type capable of 487all operations described in POSIX 1003.2, otherwise 0. 488.It Li USER_POSIX2_C_BIND 489Return 1 if the system's C-language development facilities support the 490C-Language Bindings Option, otherwise 0. 491.It Li USER_POSIX2_C_DEV 492Return 1 if the system supports the C-Language Development Utilities Option, 493otherwise 0. 494.It Li USER_POSIX2_FORT_DEV 495Return 1 if the system supports the FORTRAN Development Utilities Option, 496otherwise 0. 497.It Li USER_POSIX2_FORT_RUN 498Return 1 if the system supports the FORTRAN Runtime Utilities Option, 499otherwise 0. 500.It Li USER_POSIX2_LOCALEDEF 501Return 1 if the system supports the creation of locales, otherwise 0. 502.It Li USER_POSIX2_SW_DEV 503Return 1 if the system supports the Software Development Utilities Option, 504otherwise 0. 505.It Li USER_POSIX2_UPE 506Return 1 if the system supports the User Portability Utilities Option, 507otherwise 0. 508.It Li USER_POSIX2_VERSION 509The POSIX 1003.2 version with which the system attempts to comply. 510.It Li USER_RE_DUP_MAX 511The maximum number of repeated occurrences of a regular expression 512permitted when using interval notation. 513.El 514.Sh CTL_VM 515The string and integer information available for the CTL_VM level 516is detailed below. 517The changeable column shows whether a process with appropriate 518privilege may change the value. 519.Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent 520.It Sy Pa Second level name Type Changeable 521.It VM\_LOADAVG struct loadavg no 522.It VM\_METER struct vmtotal no 523.El 524.Pp 525.Bl -tag -width "123456" 526.It Li VM_LOADAVG 527Return the load average history. 528The returned data consists of a 529.Va struct loadavg . 530.It Li VM_METER 531Return the system wide virtual memory statistics. 532The returned data consists of a 533.Va struct vmtotal . 534.El 535.Sh RETURN VALUES 536If the call to 537.Nm sysctl 538is successful, 0 is returned. 539Otherwise \-1 is returned and 540.Va errno 541is set appropriately. 542.Sh ERRORS 543The following errors may be reported: 544.Bl -tag -width Er 545.It Bq Er EFAULT 546The buffer 547.Fa name , 548.Fa oldp , 549.Fa newp , 550or length pointer 551.Fa oldlenp 552contains an invalid address. 553.It Bq Er EINVAL 554The 555.Fa name 556array is less than two or greater than CTL_MAXNAME. 557.It Bq Er EINVAL 558A non-null 559.Fa newp 560is given and its specified length in 561.Fa newlen 562is too large or too small. 563.It Bq Er ENOMEM 564The length pointed to by 565.Fa oldlenp 566is too short to hold the requested value. 567.It Bq Er ENOTDIR 568The 569.Fa name 570array specifies an intermediate rather than terminal name. 571.It Bq Er EOPNOTSUPP 572The 573.Fa name 574array specifies a value that is unknown. 575.It Bq Er EPERM 576An attempt is made to set a read-only value. 577.It Bq Er EPERM 578A process without appropriate privilege attempts to set a value. 579.El 580.Sh FILES 581.Bl -tag -width <netinet/icmpXvar.h> -compact 582.It Pa <sys/sysctl.h> 583definitions for top level identifiers, second level kernel and hardware 584identifiers, and user level identifiers 585.It Pa <sys/socket.h> 586definitions for second level network identifiers 587.It Pa <sys/gmon.h> 588definitions for third level profiling identifiers 589.It Pa <vm/vm_param.h> 590definitions for second level virtual memory identifiers 591.It Pa <netinet/in.h> 592definitions for third level Internet identifiers and 593fourth level IP identifiers 594.It Pa <netinet/icmp_var.h> 595definitions for fourth level ICMP identifiers 596.It Pa <netinet/udp_var.h> 597definitions for fourth level UDP identifiers 598.El 599.Sh SEE ALSO 600.Xr sysctl 8 601.Sh HISTORY 602The 603.Nm sysctl 604function first appeared in 4.4BSD. 605