1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.roff% 5.\" 6.\" @(#)sysctl.3 8.4 (Berkeley) 05/09/95 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\_VFS sys/mount.h Filesystem 95.It CTL\_HW sys/sysctl.h Generic CPU, I/O 96.It CTL\_KERN sys/sysctl.h High kernel 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_VFS 154A distinguished second level name, VFS_GENERIC, 155is used to get general information about all filesystems. 156One of its third level identifiers is VFS_MAXTYPENUM 157that gives the highest valid filesystem type number. 158Its other third level identifier is VFS_CONF that 159returns configuration information about the filesystem 160type given as a fourth level identifier (see 161.Xr getvfsbyname 3 162as an example of its use). 163The remaining second level identifiers are the 164filesystem type number returned by a 165.Xr statfs 2 166call or from VFS_CONF. 167The third level identifiers available for each filesystem 168are given in the header file that defines the mount 169argument structure for that filesystem. 170.Sh CTL_HW 171The string and integer information available for the CTL_HW level 172is detailed below. 173The changeable column shows whether a process with appropriate 174privilege may change the value. 175.Bl -column "Second level nameXXXXXX" integerXXX -offset indent 176.It Sy Pa Second level name Type Changeable 177.It HW\_MACHINE string no 178.It HW\_MODEL string no 179.It HW\_NCPU integer no 180.It HW\_BYTEORDER integer no 181.It HW\_PHYSMEM integer no 182.It HW\_USERMEM integer no 183.It HW\_PAGESIZE integer no 184.\".It HW\_DISKNAMES integer no 185.\".It HW\_DISKSTATS integer no 186.El 187.Pp 188.Bl -tag -width "123456" 189.It Li HW_MACHINE 190The machine class. 191.It Li HW_MODEL 192The machine model 193.It Li HW_NCPU 194The number of cpus. 195.ne 1i 196.It Li HW_BYTEORDER 197The byteorder (4,321, or 1,234). 198.It Li HW_PHYSMEM 199The bytes of physical memory. 200.It Li HW_USERMEM 201The bytes of non-kernel memory. 202.It Li HW_PAGESIZE 203The software page size. 204.\".It Fa HW_DISKNAMES 205.\".It Fa HW_DISKSTATS 206.El 207.Sh CTL_KERN 208The string and integer information available for the CTL_KERN level 209is detailed below. 210The changeable column shows whether a process with appropriate 211privilege may change the value. 212The types of data currently available are process information, 213system vnodes, the open file entries, routing table entries, 214virtual memory statistics, load average history, and clock rate 215information. 216.Bl -column "KERNXCHOWNXRESTRICTEDXXX" "struct clockrateXXX" -offset indent 217.It Sy Pa Second level name Type Changeable 218.It KERN\_ARGMAX integer no 219.It KERN\_BOOTTIME struct timeval no 220.It KERN\_CHOWN\_RESTRICTED integer no 221.It KERN\_CLOCKRATE struct clockinfo no 222.It KERN\_FILE struct file no 223.It KERN\_HOSTID integer yes 224.It KERN\_HOSTNAME string yes 225.It KERN\_JOB\_CONTROL integer no 226.It KERN\_LINK\_MAX integer no 227.It KERN\_MAXFILES integer yes 228.It KERN\_MAXPROC integer yes 229.It KERN\_MAXVNODES integer yes 230.It KERN\_MAX\_CANON integer no 231.It KERN\_MAX\_INPUT integer no 232.It KERN\_NAME\_MAX integer no 233.It KERN\_NGROUPS integer no 234.It KERN\_NO\_TRUNC integer no 235.It KERN\_OSRELEASE string no 236.It KERN\_OSREV integer no 237.It KERN\_OSTYPE string no 238.It KERN\_PATH\_MAX integer no 239.It KERN\_PIPE\_BUF integer no 240.It KERN\_POSIX1 integer no 241.It KERN\_PROC struct proc no 242.It KERN\_PROF node not applicable 243.It KERN\_SAVED\_IDS integer no 244.It KERN\_SECURELVL integer raise only 245.It KERN\_VDISABLE integer no 246.It KERN\_VERSION string no 247.It KERN\_VNODE struct vnode no 248.El 249.ne 1i 250.Pp 251.Bl -tag -width "123456" 252.It Li KERN_ARGMAX 253The maximum bytes of argument to 254.Xr exec 2 . 255.It Li KERN_BOOTTIME 256A 257.Va struct timeval 258structure is returned. 259This structure contains the time that the system was booted. 260.It Li KERN_CHOWN_RESTRICTED 261Return 1 if appropriate privileges are required for the 262.Xr chown 2 263system call, otherwise 0. 264.It Li KERN_CLOCKRATE 265A 266.Va struct clockinfo 267structure is returned. 268This structure contains the clock, statistics clock and profiling clock 269frequencies, and the number of micro-seconds per hz tick. 270.It Li KERN_FILE 271Return the entire file table. 272The returned data consists of a single 273.Va struct filehead 274followed by an array of 275.Va struct file , 276whose size depends on the current number of such objects in the system. 277.It Li KERN_HOSTID 278Get or set the host id. 279.It Li KERN_HOSTNAME 280Get or set the hostname. 281.It Li KERN_JOB_CONTROL 282Return 1 if job control is available on this system, otherwise 0. 283.It Li KERN_LINK_MAX 284The maximum file link count. 285.It Li KERN_MAXFILES 286The maximum number of open files that may be open in the system. 287.It Li KERN_MAXPROC 288The maximum number of simultaneous processes the system will allow. 289.It Li KERN_MAXVNODES 290The maximum number of vnodes available on the system. 291.It Li KERN_MAX_CANON 292The maximum number of bytes in terminal canonical input line. 293.It Li KERN_MAX_INPUT 294The minimum maximum number of bytes for which space is available in 295a terminal input queue. 296.It Li KERN_NAME_MAX 297The maximum number of bytes in a file name. 298.It Li KERN_NGROUPS 299The maximum number of supplemental groups. 300.It Li KERN_NO_TRUNC 301Return 1 if file names longer than KERN_NAME_MAX are truncated. 302.It Li KERN_OSRELEASE 303The system release string. 304.It Li KERN_OSREV 305The system revision string. 306.It Li KERN_OSTYPE 307The system type string. 308.It Li KERN_PATH_MAX 309The maximum number of bytes in a pathname. 310.It Li KERN_PIPE_BUF 311The maximum number of bytes which will be written atomically to a pipe. 312.It Li KERN_POSIX1 313The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 314attempts to comply. 315.It Li KERN_PROC 316Return the entire process table, or a subset of it. 317An array of 318.Va struct kinfo_proc 319structures is returned, 320whose size depends on the current number of such objects in the system. 321The third and fourth level names are as follows: 322.Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent 323.It Pa Third level name Fourth level is: 324.It KERN\_PROC\_ALL None 325.It KERN\_PROC\_PID A process ID 326.It KERN\_PROC\_PGRP A process group 327.It KERN\_PROC\_TTY A tty device 328.It KERN\_PROC\_UID A user ID 329.It KERN\_PROC\_RUID A real user ID 330.El 331.It Li KERN_PROF 332Return profiling information about the kernel. 333If the kernel is not compiled for profiling, 334attempts to retrieve any of the KERN_PROF values will 335fail with EOPNOTSUPP. 336The third level names for the string and integer profiling information 337is detailed below. 338The changeable column shows whether a process with appropriate 339privilege may change the value. 340.Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent 341.It Sy Pa Third level name Type Changeable 342.It GPROF\_STATE integer yes 343.It GPROF\_COUNT u_short[\|] yes 344.It GPROF\_FROMS u_short[\|] yes 345.It GPROF\_TOS struct tostruct yes 346.It GPROF\_GMONPARAM struct gmonparam no 347.El 348.Pp 349The variables are as follows: 350.Bl -tag -width "123456" 351.It Li GPROF_STATE 352Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling 353is running or stopped. 354.It Li GPROF_COUNT 355Array of statistical program counter counts. 356.It Li GPROF_FROMS 357Array indexed by program counter of call-from points. 358.It Li GPROF_TOS 359Array of 360.Va struct tostruct 361describing destination of calls and their counts. 362.It Li GPROF_GMONPARAM 363Structure giving the sizes of the above arrays. 364.El 365.ne 1i 366.It Li KERN_SAVED_IDS 367Returns 1 if saved set-group and saved set-user ID is available. 368.It Li KERN_SECURELVL 369The system security level. 370This level may be raised by processes with appropriate privilege. 371It may only be lowered by process 1. 372.It Li KERN_VDISABLE 373Returns the terminal character disabling value. 374.It Li KERN_VERSION 375The system version string. 376.It Li KERN_VNODE 377Return the entire vnode table. 378Note, the vnode table is not necessarily a consistent snapshot of 379the system. 380The returned data consists of an array whose size depends on the 381current number of such objects in the system. 382Each element of the array contains the kernel address of a vnode 383.Va struct vnode * 384followed by the vnode itself 385.Va struct vnode . 386.El 387.Sh CTL_MACHDEP 388The set of variables defined is architecture dependent. 389Most architectures define at least the following variables. 390.Bl -column "CONSOLE_DEVICEXXX" "integerXXX" -offset indent 391.It Sy Pa Second level name Type Changeable 392.It Li CPU_CONSDEV dev_t no 393.El 394.Sh CTL_NET 395The string and integer information available for the CTL_NET level 396is detailed below. 397The changeable column shows whether a process with appropriate 398privilege may change the value. 399.Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent 400.It Sy Pa Second level name Type Changeable 401.It PF\_ROUTE routing messages no 402.It PF\_INET internet values yes 403.El 404.Pp 405.Bl -tag -width "123456" 406.It Li PF_ROUTE 407Return the entire routing table or a subset of it. 408The data is returned as a sequence of routing messages (see 409.Xr route 4 410for the header file, format and meaning). 411The length of each message is contained in the message header. 412.Pp 413The third level name is a protocol number, which is currently always 0. 414The fourth level name is an address family, which may be set to 0 to 415select all address families. 416The fifth and sixth level names are as follows: 417.Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent 418.It Pa Fifth level name Sixth level is: 419.It NET\_RT\_FLAGS rtflags 420.It NET\_RT\_DUMP None 421.It NET\_RT\_IFLIST None 422.El 423.It Li PF_INET 424Get or set various global information about the internet protocols. 425The third level name is the protocol. 426The fourth level name is the variable name. 427The currently defined protocols and names are: 428.ne 1i 429.Bl -column "Protocol nameXXXXXX" "Variable nameXXX" "integerXXX" -offset indent 430.It Pa Protocol name Variable name Type Changeable 431.It ip forwarding integer yes 432.It ip redirect integer yes 433.It ip ttl integer yes 434.It icmp maskrepl integer yes 435.It udp checksum integer yes 436.El 437.Pp 438The variables are as follows: 439.Bl -tag -width "123456" 440.It Li ip.forwarding 441Returns 1 when IP forwarding is enabled for the host, 442meaning that the host is acting as a router. 443.It Li ip.redirect 444Returns 1 when ICMP redirects may be sent by the host. 445This option is ignored unless the host is routing IP packets, 446and should normally be enabled on all systems. 447.It Li ip.ttl 448The maximum time-to-live (hop count) value for an IP packet sourced by 449the system. 450This value applies to normal transport protocols, not to ICMP. 451.It Li icmp.maskrepl 452Returns 1 if ICMP network mask requests are to be answered. 453.It Li udp.checksum 454Returns 1 when UDP checksums are being computed and checked. 455Disabling UDP checksums is strongly discouraged. 456.El 457.Sh CTL_USER 458The string and integer information available for the CTL_USER level 459is detailed below. 460The changeable column shows whether a process with appropriate 461privilege may change the value. 462.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent 463.It Sy Pa Second level name Type Changeable 464.It USER\_BC\_BASE\_MAX integer no 465.It USER\_BC\_DIM\_MAX integer no 466.It USER\_BC\_SCALE\_MAX integer no 467.It USER\_BC\_STRING\_MAX integer no 468.It USER\_COLL\_WEIGHTS\_MAX integer no 469.It USER\_CS\_PATH string no 470.It USER\_EXPR\_NEST\_MAX integer no 471.It USER\_LINE\_MAX integer no 472.It USER\_POSIX2\_CHAR\_TERM integer no 473.It USER\_POSIX2\_C\_BIND integer no 474.It USER\_POSIX2\_C\_DEV integer no 475.It USER\_POSIX2\_FORT\_DEV integer no 476.It USER\_POSIX2\_FORT\_RUN integer no 477.It USER\_POSIX2\_LOCALEDEF integer no 478.It USER\_POSIX2\_SW\_DEV integer no 479.It USER\_POSIX2\_UPE integer no 480.It USER\_POSIX2\_VERSION integer no 481.It USER\_RE\_DUP\_MAX integer no 482.It USER\_STREAM\_MAX integer no 483.It USER\_TZNAME\_MAX integer no 484.El 485.Bl -tag -width "123456" 486.Pp 487.It Li USER_BC_BASE_MAX 488The maximum ibase/obase values in the 489.Xr bc 1 490utility. 491.It Li USER_BC_DIM_MAX 492The maximum array size in the 493.Xr bc 1 494utility. 495.It Li USER_BC_SCALE_MAX 496The maximum scale value in the 497.Xr bc 1 498utility. 499.It Li USER_BC_STRING_MAX 500The maximum string length in the 501.Xr bc 1 502utility. 503.It Li USER_COLL_WEIGHTS_MAX 504The maximum number of weights that can be assigned to any entry of 505the LC_COLLATE order keyword in the locale definition file. 506.It Li USER_CS_PATH 507Return a value for the 508.Ev PATH 509environment variable that finds all the standard utilities. 510.It Li USER_EXPR_NEST_MAX 511The maximum number of expressions that can be nested within 512parenthesis by the 513.Xr expr 1 514utility. 515.It Li USER_LINE_MAX 516The maximum length in bytes of a text-processing utility's input 517line. 518.It Li USER_POSIX2_CHAR_TERM 519Return 1 if the system supports at least one terminal type capable of 520all operations described in POSIX 1003.2, otherwise 0. 521.It Li USER_POSIX2_C_BIND 522Return 1 if the system's C-language development facilities support the 523C-Language Bindings Option, otherwise 0. 524.It Li USER_POSIX2_C_DEV 525Return 1 if the system supports the C-Language Development Utilities Option, 526otherwise 0. 527.It Li USER_POSIX2_FORT_DEV 528Return 1 if the system supports the FORTRAN Development Utilities Option, 529otherwise 0. 530.It Li USER_POSIX2_FORT_RUN 531Return 1 if the system supports the FORTRAN Runtime Utilities Option, 532otherwise 0. 533.It Li USER_POSIX2_LOCALEDEF 534Return 1 if the system supports the creation of locales, otherwise 0. 535.It Li USER_POSIX2_SW_DEV 536Return 1 if the system supports the Software Development Utilities Option, 537otherwise 0. 538.It Li USER_POSIX2_UPE 539Return 1 if the system supports the User Portability Utilities Option, 540otherwise 0. 541.It Li USER_POSIX2_VERSION 542The version of POSIX 1003.2 with which the system attempts to comply. 543.It Li USER_RE_DUP_MAX 544The maximum number of repeated occurrences of a regular expression 545permitted when using interval notation. 546.ne 1i 547.It Li USER_STREAM_MAX 548The minimum maximum number of streams that a process may have open 549at any one time. 550.It Li USER_TZNAME_MAX 551The minimum maximum number of types supported for the name of a 552timezone. 553.El 554.Sh CTL_VM 555The string and integer information available for the CTL_VM level 556is detailed below. 557The changeable column shows whether a process with appropriate 558privilege may change the value. 559.Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent 560.It Sy Pa Second level name Type Changeable 561.It VM\_LOADAVG struct loadavg no 562.It VM\_METER struct vmtotal no 563.El 564.Pp 565.Bl -tag -width "123456" 566.It Li VM_LOADAVG 567Return the load average history. 568The returned data consists of a 569.Va struct loadavg . 570.It Li VM_METER 571Return the system wide virtual memory statistics. 572The returned data consists of a 573.Va struct vmtotal . 574.El 575.Sh RETURN VALUES 576If the call to 577.Nm sysctl 578is successful, the number of bytes copied out is returned. 579Otherwise \-1 is returned and 580.Va errno 581is set appropriately. 582.Sh ERRORS 583The following errors may be reported: 584.Bl -tag -width Er 585.It Bq Er EFAULT 586The buffer 587.Fa name , 588.Fa oldp , 589.Fa newp , 590or length pointer 591.Fa oldlenp 592contains an invalid address. 593.It Bq Er EINVAL 594The 595.Fa name 596array is less than two or greater than CTL_MAXNAME. 597.It Bq Er EINVAL 598A non-null 599.Fa newp 600is given and its specified length in 601.Fa newlen 602is too large or too small. 603.It Bq Er ENOMEM 604The length pointed to by 605.Fa oldlenp 606is too short to hold the requested value. 607.It Bq Er ENOTDIR 608The 609.Fa name 610array specifies an intermediate rather than terminal name. 611.It Bq Er EOPNOTSUPP 612The 613.Fa name 614array specifies a value that is unknown. 615.It Bq Er EPERM 616An attempt is made to set a read-only value. 617.It Bq Er EPERM 618A process without appropriate privilege attempts to set a value. 619.El 620.Sh FILES 621.Bl -tag -width <netinet/icmpXvar.h> -compact 622.It Pa <sys/sysctl.h> 623definitions for top level identifiers, second level kernel and hardware 624identifiers, and user level identifiers 625.It Pa <sys/socket.h> 626definitions for second level network identifiers 627.It Pa <sys/gmon.h> 628definitions for third level profiling identifiers 629.It Pa <vm/vm_param.h> 630definitions for second level virtual memory identifiers 631.It Pa <netinet/in.h> 632definitions for third level Internet identifiers and 633fourth level IP identifiers 634.It Pa <netinet/icmp_var.h> 635definitions for fourth level ICMP identifiers 636.It Pa <netinet/udp_var.h> 637definitions for fourth level UDP identifiers 638.El 639.Sh SEE ALSO 640.Xr sysctl 8 641.Sh HISTORY 642The 643.Nm sysctl 644function first appeared in 4.4BSD. 645