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