Annotation of src/lib/libc/gen/sysctl.3, Revision 1.5
1.5 ! cgd 1: .\" $NetBSD$
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34: .\" @(#)sysctl.3 8.1 (Berkeley) 6/4/93
35: .\"
36: .Dd "June 4, 1993"
37: .Dt SYSCTL 3
38: .Os
39: .Sh NAME
40: .Nm sysctl
41: .Nd get or set system information
42: .Sh SYNOPSIS
43: .Fd #include <sys/sysctl.h>
44: .Ft int
45: .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
46: .Sh DESCRIPTION
47: The
48: .Nm sysctl
49: function retrieves system information and allows processes with
50: appropriate privileges to set system information.
51: The information available from
52: .Nm sysctl
53: consists of integers, strings, and tables.
54: Information may be retrieved and set from the command interface
55: using the
1.2 jtc 56: .Xr sysctl 8
1.1 cgd 57: utility.
58: .Pp
59: Unless explicitly noted below,
60: .Nm sysctl
61: returns a consistent snapshot of the data requested.
62: Consistency is obtained by locking the destination
63: buffer into memory so that the data may be copied out without blocking.
64: Calls to
65: .Nm sysctl
66: are serialized to avoid deadlock.
67: .Pp
68: The state is described using a ``Management Information Base'' (MIB)
69: style name, listed in
70: .Fa name ,
71: which is a
72: .Fa namelen
73: length array of integers.
74: .Pp
75: The information is copied into the buffer specified by
76: .Fa oldp .
77: The size of the buffer is given by the location specified by
78: .Fa oldlenp
79: before the call,
80: and that location gives the amount of data copied after a successful call.
81: If the amount of data available is greater
82: than the size of the buffer supplied,
83: the call supplies as much data as fits in the buffer provided
84: and returns with the error code ENOMEM.
85: If the old value is not desired,
86: .Fa oldp
87: and
88: .Fa oldlenp
89: should be set to NULL.
90: .Pp
91: The size of the available data can be determined by calling
92: .Nm sysctl
93: with a NULL parameter for
94: .Fa oldp .
95: The size of the available data will be returned in the location pointed to by
96: .Fa oldlenp .
97: For some operations, the amount of space may change often.
98: For these operations,
99: the system attempts to round up so that the returned size is
100: large enough for a call to return the data shortly thereafter.
101: .Pp
102: To set a new value,
103: .Fa newp
104: is set to point to a buffer of length
105: .Fa newlen
106: from which the requested value is to be taken.
107: If a new value is not to be set,
108: .Fa newp
109: should be set to NULL and
110: .Fa newlen
111: set to 0.
112: .Pp
113: The top level names are defined with a CTL_ prefix in
114: .Pa <sys/sysctl.h> ,
115: and are as follows.
116: The next and subsequent levels down are found in the include files
117: listed here, and described in separate sections below.
118: .Pp
119: .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
120: .It Sy Pa Name Next level names Description
121: .It CTL\_DEBUG sys/sysctl.h Debugging
122: .It CTL\_FS sys/sysctl.h File system
123: .It CTL\_HW sys/sysctl.h Generic CPU, I/O
124: .It CTL\_KERN sys/sysctl.h High kernel limits
125: .It CTL\_MACHDEP sys/sysctl.h Machine dependent
126: .It CTL\_NET sys/socket.h Networking
127: .It CTL\_USER sys/sysctl.h User-level
128: .It CTL\_VM vm/vm_param.h Virtual memory
129: .El
130: .Pp
131: For example, the following retrieves the maximum number of processes allowed
132: in the system:
133: .Bd -literal -offset indent -compact
134: int mib[2], maxproc;
135: size_t len;
136: .sp
137: mib[0] = CTL_KERN;
138: mib[1] = KERN_MAXPROC;
139: len = sizeof(maxproc);
140: sysctl(mib, 2, &maxproc, &len, NULL, 0);
141: .Ed
142: .sp
143: To retrieve the standard search path for the system utilities:
144: .Bd -literal -offset indent -compact
145: int mib[2];
146: size_t len;
147: char *p;
148: .sp
149: mib[0] = CTL_USER;
150: mib[1] = USER_CS_PATH;
151: sysctl(mib, 2, NULL, &len, NULL, 0);
152: p = malloc(len);
153: sysctl(mib, 2, p, &len, NULL, 0);
154: .Ed
155: .Sh CTL_DEBUG
156: The debugging variables vary from system to system.
157: A debugging variable may be added or deleted without need to recompile
158: .Nm sysctl
159: to know about it.
160: Each time it runs,
161: .Nm sysctl
162: gets the list of debugging variables from the kernel and
163: displays their current values.
164: The system defines twenty
165: .Ns ( Va struct ctldebug )
166: variables named
167: .Nm debug0
168: through
169: .Nm debug19 .
170: They are declared as separate variables so that they can be
171: individually initialized at the location of their associated variable.
172: The loader prevents multiple use of the same variable by issuing errors
173: if a variable is initialized in more than one place.
174: For example, to export the variable
175: .Nm dospecialcheck
176: as a debugging variable, the following declaration would be used:
177: .Bd -literal -offset indent -compact
178: int dospecialcheck = 1;
179: struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
180: .Ed
181: .Sh CTL_FS
182: There are currently no second level names for the file system.
183: .Sh CTL_HW
184: The string and integer information available for the CTL_HW level
185: is detailed below.
186: The changeable column shows whether a process with appropriate
187: privilege may change the value.
188: .Bl -column "Second level nameXXXXXX" integerXXX -offset indent
189: .It Sy Pa Second level name Type Changeable
190: .It HW\_MACHINE string no
191: .It HW\_MODEL string no
192: .It HW\_NCPU integer no
193: .It HW\_BYTEORDER integer no
194: .It HW\_PHYSMEM integer no
195: .It HW\_USERMEM integer no
196: .It HW\_PAGESIZE integer no
197: .\".It HW\_DISKNAMES integer no
198: .\".It HW\_DISKSTATS integer no
199: .El
200: .Pp
201: .Bl -tag -width "123456"
202: .It Li HW_MACHINE
203: The machine class.
204: .It Li HW_MODEL
205: The machine model
206: .It Li HW_NCPU
207: The number of cpus.
208: .It Li HW_BYTEORDER
209: The byteorder (4,321, or 1,234).
210: .It Li HW_PHYSMEM
211: The bytes of physical memory.
212: .It Li HW_USERMEM
213: The bytes of non-kernel memory.
214: .It Li HW_PAGESIZE
215: The software page size.
216: .\".It Fa HW_DISKNAMES
217: .\".It Fa HW_DISKSTATS
218: .El
219: .Sh CTL_KERN
220: The string and integer information available for the CTL_KERN level
221: is detailed below.
222: The changeable column shows whether a process with appropriate
223: privilege may change the value.
224: The types of data currently available are process information,
225: system vnodes, the open file entries, routing table entries,
226: virtual memory statistics, load average history, and clock rate
227: information.
228: .Bl -column "KERNXCHOWNXRESTRICTEDXXX" "struct clockrateXXX" -offset indent
229: .It Sy Pa Second level name Type Changeable
230: .It KERN\_ARGMAX integer no
231: .It KERN\_BOOTTIME struct timeval no
232: .It KERN\_CHOWN\_RESTRICTED integer no
233: .It KERN\_CLOCKRATE struct clockinfo no
1.3 cgd 234: .It KERN\_DOMAINNAME string yes
1.1 cgd 235: .It KERN\_FILE struct file no
236: .It KERN\_HOSTID integer yes
237: .It KERN\_HOSTNAME string yes
238: .It KERN\_JOB\_CONTROL integer no
239: .It KERN\_LINK\_MAX integer no
240: .It KERN\_MAXFILES integer yes
1.4 cgd 241: .It KERN\_MAXPARTITIONS integer no
1.1 cgd 242: .It KERN\_MAXPROC integer yes
243: .It KERN\_MAXVNODES integer yes
244: .It KERN\_MAX\_CANON integer no
245: .It KERN\_MAX\_INPUT integer no
246: .It KERN\_NAME\_MAX integer no
247: .It KERN\_NGROUPS integer no
248: .It KERN\_NO\_TRUNC integer no
249: .It KERN\_OSRELEASE string no
250: .It KERN\_OSREV integer no
251: .It KERN\_OSTYPE string no
252: .It KERN\_PATH\_MAX integer no
253: .It KERN\_PIPE\_BUF integer no
254: .It KERN\_POSIX1 integer no
255: .It KERN\_PROC struct proc no
256: .It KERN\_PROF node not applicable
257: .It KERN\_SAVED\_IDS integer no
258: .It KERN\_SECURELVL integer raise only
259: .It KERN\_VDISABLE integer no
260: .It KERN\_VERSION string no
261: .It KERN\_VNODE struct vnode no
262: .El
263: .Pp
264: .Bl -tag -width "123456"
265: .It Li KERN_ARGMAX
266: The maximum bytes of argument to
267: .Xr exec 2 .
268: .It Li KERN_BOOTTIME
269: A
270: .Va struct timeval
271: structure is returned.
272: This structure contains the time that the system was booted.
273: .It Li KERN_CHOWN_RESTRICTED
274: Return 1 if appropriate privileges are required for the
275: .Xr chown 2
276: system call, otherwise 0.
277: .It Li KERN_CLOCKRATE
278: A
279: .Va struct clockinfo
280: structure is returned.
281: This structure contains the clock, statistics clock and profiling clock
1.3 cgd 282: frequencies, the number of micro-seconds per hz tick, and the clock
283: skew rate.
284: .It Li KERN_DOMAINNAME
285: Get or set the YP domain name.
1.1 cgd 286: .It Li KERN_FILE
287: Return the entire file table.
288: The returned data consists of a single
289: .Va struct filehead
290: followed by an array of
291: .Va struct file ,
292: whose size depends on the current number of such objects in the system.
293: .It Li KERN_HOSTID
294: Get or set the host id.
295: .It Li KERN_HOSTNAME
296: Get or set the hostname.
297: .It Li KERN_JOB_CONTROL
298: Return 1 if job control is available on this system, otherwise 0.
299: .It Li KERN_LINK_MAX
300: The maximum file link count.
301: .It Li KERN_MAXFILES
302: The maximum number of open files that may be open in the system.
1.4 cgd 303: .It Li KERN_MAXPARTITIONS
304: The maximum number of partitions allowed per disk.
1.1 cgd 305: .It Li KERN_MAXPROC
306: The maximum number of simultaneous processes the system will allow.
307: .It Li KERN_MAXVNODES
308: The maximum number of vnodes available on the system.
309: .It Li KERN_MAX_CANON
310: The maximum number of bytes in terminal canonical input line.
311: .It Li KERN_MAX_INPUT
312: The minimum maximum number of bytes for which space is available in
313: a terminal input queue.
314: .It Li KERN_NAME_MAX
315: The maximum number of bytes in a file name.
316: .It Li KERN_NGROUPS
317: The maximum number of supplemental groups.
318: .It Li KERN_NO_TRUNC
319: Return 1 if file names longer than KERN_NAME_MAX are truncated.
320: .It Li KERN_OSRELEASE
321: The system release string.
322: .It Li KERN_OSREV
323: The system revision string.
324: .It Li KERN_OSTYPE
325: The system type string.
326: .It Li KERN_PATH_MAX
327: The maximum number of bytes in a pathname.
328: .It Li KERN_PIPE_BUF
329: The maximum number of bytes which will be written atomically to a pipe.
330: .It Li KERN_POSIX1
331: The version of ISO/IEC 9945 (POSIX 1003.1) with which the system
332: attempts to comply.
333: .It Li KERN_PROC
334: Return the entire process table, or a subset of it.
335: An array of
336: .Va struct kinfo_proc
337: structures is returned,
338: whose size depends on the current number of such objects in the system.
339: The third and fourth level names are as follows:
340: .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
341: .It Pa Third level name Fourth level is:
342: .It KERN\_PROC\_ALL None
343: .It KERN\_PROC\_PID A process ID
344: .It KERN\_PROC\_PGRP A process group
345: .It KERN\_PROC\_TTY A tty device
346: .It KERN\_PROC\_UID A user ID
347: .It KERN\_PROC\_RUID A real user ID
348: .El
349: .It Li KERN_PROF
350: Return profiling information about the kernel.
351: If the kernel is not compiled for profiling,
352: attempts to retrieve any of the KERN_PROF values will
353: fail with EOPNOTSUPP.
354: The third level names for the string and integer profiling information
355: is detailed below.
356: The changeable column shows whether a process with appropriate
357: privilege may change the value.
358: .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
359: .It Sy Pa Third level name Type Changeable
360: .It GPROF\_STATE integer yes
361: .It GPROF\_COUNT u_short[\|] yes
362: .It GPROF\_FROMS u_short[\|] yes
363: .It GPROF\_TOS struct tostruct yes
364: .It GPROF\_GMONPARAM struct gmonparam no
365: .El
366: .Pp
367: The variables are as follows:
368: .Bl -tag -width "123456"
369: .It Li GPROF_STATE
370: Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
371: is running or stopped.
372: .It Li GPROF_COUNT
373: Array of statistical program counter counts.
374: .It Li GPROF_FROMS
375: Array indexed by program counter of call-from points.
376: .It Li GPROF_TOS
377: Array of
378: .Va struct tostruct
379: describing destination of calls and their counts.
380: .It Li GPROF_GMONPARAM
381: Structure giving the sizes of the above arrays.
382: .El
383: .It Li KERN_SAVED_IDS
384: Returns 1 if saved set-group and saved set-user ID is available.
385: .It Li KERN_SECURELVL
386: The system security level.
387: This level may be raised by processes with appropriate privilege.
388: It may only be lowered by process 1.
389: .It Li KERN_VDISABLE
390: Returns the terminal character disabling value.
391: .It Li KERN_VERSION
392: The system version string.
393: .It Li KERN_VNODE
394: Return the entire vnode table.
395: Note, the vnode table is not necessarily a consistent snapshot of
396: the system.
397: The returned data consists of an array whose size depends on the
398: current number of such objects in the system.
399: Each element of the array contains the kernel address of a vnode
400: .Va struct vnode *
401: followed by the vnode itself
402: .Va struct vnode .
403: .El
404: .Sh CTL_MACHDEP
405: The set of variables defined is architecture dependent.
406: Most architectures define at least the following variables.
407: .Bl -column "CONSOLE_DEVICEXXX" "integerXXX" -offset indent
408: .It Sy Pa Second level name Type Changeable
409: .It Li CPU_CONSDEV dev_t no
410: .El
411: .Sh CTL_NET
412: The string and integer information available for the CTL_NET level
413: is detailed below.
414: The changeable column shows whether a process with appropriate
415: privilege may change the value.
416: .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
417: .It Sy Pa Second level name Type Changeable
418: .It PF\_ROUTE routing messages no
419: .It PF\_INET internet values yes
420: .El
421: .Pp
422: .Bl -tag -width "123456"
423: .It Li PF_ROUTE
424: Return the entire routing table or a subset of it.
425: The data is returned as a sequence of routing messages (see
426: .Xr route 4
427: for the header file, format and meaning).
428: The length of each message is contained in the message header.
429: .Pp
430: The third level name is a protocol number, which is currently always 0.
431: The fourth level name is an address family, which may be set to 0 to
432: select all address families.
433: The fifth and sixth level names are as follows:
434: .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
435: .It Pa Fifth level name Sixth level is:
436: .It NET\_RT\_FLAGS rtflags
437: .It NET\_RT\_DUMP None
438: .It NET\_RT\_IFLIST None
439: .El
440: .It Li PF_INET
441: Get or set various global information about the internet protocols.
442: The third level name is the protocol.
443: The fourth level name is the variable name.
444: The currently defined protocols and names are:
445: .Bl -column "Protocol nameXXXXXX" "Variable nameXXX" "integerXXX" -offset indent
446: .It Pa Protocol name Variable name Type Changeable
447: .It ip forwarding integer yes
448: .It ip redirect integer yes
449: .It ip ttl integer yes
450: .It icmp maskrepl integer yes
451: .It udp checksum integer yes
452: .El
453: .Pp
454: The variables are as follows:
455: .Bl -tag -width "123456"
456: .It Li ip.forwarding
457: Returns 1 when IP forwarding is enabled for the host,
458: meaning that the host is acting as a router.
459: .It Li ip.redirect
460: Returns 1 when ICMP redirects may be sent by the host.
461: This option is ignored unless the host is routing IP packets,
462: and should normally be enabled on all systems.
463: .It Li ip.ttl
464: The maximum time-to-live (hop count) value for an IP packet sourced by
465: the system.
466: This value applies to normal transport protocols, not to ICMP.
467: .It Li icmp.maskrepl
468: Returns 1 if ICMP network mask requests are to be answered.
469: .It Li udp.checksum
470: Returns 1 when UDP checksums are being computed and checked.
471: Disabling UDP checksums is strongly discouraged.
472: .El
473: .Sh CTL_USER
474: The string and integer information available for the CTL_USER level
475: is detailed below.
476: The changeable column shows whether a process with appropriate
477: privilege may change the value.
478: .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
479: .It Sy Pa Second level name Type Changeable
480: .It USER\_BC\_BASE\_MAX integer no
481: .It USER\_BC\_DIM\_MAX integer no
482: .It USER\_BC\_SCALE\_MAX integer no
483: .It USER\_BC\_STRING\_MAX integer no
484: .It USER\_COLL\_WEIGHTS\_MAX integer no
485: .It USER\_CS\_PATH string no
486: .It USER\_EXPR\_NEST\_MAX integer no
487: .It USER\_LINE\_MAX integer no
488: .It USER\_POSIX2\_CHAR\_TERM integer no
489: .It USER\_POSIX2\_C\_BIND integer no
490: .It USER\_POSIX2\_C\_DEV integer no
491: .It USER\_POSIX2\_FORT\_DEV integer no
492: .It USER\_POSIX2\_FORT\_RUN integer no
493: .It USER\_POSIX2\_LOCALEDEF integer no
494: .It USER\_POSIX2\_SW\_DEV integer no
495: .It USER\_POSIX2\_UPE integer no
496: .It USER\_POSIX2\_VERSION integer no
497: .It USER\_RE\_DUP\_MAX integer no
498: .It USER\_STREAM\_MAX integer no
499: .It USER\_TZNAME\_MAX integer no
500: .El
501: .Bl -tag -width "123456"
502: .Pp
503: .It Li USER_BC_BASE_MAX
504: The maximum ibase/obase values in the
505: .Xr bc 1
506: utility.
507: .It Li USER_BC_DIM_MAX
508: The maximum array size in the
509: .Xr bc 1
510: utility.
511: .It Li USER_BC_SCALE_MAX
512: The maximum scale value in the
513: .Xr bc 1
514: utility.
515: .It Li USER_BC_STRING_MAX
516: The maximum string length in the
517: .Xr bc 1
518: utility.
519: .It Li USER_COLL_WEIGHTS_MAX
520: The maximum number of weights that can be assigned to any entry of
521: the LC_COLLATE order keyword in the locale definition file.
522: .It Li USER_CS_PATH
523: Return a value for the
524: .Ev PATH
525: environment variable that finds all the standard utilities.
526: .It Li USER_EXPR_NEST_MAX
527: The maximum number of expressions that can be nested within
528: parenthesis by the
529: .Xr expr 1
530: utility.
531: .It Li USER_LINE_MAX
532: The maximum length in bytes of a text-processing utility's input
533: line.
534: .It Li USER_POSIX2_CHAR_TERM
535: Return 1 if the system supports at least one terminal type capable of
536: all operations described in POSIX 1003.2, otherwise 0.
537: .It Li USER_POSIX2_C_BIND
538: Return 1 if the system's C-language development facilities support the
539: C-Language Bindings Option, otherwise 0.
540: .It Li USER_POSIX2_C_DEV
541: Return 1 if the system supports the C-Language Development Utilities Option,
542: otherwise 0.
543: .It Li USER_POSIX2_FORT_DEV
544: Return 1 if the system supports the FORTRAN Development Utilities Option,
545: otherwise 0.
546: .It Li USER_POSIX2_FORT_RUN
547: Return 1 if the system supports the FORTRAN Runtime Utilities Option,
548: otherwise 0.
549: .It Li USER_POSIX2_LOCALEDEF
550: Return 1 if the system supports the creation of locales, otherwise 0.
551: .It Li USER_POSIX2_SW_DEV
552: Return 1 if the system supports the Software Development Utilities Option,
553: otherwise 0.
554: .It Li USER_POSIX2_UPE
555: Return 1 if the system supports the User Portability Utilities Option,
556: otherwise 0.
557: .It Li USER_POSIX2_VERSION
558: The version of POSIX 1003.2 with which the system attempts to comply.
559: .It Li USER_RE_DUP_MAX
560: The maximum number of repeated occurrences of a regular expression
561: permitted when using interval notation.
562: .It Li USER_STREAM_MAX
563: The minimum maximum number of streams that a process may have open
564: at any one time.
565: .It Li USER_TZNAME_MAX
566: The minimum maximum number of types supported for the name of a
567: timezone.
568: .El
569: .Sh CTL_VM
570: The string and integer information available for the CTL_VM level
571: is detailed below.
572: The changeable column shows whether a process with appropriate
573: privilege may change the value.
574: .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
575: .It Sy Pa Second level name Type Changeable
576: .It VM\_LOADAVG struct loadavg no
577: .It VM\_METER struct vmtotal no
578: .El
579: .Pp
580: .Bl -tag -width "123456"
581: .It Li VM_LOADAVG
582: Return the load average history.
583: The returned data consists of a
584: .Va struct loadavg .
585: .It Li VM_METER
586: Return the system wide virtual memory statistics.
587: The returned data consists of a
588: .Va struct vmtotal .
589: .El
590: .Sh RETURN VALUES
591: If the call to
592: .Nm sysctl
593: is successful, 0 is returned.
594: Otherwise \-1 is returned and
595: .Va errno
596: is set appropriately.
597: .Sh ERRORS
598: The following errors may be reported:
599: .Bl -tag -width Er
600: .It Bq Er EFAULT
601: The buffer
602: .Fa name ,
603: .Fa oldp ,
604: .Fa newp ,
605: or length pointer
606: .Fa oldlenp
607: contains an invalid address.
608: .It Bq Er EINVAL
609: The
610: .Fa name
611: array is less than two or greater than CTL_MAXNAME.
612: .It Bq Er EINVAL
613: A non-null
614: .Fa newp
615: is given and its specified length in
616: .Fa newlen
617: is too large or too small.
618: .It Bq Er ENOMEM
619: The length pointed to by
620: .Fa oldlenp
621: is too short to hold the requested value.
622: .It Bq Er ENOTDIR
623: The
624: .Fa name
625: array specifies an intermediate rather than terminal name.
626: .It Bq Er EOPNOTSUPP
627: The
628: .Fa name
629: array specifies a value that is unknown.
630: .It Bq Er EPERM
631: An attempt is made to set a read-only value.
632: .It Bq Er EPERM
633: A process without appropriate privilege attempts to set a value.
634: .El
635: .Sh FILES
636: .Bl -tag -width <netinet/icmpXvar.h> -compact
637: .It Pa <sys/sysctl.h>
638: definitions for top level identifiers, second level kernel and hardware
639: identifiers, and user level identifiers
640: .It Pa <sys/socket.h>
641: definitions for second level network identifiers
642: .It Pa <sys/gmon.h>
643: definitions for third level profiling identifiers
644: .It Pa <vm/vm_param.h>
645: definitions for second level virtual memory identifiers
646: .It Pa <netinet/in.h>
647: definitions for third level Internet identifiers and
648: fourth level IP identifiers
649: .It Pa <netinet/icmp_var.h>
650: definitions for fourth level ICMP identifiers
651: .It Pa <netinet/udp_var.h>
652: definitions for fourth level UDP identifiers
653: .El
654: .Sh SEE ALSO
655: .Xr sysctl 8
656: .Sh HISTORY
657: The
658: .Nm sysctl
659: function first appeared in 4.4BSD.
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