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1 perry 1 SYSCTL
2 !!!SYSCTL
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 EXAMPLE
7 RETURN VALUE
8 ERRORS
9 CONFORMING TO
10 BUGS
11 SEE ALSO
12 ----
13 !!NAME
14
15
16 sysctl - read/write system parameters
17 !!SYNOPSIS
18
19
20 __#include __
21
22
23 __#include __
24
25
26 __#include __
27
28
29 ___syscall1(int, _sysctl, struct __sysctl_args *,
30 args);__
31
32
33 __int _sysctl(struct __sysctl_args
34 *__''args''__);__
35 !!DESCRIPTION
36
37
38 The ___sysctl__ call reads and/or writes kernel
39 parameters. For example, the hostname, or the maximum number
40 of open files. The argument has the form
41
42
43 struct __sysctl_args {
44 int *name; /* integer vector describing variable */
45 int nlen; /* length of this vector */
46 void *oldval; /* 0 or address where to store old value */
47 size_t *oldlenp; /* available room for old value,
48 overwritten by actual size of old value */
49 void *newval; /* 0 or address of new value */
50 size_t newlen; /* size of new value */
51 };
52 This call does a search in a tree structure, possibly resembling a directory tree under __/proc/sys__, and if the requested item is found calls some appropriate routine to read or modify the value.
53 !!EXAMPLE
54
55
56 #include
57 !!RETURN VALUE
58
59
60 Upon successful completion, ___sysctl__ returns 0.
61 Otherwise, a value of -1 is returned and ''errno'' is set
62 to indicate the error.
63 !!ERRORS
64
65
66 __ENOTDIR__
67
68
69 ''name'' was not found.
70
71
72 __EPERM__
73
74
75 No search permission for one of the encountered
76 `directories', or no read permission where ''oldval'' was
77 nonzero, or no write permission where ''newval'' was
78 nonzero.
79
80
81 __EFAULT__
82
83
84 The invocation asked for the previous value by setting
85 ''oldval'' non-NULL, but allowed zero room in
86 ''oldlenp''.
87 !!CONFORMING TO
88
89
90 This call is Linux-specific, and should not be used in
91 programs intended to be portable. A __sysctl__ call has
92 been present in Linux since version 1.3.57. It originated in
93 4.4BSD. Only Linux has the ''/proc/sys'' mirror, and the
94 object naming schemes differ between Linux and BSD 4.4, but
95 the declaration of the sysctl(2) function is the same
96 in both.
97 !!BUGS
98
99
100 The object names vary between kernel versions. THIS MAKES
101 THIS SYSTEM CALL WORTHLESS FOR APPLICATIONS. Use the
102 ''/proc/sys'' interface instead.
103 Not all available objects are properly documented.
104 It is not yet possible to change operating system by writing
105 to ''/proc/sys/kernel/ostype''.
106 !!SEE ALSO
107
108
109 proc(5)
110 ----
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