+++ /dev/null
-.\" Copyright (C) 1996 Andries Brouwer (aeb@cwi.nl)
-.\"
-.\" %%%LICENSE_START(VERBATIM)
-.\" Permission is granted to make and distribute verbatim copies of this
-.\" manual provided the copyright notice and this permission notice are
-.\" preserved on all copies.
-.\"
-.\" Permission is granted to copy and distribute modified versions of this
-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
-.\" permission notice identical to this one.
-.\"
-.\" Since the Linux kernel and libraries are constantly changing, this
-.\" manual page may be incorrect or out-of-date. The author(s) assume no
-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
-.\" which is licensed free of charge, as they might when working
-.\" professionally.
-.\"
-.\" Formatted or processed versions of this manual, if unaccompanied by
-.\" the source, must acknowledge the copyright and authors of this work.
-.\" %%%LICENSE_END
-.\"
-.\" Written 11 April 1996 by Andries Brouwer <aeb@cwi.nl>
-.\" 960412: Added comments from Stephen Tweedie
-.\" Modified Tue Oct 22 22:28:41 1996 by Eric S. Raymond <esr@thyrsus.com>
-.\" Modified Mon Jan 5 20:31:04 1998 by aeb.
-.\"
-.TH SYSCTL 2 2012-12-22 "Linux" "Linux Programmer's Manual"
-.SH NAME
-sysctl \- read/write system parameters
-.SH SYNOPSIS
-.nf
-.B #include <unistd.h>
-.br
-.B #include <linux/sysctl.h>
-.sp
-.BI "int _sysctl(struct __sysctl_args *" args );
-.fi
-
-.IR Note :
-There is no glibc wrapper for this system call; see NOTES.
-.SH DESCRIPTION
-.B Do not use this system call!
-See NOTES.
-
-The
-.BR _sysctl ()
-call reads and/or writes kernel parameters.
-For example, the hostname,
-or the maximum number of open files.
-The argument has the form
-.PP
-.in +4n
-.nf
-struct __sysctl_args {
- int *name; /* integer vector describing variable */
- int nlen; /* length of this vector */
- void *oldval; /* 0 or address where to store old value */
- size_t *oldlenp; /* available room for old value,
- overwritten by actual size of old value */
- void *newval; /* 0 or address of new value */
- size_t newlen; /* size of new value */
-};
-.fi
-.in
-.PP
-This call does a search in a tree structure, possibly resembling
-a directory tree under
-.IR /proc/sys ,
-and if the requested item is found calls some appropriate routine
-to read or modify the value.
-.SH RETURN VALUE
-Upon successful completion,
-.BR _sysctl ()
-returns 0.
-Otherwise, a value of \-1 is returned and
-.I errno
-is set to indicate the error.
-.SH ERRORS
-.TP
-.B EFAULT
-The invocation asked for the previous value by setting
-.I oldval
-non-NULL, but allowed zero room in
-.IR oldlenp .
-.TP
-.B ENOTDIR
-.I name
-was not found.
-.TP
-.BR EACCES ", " EPERM
-No search permission for one of the encountered "directories",
-or no read permission where
-.I oldval
-was nonzero, or no write permission where
-.I newval
-was nonzero.
-.SH CONFORMING TO
-This call is Linux-specific, and should not be used in programs
-intended to be portable.
-A
-.BR sysctl ()
-call has been present in Linux since version 1.3.57.
-It originated in
-4.4BSD.
-Only Linux has the
-.I /proc/sys
-mirror, and the object naming schemes differ between Linux and 4.4BSD,
-but the declaration of the
-.BR sysctl ()
-function is the same in both.
-.SH NOTES
-Glibc does not provide a wrapper for this system call; call it using
-.BR syscall (2).
-Or rather...
-.I don't
-call it:
-use of this system call has long been discouraged,
-and it is so unloved that
-\fBit is likely to disappear in a future kernel version\fP.
-.\" See http://lwn.net/Articles/247243/
-Since Linux 2.6.24,
-uses of this system call result in warnings in the kernel log.
-.\" Though comments in suggest that it is needed by old glibc binaries,
-.\" so maybe it's not going away.
-Remove it from your programs now; use the
-.I /proc/sys
-interface instead.
-
-This system call is available only if the kernel was configured with the
-.B CONFIG_SYSCTL_SYSCALL
-option.
-.SH BUGS
-The object names vary between kernel versions,
-making this system call worthless for applications.
-.PP
-Not all available objects are properly documented.
-.PP
-It is not yet possible to change operating system by writing to
-.IR /proc/sys/kernel/ostype .
-.SH EXAMPLE
-.nf
-#define _GNU_SOURCE
-#include <unistd.h>
-#include <sys/syscall.h>
-#include <string.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <linux/sysctl.h>
-
-int _sysctl(struct __sysctl_args *args );
-
-#define OSNAMESZ 100
-
-int
-main(void)
-{
- struct __sysctl_args args;
- char osname[OSNAMESZ];
- size_t osnamelth;
- int name[] = { CTL_KERN, KERN_OSTYPE };
-
- memset(&args, 0, sizeof(struct __sysctl_args));
- args.name = name;
- args.nlen = sizeof(name)/sizeof(name[0]);
- args.oldval = osname;
- args.oldlenp = &osnamelth;
-
- osnamelth = sizeof(osname);
-
- if (syscall(SYS__sysctl, &args) == \-1) {
- perror("_sysctl");
- exit(EXIT_FAILURE);
- }
- printf("This machine is running %*s\\n", osnamelth, osname);
- exit(EXIT_SUCCESS);
-}
-.fi
-.SH SEE ALSO
-.BR proc (5)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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