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    The following form allows you to view linux man pages.

    Command:

    _sysctl

    
    
    

    SYNOPSIS

           #include <unistd.h>
           #include <linux/sysctl.h>
    
           int _sysctl(struct __sysctl_args *args);
    
           Note: There is no glibc wrapper for this system call; see NOTES.
    
    
    

    DESCRIPTION

           Do not use this system call!  See NOTES.
    
           The _sysctl() call reads and/or writes kernel parameters.  For example,
           the hostname, or the maximum number of open files.   The  argument  has
           the form
    
               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 */
               };
    
           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.
    
    
    

    RETURN VALUE

           Upon successful completion, _sysctl() returns 0.  Otherwise, a value of
           -1 is returned and errno is set to indicate the error.
    
    
    

    ERRORS

           EFAULT The invocation asked for the previous value  by  setting  oldval
                  non-NULL, but allowed zero room in oldlenp.
    
           ENOTDIR
                  name was not found.
    
           EACCES, EPERM
                  No  search  permission for one of the encountered "directories",
                  or no read permission where oldval was nonzero, or no write per-
                  mission where newval was nonzero.
    
    
    

    CONFORMING TO

           This  call  is  Linux-specific,  and  should  not  be  used in programs
           intended to be portable.  A sysctl() call has  been  present  in  Linux
           since  version  1.3.57.   It  originated in 4.4BSD.  Only Linux has the
           /proc/sys mirror, and the object naming schemes  differ  between  Linux
           and 4.4BSD, but the declaration of the sysctl() function is the same in
           both.
           worthless for applications.
    
           Not all available objects are properly documented.
    
           It  is  not  yet  possible  to  change  operating  system by writing to
           /proc/sys/kernel/ostype.
    
    
    

    EXAMPLE

           #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);
           }
    
    
    

    SEE ALSO

           proc(5)
    
    
    

    Linux 2012-12-22 SYSCTL(2)

    
    
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