kenv(2)

NAME

kenv - kernel environment

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <kenv.h>
int
kenv(int action, const char *name, char *value, int len);

DESCRIPTION

The kenv() system call manipulates kernel environment vari

ables. It supports the well known userland actions of getting, setting

and unsetting
environment variables, as well as the ability to dump all of

the entries
in the kernel environment.

The action argument can be one of the following:

KENV_GET Returns the value associated with the named

kernel envi

ronment variable. If the variable is not

found, -1 is
returned and the global variable errno is

set to ENOENT.
Only the number of bytes available in value

are copied
out.

KENV_SET Sets or adds a new kernel environment vari

able. This

option is only available to the superuser.

KENV_UNSET Unsets the kernel environment variable name.

If the

variable does not exist, -1 is returned and

the global
variable errno is set to EINVAL. This op

tion is only
available to the superuser.

KENV_DUMP Dumps as much of the kernel environment as

will fit in

value. If value is NULL, kenv() will return

the number
of bytes required to copy out the entire en

vironment.

The name argument is the name of the environment variable to

be affected.
In the case of KENV_DUMP it is ignored.

The value argument contains either the value to set the en

vironment variable name to in the case of KENV_SET, or it points to the

location where
kenv() should copy return data to in the case of KENV_DUMP

and KENV_GET.
If value is NULL in the case of KENV_DUMP, kenv() will re

turn the number
of bytes required to copy out the entire environment.

The len argument indicates how many bytes of storage value

points to.

RETURN VALUES

The kenv() system call returns 0 if successful in the case

of KENV_SET
and KENV_UNSET, and the number of bytes copied into value in

the case of
KENV_DUMP and KENV_GET. If an error occurs, a value of -1

is returned
and the global variable errno is set to indicate the error.

ERRORS

The kenv() system call will fail if:

[EINVAL] The action argument is not a valid op

tion, or the

length of the value is less than 1 for a

KENV_SET.

[ENOENT] no value could be found for name for a

KENV_SET or

KENV_UNSET.

[EPERM] a user other than the superuser attempted

to set or

unset a kernel environment variable.

[EFAULT] bad address was encountered while at

tempting to copy

in user arguments, or copy out value(s).

[ENAMETOOLONG] the name of a variable supplied by the

user is longer

than KENV_MNAMELEN or the value of a

variable is
longer than KENV_MVALLEN.

SEE ALSO

kenv(1)

AUTHORS

This manual page was written by Chad David <davidc@FreeB

SD.org>.

The kenv() system call was written by Maxime Henrion

<mux@FreeBSD.org>.

BSD April 17, 2002

BSD