NAME
kenv —
kernel environment
LIBRARY
library “libc”
SYNOPSIS
#include
<kenv.h>
int
kenv(int
action, const char
*name, char *value,
int len);
DESCRIPTION
Thekenv()
system call manipulates kernel environment variables. 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 environment 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 variable. 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 option 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 environment.
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 environment 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
return 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 option, 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_SETorKENV_UNSET. - [
EPERM] - a user other than the superuser attempted to set or unset a kernel environment variable.
- [
EFAULT] - bad address was encountered while attempting to copy in user arguments, or copy out value(s).
- [
ENAMETOOLONG] - the name of a variable supplied by the user is longer than
KENV_MNAMELENor the value of a variable is longer thanKENV_MVALLEN.
SEE ALSO
AUTHORS
This manual page was written by Chad David <davidc@FreeBSD.org>.
The kenv() system call was written by
Maxime Henrion
<mux@FreeBSD.org>.