table of contents
KENV(2) | System Calls Manual | KENV(2) |
NAME¶
kenv
—
LIBRARY¶
Standard C Library (libc, -lc)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¶
Thekenv
() 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¶
Thekenv
() 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_SET
orKENV_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_MNAMELEN
or the value of a variable is longer thanKENV_MVALLEN
.
SEE ALSO¶
kenv(1)AUTHORS¶
This manual page was written by Chad David <davidc@FreeBSD.org>.The kenv
() system call was written by
Maxime Henrion
<mux@FreeBSD.org>.
April 17, 2002 | Linux 4.9.0-9-amd64 |