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KENV(2)			  FreeBSD System Calls Manual		       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 variables.  It sup-
     ports 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	 Get the value of the variable with the	given name.  The size
		 of the	value buffer is	given by len, which should be at least
		 KENV_MVALLEN +	1 bytes	to avoid truncation and	to ensure NUL
		 termination.

     KENV_SET	 Set or	add a variable.	 The name and value are	limited	to
		 KENV_MNAMELEN and KENV_MVALLEN	characters, respectively (not
		 including the NUL terminator.)	The len	argument indicates the
		 length	of the value and must include the NUL terminator.
		 This option is	only available to the superuser.

     KENV_UNSET	 Unset the variable with the given name.  The value and	len
		 arguments are ignored.	 This option is	only available to the
		 superuser.

     KENV_DUMP	 Dump as much of the kernel environment	as will	fit in value,
		 whose size is given in	len.  If value is NULL,	kenv() will
		 return	the number of bytes required to	copy out the entire
		 environment.  The name	is ignored.

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_GET	or
			KENV_UNSET.

     [EPERM]		A user other than the superuser	attempted to set or
			unset a	kernel environment variable.

     [EFAULT]		A bad address was encountered while attempting to copy
			in user	arguments or copy out value(s).

     [ENAMETOOLONG]	The name or the	value is longer	than KENV_MNAMELEN or
			KENV_MVALLEN characters, respectively, or len did not
			include	the NUL	terminator for a KENV_SET.

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>.

FreeBSD	Ports 11.2	       February	20, 2017	    FreeBSD Ports 11.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | AUTHORS

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