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GETENV(9)		 BSD Kernel Developer's	Manual		     GETENV(9)

     freeenv, kern_getenv, getenv_int, getenv_long, getenv_string,
     getenv_quad, getenv_uint, getenv_ulong, getenv_bool, getenv_is_true,
     getenv_is_false, kern_setenv, testenv, kern_unsetenv -- kernel environ-
     ment variable functions

     #include <sys/param.h>
     #include <sys/systm.h>

     freeenv(char *env);

     char *
     kern_getenv(const char *name);

     getenv_int(const char *name, int *data);

     getenv_long(const char *name, long	*data);

     getenv_string(const char *name, char *data, int size);

     getenv_quad(const char *name, quad_t *data);

     getenv_uint(const char *name, unsigned int	*data);

     getenv_ulong(const	char *name, unsigned long *data);

     getenv_bool(const char *name, bool	*data);

     getenv_is_true(const char *name);

     getenv_is_false(const char	*name);

     kern_setenv(const char *name, const char *value);

     testenv(const char	*name);

     kern_unsetenv(const char *name);

     These functions set, unset, fetch,	and parse variables from the kernel's

     The kern_getenv() function	obtains	the current value of the kernel	envi-
     ronment variable name and returns a pointer to the	string value.  The
     caller should not modify the string pointed to by the return value.  The
     kern_getenv() function may	allocate temporary storage, so the freeenv()
     function must be called to	release	any allocated resources	when the value
     returned by kern_getenv() is no longer needed.

     The freeenv() function is used to release the resources allocated by a
     previous call to kern_getenv().  The env argument passed to freeenv() is
     the pointer returned by the earlier call to kern_getenv().	 Like free(3),
     the env argument can be NULL, in which case no action occurs.

     The kern_setenv() function	inserts	or resets the kernel environment vari-
     able name to value.  If the variable name already exists, its value is
     replaced.	This function can fail if an internal limit on the number of
     environment variables is exceeded.

     The kern_unsetenv() function deletes the kernel environment variable

     The testenv() function is used to determine if a kernel environment vari-
     able exists.  It returns a	non-zero value if the variable name exists and
     zero if it	does not.

     The getenv_int(), getenv_long(), getenv_quad(), getenv_uint(), and
     getenv_ulong() functions look for a kernel	environment variable name and
     parse it as a signed integer, long	integer, signed	64-bit integer,	un-
     signed integer, or	an unsigned long integer, respectively.	 These func-
     tions fail	and return zero	if name	does not exist or if any invalid char-
     acters are	present	in its value.  On success, these function store	the
     parsed value in the integer variable pointed to by	data.  If the parsed
     value overflows the integer type, a truncated value is stored in data and
     zero is returned.	If the value begins with a prefix of "0x" it is	inter-
     preted as hexadecimal.  If	it begins with a prefix	of "0" it is inter-
     preted as octal.  Otherwise, the value is interpreted as decimal.	The
     value may contain a single	character suffix specifying a unit for the
     value.  The interpreted value is multiplied by the	unit's magnitude be-
     fore being	returned.  The following unit suffixes are supported:

	   Unit	   Magnitude
	   k	   2^10
	   m	   2^20
	   g	   2^30
	   t	   2^40

     The getenv_string() function stores a copy	of the kernel environment
     variable name in the buffer described by data and size.  If the variable
     does not exist, zero is returned.	If the variable	exists,	up to size - 1
     characters	of its value are copied	to the buffer pointed to by data fol-
     lowed by a	null character and a non-zero value is returned.

     The getenv_bool() function	interprets the value of	the kernel environment
     variable name as a	boolean	value by performing a case-insensitive compar-
     ison against the strings "1", "0",	"true",	and "false".  If the environ-
     ment variable exists and has a valid boolean value, then that value will
     be	copied to the variable pointed to by data.  If the environment vari-
     able exists but is	not a boolean value, then a warning will be printed to
     the kernel	message	buffer.	 The getenv_is_true() and getenv_is_false()
     functions are wrappers around getenv_bool() that simplify testing for a
     desired boolean value.

     The kern_getenv() function	returns	a pointer to an	environment variable's
     value on success or NULL if the variable does not exist.

     The kern_setenv() and kern_unsetenv() functions return zero on success
     and -1 on failure.

     The testenv() function returns zero if the	specified environment variable
     does not exist and	a non-zero value if it does exist.

     The getenv_int(), getenv_long(), getenv_string(), getenv_quad(),
     getenv_uint(), getenv_ulong(), and	getenv_bool() functions	return a non-
     zero value	on success and zero on failure.

     The getenv_is_true() and getenv_is_false()	functions return true if the
     specified environment variable exists and its value matches the desired
     boolean condition,	and false otherwise.

BSD			      September	21, 2020			   BSD


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