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GETENV(9) FreeBSD Kernel Developer's Manual GETENV(9)
NAME
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 environment
variable functions
SYNOPSIS
#include <sys/param.h>
#include <sys/systm.h>
void
freeenv(char *env);
char *
kern_getenv(const char *name);
int
getenv_int(const char *name, int *data);
int
getenv_long(const char *name, long *data);
int
getenv_string(const char *name, char *data, int size);
int
getenv_quad(const char *name, quad_t *data);
int
getenv_uint(const char *name, unsigned int *data);
int
getenv_ulong(const char *name, unsigned long *data);
int
getenv_bool(const char *name, bool *data);
bool
getenv_is_true(const char *name);
bool
getenv_is_false(const char *name);
int
kern_setenv(const char *name, const char *value);
int
testenv(const char *name);
int
kern_unsetenv(const char *name);
DESCRIPTION
These functions set, unset, fetch, and parse variables from the kernel's
environment.
The kern_getenv() function obtains the current value of the kernel
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
variable 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
name.
The testenv() function is used to determine if a kernel environment
variable 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,
unsigned integer, or an unsigned long integer, respectively. These
functions fail and return zero if name does not exist or if any invalid
characters 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 interpreted as hexadecimal. If it begins with a prefix of "0" it is
interpreted 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
before 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
followed 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
comparison against the strings "1", "0", "true", and "false". If the
environment variable exists and has a valid boolean value, then that
value will be copied to the variable pointed to by data. If the
environment variable 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.
RETURN VALUES
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 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.
FreeBSD 14.0-RELEASE-p11 September 21, 2020 FreeBSD 14.0-RELEASE-p11