Provided by: freebsd-manpages_12.2-1_all 
NAME
nvlist_create, nvlist_destroy, nvlist_error, nvlist_set_error, nvlist_empty, nvlist_flags,
nvlist_exists, nvlist_free, nvlist_clone, nvlist_dump, nvlist_fdump, nvlist_size,
nvlist_pack, nvlist_unpack, nvlist_send, nvlist_recv, nvlist_xfer, nvlist_in_array,
nvlist_next, nvlist_add, nvlist_move, nvlist_get, nvlist_take, nvlist_append — library for
name/value pairs
LIBRARY
library “libnv”
SYNOPSIS
#include <sys/nv.h>
nvlist_t *
nvlist_create(int flags);
void
nvlist_destroy(nvlist_t *nvl);
int
nvlist_error(const nvlist_t *nvl);
void
nvlist_set_error(nvlist_t *nvl, int error);
bool
nvlist_empty(const nvlist_t *nvl);
int
nvlist_flags(const nvlist_t *nvl);
bool
nvlist_in_array(const nvlist_t *nvl);
nvlist_t *
nvlist_clone(const nvlist_t *nvl);
void
nvlist_dump(const nvlist_t *nvl, int fd);
void
nvlist_fdump(const nvlist_t *nvl, FILE *fp);
size_t
nvlist_size(const nvlist_t *nvl);
void *
nvlist_pack(const nvlist_t *nvl, size_t *sizep);
nvlist_t *
nvlist_unpack(const void *buf, size_t size, int flags);
int
nvlist_send(int sock, const nvlist_t *nvl);
nvlist_t *
nvlist_recv(int sock, int flags);
nvlist_t *
nvlist_xfer(int sock, nvlist_t *nvl, int flags);
const char *
nvlist_next(const nvlist_t *nvl, int *typep, void **cookiep);
bool
nvlist_exists(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_type(const nvlist_t *nvl, const char *name, int type);
bool
nvlist_exists_null(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_bool(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_number(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_string(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_nvlist(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_descriptor(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_binary(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_bool_array(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_number_array(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_string_array(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_nvlist_array(const nvlist_t *nvl, const char *name);
bool
nvlist_exists_descriptor_array(const nvlist_t *nvl, const char *name);
void
nvlist_add_null(nvlist_t *nvl, const char *name);
void
nvlist_add_bool(nvlist_t *nvl, const char *name, bool value);
void
nvlist_add_number(nvlist_t *nvl, const char *name, uint64_t value);
void
nvlist_add_string(nvlist_t *nvl, const char *name, const char *value);
void
nvlist_add_stringf(nvlist_t *nvl, const char *name, const char *valuefmt, ...);
void
nvlist_add_stringv(nvlist_t *nvl, const char *name, const char *valuefmt, va_list valueap);
void
nvlist_add_nvlist(nvlist_t *nvl, const char *name, const nvlist_t *value);
void
nvlist_add_descriptor(nvlist_t *nvl, const char *name, int value);
void
nvlist_add_binary(nvlist_t *nvl, const char *name, const void *value, size_t size);
void
nvlist_add_bool_array(nvlist_t *nvl, const char *name, const bool *value, size_t nitems);
void
nvlist_add_number_array(nvlist_t *nvl, const char *name, const uint64_t *value,
size_t nitems);
void
nvlist_add_string_array(nvlist_t *nvl, const char *name, const char * const * value,
size_t nitems);
void
nvlist_add_nvlist_array(nvlist_t *nvl, const char *name, const nvlist_t * const * value,
size_t nitems);
void
nvlist_add_descriptor_array(nvlist_t *nvl, const char *name, const int *value,
size_t nitems);
void
nvlist_move_string(nvlist_t *nvl, const char *name, char *value);
void
nvlist_move_nvlist(nvlist_t *nvl, const char *name, nvlist_t *value);
void
nvlist_move_descriptor(nvlist_t *nvl, const char *name, int value);
void
nvlist_move_binary(nvlist_t *nvl, const char *name, void *value, size_t size);
void
nvlist_move_bool_array(nvlist_t *nvl, const char *name, bool *value, size_t nitems);
void
nvlist_move_number_array(nvlist_t *nvl, const char *name, uint64_t *value, size_t nitems);
void
nvlist_move_string_array(nvlist_t *nvl, const char *name, char **value, size_t nitems);
void
nvlist_move_nvlist_array(nvlist_t *nvl, const char *name, nvlist_t **value, size_t nitems);
void
nvlist_move_descriptor_array(nvlist_t *nvl, const char *name, int *value, size_t nitems);
bool
nvlist_get_bool(const nvlist_t *nvl, const char *name);
uint64_t
nvlist_get_number(const nvlist_t *nvl, const char *name);
const char *
nvlist_get_string(const nvlist_t *nvl, const char *name);
const nvlist_t *
nvlist_get_nvlist(const nvlist_t *nvl, const char *name);
int
nvlist_get_descriptor(const nvlist_t *nvl, const char *name);
const void *
nvlist_get_binary(const nvlist_t *nvl, const char *name, size_t *sizep);
const bool *
nvlist_get_bool_array(const nvlist_t *nvl, const char *name, size_t *nitems);
const uint64_t *
nvlist_get_number_array(const nvlist_t *nvl, const char *name, size_t *nitems);
const char * const *
nvlist_get_string_array(const nvlist_t *nvl, const char *name, size_t *nitems);
const nvlist_t * const *
nvlist_get_nvlist_array(const nvlist_t *nvl, const char *name, size_t *nitems);
const int *
nvlist_get_descriptor_array(const nvlist_t *nvl, const char *name, size_t *nitems);
const nvlist_t *
nvlist_get_parent(const nvlist_t *nvl, void **cookiep);
const nvlist_t *
nvlist_get_array_next(const nvlist_t *nvl);
const nvlist_t *
nvlist_get_pararr(const nvlist_t *nvl, void **cookiep);
bool
nvlist_take_bool(nvlist_t *nvl, const char *name);
uint64_t
nvlist_take_number(nvlist_t *nvl, const char *name);
char *
nvlist_take_string(nvlist_t *nvl, const char *name);
nvlist_t *
nvlist_take_nvlist(nvlist_t *nvl, const char *name);
int
nvlist_take_descriptor(nvlist_t *nvl, const char *name);
void *
nvlist_take_binary(nvlist_t *nvl, const char *name, size_t *sizep);
bool *
nvlist_take_bool_array(nvlist_t *nvl, const char *name, size_t *nitems);
uint64_t **
nvlist_take_number_array(nvlist_t *nvl, const char *name, size_t *nitems);
char **
nvlist_take_string_array(nvlist_t *nvl, const char *name, size_t *nitems);
nvlist_t **
nvlist_take_nvlist_array(nvlist_t *nvl, const char *name, size_t *nitems);
int *
nvlist_take_descriptor_array(nvlist_t *nvl, const char *name, size_t *nitems);
void
nvlist_append_bool_array(nvlist_t *nvl, const char *name, const bool value);
void
nvlist_append_number_array(nvlist_t *nvl, const char *name, const uint64_t value);
void
nvlist_append_string_array(nvlist_t *nvl, const char *name, const char * const value);
void
nvlist_append_nvlist_array(nvlist_t *nvl, const char *name, const nvlist_t * const value);
void
nvlist_append_descriptor_array(nvlist_t *nvl, const char *name, int value);
void
nvlist_free(nvlist_t *nvl, const char *name);
void
nvlist_free_type(nvlist_t *nvl, const char *name, int type);
void
nvlist_free_null(nvlist_t *nvl, const char *name);
void
nvlist_free_bool(nvlist_t *nvl, const char *name);
void
nvlist_free_number(nvlist_t *nvl, const char *name);
void
nvlist_free_string(nvlist_t *nvl, const char *name);
void
nvlist_free_nvlist(nvlist_t *nvl, const char *name);
void
nvlist_free_descriptor(nvlist_t *nvl, const char *name);
void
nvlist_free_binary(nvlist_t *nvl, const char *name);
void
nvlist_free_bool_array(nvlist_t *nvl, const char *name);
void
nvlist_free_number_array(nvlist_t *nvl, const char *name);
void
nvlist_free_string_array(nvlist_t *nvl, const char *name);
void
nvlist_free_nvlist_array(nvlist_t *nvl, const char *name);
void
nvlist_free_descriptor_array(nvlist_t *nvl, const char *name);
DESCRIPTION
The libnv library allows to easily manage name value pairs as well as send and receive them
over sockets. A group (list) of name value pairs is called an nvlist. The API supports the
following data types:
null (NV_TYPE_NULL)
There is no data associated with the name.
bool (NV_TYPE_BOOL)
The value can be either true or false.
number (NV_TYPE_NUMBER)
The value is a number stored as uint64_t.
string (NV_TYPE_STRING)
The value is a C string.
nvlist (NV_TYPE_NVLIST)
The value is a nested nvlist.
descriptor (NV_TYPE_DESCRIPTOR)
The value is a file descriptor. Note that file descriptors can be sent only over
unix(4) domain sockets.
binary (NV_TYPE_BINARY)
The value is a binary buffer.
bool array (NV_TYPE_BOOL_ARRAY)
The value is an array of boolean values.
number array (NV_TYPE_NUMBER_ARRAY)
The value is an array of numbers, each stored as uint64_t.
string array (NV_TYPE_STRING_ARRAY)
The value is an array of C strings.
nvlist array (NV_TYPE_NVLIST_ARRAY)
The value is an array of nvlists. When an nvlist is added to an array, it becomes
part of the primary nvlist. Traversing these arrays can be done using the
nvlist_get_array_next() and nvlist_get_pararr() functions.
descriptor array (NV_TYPE_DESCRIPTOR_ARRAY)
The value is an array of files descriptors.
The nvlist_create() function allocates memory and initializes an nvlist.
The following flag can be provided:
NV_FLAG_IGNORE_CASE Perform case-insensitive lookups of provided names.
NV_FLAG_NO_UNIQUE Names in the nvlist do not have to be unique.
The nvlist_destroy() function destroys the given nvlist. Function does nothing if NULL
nvlist is provided. Function never modifies the errno global variable.
The nvlist_error() function returns any error value that the nvlist accumulated. If the
given nvlist is NULL the ENOMEM error will be returned.
The nvlist_set_error() function sets an nvlist to be in the error state. Subsequent calls
to nvlist_error() will return the given error value. This function cannot be used to clear
the error state from an nvlist. This function does nothing if the nvlist is already in the
error state.
The nvlist_empty() function returns true if the given nvlist is empty and false otherwise.
The nvlist must not be in error state.
The nvlist_flags() function returns flags used to create the nvlist with the nvlist_create()
function.
The nvlist_in_array() function returns true if nvl is part of an array that is a member of
another nvlist.
The nvlist_clone() functions clones the given nvlist. The clone shares no resources with
its origin. This also means that all file descriptors that are part of the nvlist will be
duplicated with the dup(2) system call before placing them in the clone.
The nvlist_dump() dumps nvlist content for debugging purposes to the given file descriptor
fd.
The nvlist_fdump() dumps nvlist content for debugging purposes to the given file stream fp.
The nvlist_size() function returns the size of the given nvlist after converting it to
binary buffer with the nvlist_pack() function.
The nvlist_pack() function converts the given nvlist to a binary buffer. The function
allocates memory for the buffer, which should be freed with the free(3) function. If the
sizep argument is not NULL, the size of the buffer will be stored there. The function
returns NULL in case of an error (allocation failure). If the nvlist contains any file
descriptors NULL will be returned. The nvlist must not be in error state.
The nvlist_unpack() function converts the given buffer to the nvlist. The flags argument
defines what type of the top level nvlist is expected to be. Flags are set up using the
nvlist_create() function. If the nvlist flags do not match the flags passed to
nvlist_unpack(), the nvlist will not be returned. Every nested nvlist list should be
checked using nvlist_flags() function. The function returns NULL in case of an error.
The nvlist_send() function sends the given nvlist over the socket given by the sock
argument. Note that nvlist that contains file descriptors can only be send over unix(4)
domain sockets.
The nvlist_recv() function receives nvlist over the socket given by the sock argument. The
flags argument defines what type of the top level nvlist is expected to be. Flags are set
up using the nvlist_create() function. If the nvlist flags do not match the flags passed to
nvlist_recv(), the nvlist will not be returned. Every nested nvlist list should be checked
using nvlist_flags() function.
The nvlist_xfer() function sends the given nvlist over the socket given by the sock argument
and receives nvlist over the same socket. The flags argument defines what type of the top
level nvlist is expected to be. Flags are set up using the nvlist_create() function. If
the nvlist flags do not match the flags passed to nvlist_xfer(), the nvlist will not be
returned. Every nested nvlist list should be checked using nvlist_flags() function. The
given nvlist is always destroyed.
The nvlist_next() function iterates over the given nvlist returning names and types of
subsequent elements. The cookiep argument allows the function to figure out which element
should be returned next. The *cookiep should be set to NULL for the first call and should
not be changed later. Returning NULL means there are no more elements on the nvlist. The
typep argument can be NULL. Elements may not be removed from the nvlist while traversing
it. The nvlist must not be in error state. Note that nvlist_next() will handle cookiep
being set to NULL. In this case first element is returned or NULL if nvlist is empty. This
behavior simplifies removing the first element from the list.
The nvlist_exists() function returns true if element of the given name exists (besides of
its type) or false otherwise. The nvlist must not be in error state.
The nvlist_exists_type() function returns true if element of the given name and the given
type exists or false otherwise. The nvlist must not be in error state.
The nvlist_exists_null(), nvlist_exists_bool(), nvlist_exists_number(),
nvlist_exists_string(), nvlist_exists_nvlist(), nvlist_exists_descriptor(),
nvlist_exists_binary(), nvlist_exists_bool_array(), nvlist_exists_number_array(),
nvlist_exists_string_array(), nvlist_exists_nvlist_array(), nvlist_exists_descriptor_array()
functions return true if element of the given name and the given type determined by the
function name exists or false otherwise. The nvlist must not be in error state.
The nvlist_add_null(), nvlist_add_bool(), nvlist_add_number(), nvlist_add_string(),
nvlist_add_stringf(), nvlist_add_stringv(), nvlist_add_nvlist(), nvlist_add_descriptor(),
nvlist_add_binary(), nvlist_add_bool_array(), nvlist_add_number_array(),
nvlist_add_string_array(), nvlist_add_nvlist_array(), nvlist_add_descriptor_array()
functions add element to the given nvlist. When adding string or binary buffer the
functions will allocate memory and copy the data over. When adding nvlist, the nvlist will
be cloned and clone will be added. When adding descriptor, the descriptor will be
duplicated using the dup(2) system call and the new descriptor will be added. The array
functions will fail if there are any NULL elements in the array, or if the array pointer is
NULL. If an error occurs while adding new element, internal error is set which can be
examined using the nvlist_error() function.
The nvlist_move_string(), nvlist_move_nvlist(), nvlist_move_descriptor(),
nvlist_move_binary(), nvlist_move_bool_array(), nvlist_move_number_array(),
nvlist_move_string_array(), nvlist_move_nvlist_array(), nvlist_move_descriptor_array()
functions add new element to the given nvlist, but unlike nvlist_add_<type>() functions they
will consume the given resource. In the case of strings, descriptors, or nvlists every
elements must be unique, or it could cause a double free. The array functions will fail if
there are any NULL elements, or if the array pointer is NULL. If an error occurs while
adding new element, the resource is destroyed and internal error is set which can be
examined using the nvlist_error() function.
The nvlist_get_bool(), nvlist_get_number(), nvlist_get_string(), nvlist_get_nvlist(),
nvlist_get_descriptor(), nvlist_get_binary(), nvlist_get_bool_array(),
nvlist_get_number_array(), nvlist_get_string_array(), nvlist_get_nvlist_array(),
nvlist_get_descriptor_array() functions return the value that corresponds to the given key
name. In the case of strings, nvlists, descriptors, binary, or arrays, the returned
resource should not be modified - they still belong to the nvlist. If an element of the
given name does not exist, the program will be aborted. To avoid this, the caller should
check for the existence of the name before trying to obtain the value, or use the dnvlist(3)
extension, which can provide a default value in the case of a missing element. The nvlist
must not be in error state.
The nvlist_get_parent() function returns the parent nvlist of the nested nvlist.
The nvlist_get_array_next() function returns the next element from the array or NULL if the
nvlist is not in array or it is the last element. Note that nvlist_get_array_next() only
works if you added the nvlist array using the nvlist_move_nvlist_array() or
nvlist_add_nvlist_array() functions.
The nvlist_get_pararr() function returns the next element in the array, or if not available
the parent of the nested nvlist.
The nvlist_take_bool(), nvlist_take_number(), nvlist_take_string(), nvlist_take_nvlist(),
nvlist_take_descriptor(), nvlist_take_binary(), nvlist_take_bool_array(),
nvlist_take_number_array(), nvlist_take_string_array(), nvlist_take_nvlist_array(),
nvlist_take_descriptor_array() functions return value associated with the given name and
remove the element from the nvlist. In case of string and binary values, the caller is
responsible for free returned memory using the free(3) function. In case of nvlist, the
caller is responsible for destroying returned nvlist using the nvlist_destroy() function.
In case of descriptor, the caller is responsible for closing returned descriptor using the
close(2) system call. If an element of the given name does not exist, the program will be
aborted. To avoid that the caller should check for the existence of the given name before
trying to obtain the value, or use the dnvlist(3) extension, which can provide a default
value in the case of a missing element. In the case of an array of strings or binary
values, the caller is responsible for freeing every element of the array using the free(3)
function. In the case of an array of nvlists, the caller is responsible for destroying
every element of array using the nvlist_destroy() function. In the case of descriptors, the
caller is responsible for closing every element of array using the close(2) system call. In
every case involving an array, the caller must also free the pointer to the array using the
free(3) function. The nvlist must not be in error state.
The nvlist_append_bool_array(), nvlist_append_number_array(), nvlist_append_string_array(),
nvlist_append_nvlist_array(), nvlist_append_descriptor_array() functions append an element
to the existing array using the same semantics as the add functions (i.e. the element will
be copied when applicable). If the array for a given key does not exist, then it will be
created as if using the nvlist_add_<type>_array() function. The internal error is set on
append failure.
The nvlist_free() function removes element of the given name from the nvlist (besides of its
type) and frees all resources associated with it. If element of the given name does not
exist, the program will be aborted. The nvlist must not be in error state.
The nvlist_free_type() function removes element of the given name and the given type from
the nvlist and frees all resources associated with it. If element of the given name and the
given type does not exist, the program will be aborted. The nvlist must not be in error
state.
The nvlist_free_null(), nvlist_free_bool(), nvlist_free_number(), nvlist_free_string(),
nvlist_free_nvlist(), nvlist_free_descriptor(), nvlist_free_binary(),
nvlist_free_bool_array(), nvlist_free_number_array(), nvlist_free_string_array(),
nvlist_free_nvlist_array(), nvlist_free_descriptor_array() functions remove element of the
given name and the given type determined by the function name from the nvlist and free all
resources associated with it. If element of the given name and the given type does not
exist, the program will be aborted. The nvlist must not be in error state.
NOTES
The nvlist_pack() and nvlist_unpack() functions handle the byte-order conversions, so the
binary buffer can be packed/unpacked by the hosts with the different endianness.
EXAMPLES
The following example demonstrates how to prepare an nvlist and send it over unix(4) domain
socket.
nvlist_t *nvl;
int fd;
fd = open("/tmp/foo", O_RDONLY);
if (fd < 0)
err(1, "open(\"/tmp/foo\") failed");
nvl = nvlist_create(0);
/*
* There is no need to check if nvlist_create() succeeded,
* as the nvlist_add_<type>() functions can cope.
* If it failed, nvlist_send() will fail.
*/
nvlist_add_string(nvl, "filename", "/tmp/foo");
nvlist_add_number(nvl, "flags", O_RDONLY);
/*
* We just want to send the descriptor, so we can give it
* for the nvlist to consume (that's why we use nvlist_move
* not nvlist_add).
*/
nvlist_move_descriptor(nvl, "fd", fd);
if (nvlist_send(sock, nvl) < 0) {
nvlist_destroy(nvl);
err(1, "nvlist_send() failed");
}
nvlist_destroy(nvl);
Receiving nvlist and getting data:
nvlist_t *nvl;
const char *command;
char *filename;
int fd;
nvl = nvlist_recv(sock, 0);
if (nvl == NULL)
err(1, "nvlist_recv() failed");
/* For command we take pointer to nvlist's buffer. */
command = nvlist_get_string(nvl, "command");
/*
* For filename we remove it from the nvlist and take
* ownership of the buffer.
*/
filename = nvlist_take_string(nvl, "filename");
/* The same for the descriptor. */
fd = nvlist_take_descriptor(nvl, "fd");
printf("command=%s filename=%s fd=%d0, command, filename, fd);
nvlist_destroy(nvl);
free(filename);
close(fd);
/* command was freed by nvlist_destroy() */
Iterating over nvlist:
nvlist_t *nvl;
const char *name;
void *cookie;
int type;
nvl = nvlist_recv(sock, 0);
if (nvl == NULL)
err(1, "nvlist_recv() failed");
cookie = NULL;
while ((name = nvlist_next(nvl, &type, &cookie)) != NULL) {
printf("%s=", name);
switch (type) {
case NV_TYPE_NUMBER:
printf("%ju", (uintmax_t)nvlist_get_number(nvl, name));
break;
case NV_TYPE_STRING:
printf("%s", nvlist_get_string(nvl, name));
break;
default:
printf("N/A");
break;
}
printf("\n");
}
Iterating over every nested nvlist:
nvlist_t *nvl;
const char *name;
void *cookie;
int type;
nvl = nvlist_recv(sock, 0);
if (nvl == NULL)
err(1, "nvlist_recv() failed");
cookie = NULL;
do {
while ((name = nvlist_next(nvl, &type, &cookie)) != NULL) {
if (type == NV_TYPE_NVLIST) {
nvl = nvlist_get_nvlist(nvl, name);
cookie = NULL;
}
}
} while ((nvl = nvlist_get_parent(nvl, &cookie)) != NULL);
Iterating over every nested nvlist and every nvlist element:
nvlist_t *nvl;
const nvlist_t * const *array;
const char *name;
void *cookie;
int type;
nvl = nvlist_recv(sock, 0);
if (nvl == null)
err(1, "nvlist_recv() failed");
cookie = null;
do {
while ((name = nvlist_next(nvl, &type, &cookie)) != NULL) {
if (type == NV_TYPE_NVLIST) {
nvl = nvlist_get_nvlist(nvl, name);
cookie = NULL;
} else if (type == NV_TYPE_NVLIST_ARRAY) {
nvl = nvlist_get_nvlist_array(nvl, name, NULL)[0];
cookie = NULL;
}
}
} while ((nvl = nvlist_get_pararr(nvl, &cookie)) != NULL);
Or alternatively:
nvlist_t *nvl, *tmp;
const nvlist_t * const *array;
const char *name;
void *cookie;
int type;
nvl = nvlist_recv(sock, 0);
if (nvl == null)
err(1, "nvlist_recv() failed");
cooke = NULL;
tmp = nvl;
do {
do {
nvl = tmp;
while ((name = nvlist_next(nvl, &type, &cookie)) != NULL) {
if (type == NV_TYPE_NVLIST) {
nvl = nvlist_get_nvlist(nvl,
name);
cookie = NULL;
} else if (type == NV_TYPE_NVLIST_ARRAY) {
nvl = nvlist_get_nvlist_array(nvl, name,
NULL)[0];
cookie = NULL;
}
}
cookie = NULL;
} while ((tmp = nvlist_get_array_next(nvl)) != NULL);
} while ((tmp = nvlist_get_parent(nvl, &cookie)) != NULL);
SEE ALSO
close(2), dup(2), open(2), err(3), free(3), printf(3), unix(4)
HISTORY
The libnv library appeared in FreeBSD 11.0.
AUTHORS
The libnv library was implemented by Pawel Jakub Dawidek <pawel@dawidek.net> under
sponsorship from the FreeBSD Foundation.