Manual Pages  — DNV

The dnvlist_get family of functions returns the value associated with the specified name. If an element of the specified name does not exist, the function returns the value provided in defval. Returned strings, nvlists, descriptors, binaries, or arrays must not be modified by the user. They still belong to the nvlist. If the nvlist is in an error state, attempts to use any of these functions will cause the program to abort.

The dnvlist_take family of functions returns the value associated with the specified name and removes the element from the nvlist. If an element of the supplied name does not exist, the value provided in defval is returned. When the value is a string, binary, or array value, the caller is responsible for freeing returned memory with free(3). When the value is an nvlist, the caller is responsible for destroying the returned nvlist with nvlist_destroy(). When the value is a descriptor, the caller is responsible for closing the returned descriptor with close(2).