The callback receives the normalized name and value of each variable
in the config backend, and the data pointer passed to this function.
If the callback returns a non-zero value, the function stops iterating
and returns that value to the caller.
The pointers passed to the callback are only valid as long as the
iteration is ongoing.
Perform an operation on each config variable.
The callback receives the normalized name and value of each variable in the config backend, and the data pointer passed to this function. If the callback returns a non-zero value, the function stops iterating and returns that value to the caller.
The pointers passed to the callback are only valid as long as the iteration is ongoing.