The function updates 
err with the result of the operation if necessary:
- If the format of the sequence is not valid, the function sets 
failbit.
- Otherwise, it is unspecified, although some implementations set 
err to 
eofbit if the function exhausts the sequence of characters (i.e., it reaches 
end, both in case of success and failure), or to 
goodbit otherwise.
The function updates 
err with the result of the operation if necessary:
- If the format of the sequence is not valid, the function sets 
failbit.
- If the function exhausts the sequence of characters (i.e., it reaches 
end) during its operations, it sets 
eofbit (both 
failbit and 
eofbit may be set by a single operation).
- Otherwise, it is unspecified, although some implementations set 
err to 
goodbit.