cpp/chrono/duration/from stream

Attempts to parse the input stream into the std, interpreted as the time of day since midnight, according to the format string.

Behaves as an, except that it has an unspecified effect on. After constructing and checking the sentry object, attempts to parse the input stream into  according to the format string. If the parse fails to decode a valid, is called and  is not modified.

If the format specifier is used and successfully parsed, the parsed value is assigned to  if  is not null. If the format specifier or a modified variant is used and successfully parsed, the parsed value is assigned to  if  is not null.

Return value
.