The idea being that if milli and microseconds are present then you most likely want to retain them. The first three options are fast due to new specialized C code. R's internal UTC representation is written faithfully to encourage ISO standards, stymie timezone ambiguity and for speed.
This is new functionality as of Nov The file position indicator of the new stream is set to that belonging to fd, and the error and end-of-file indicators are cleared.
Cannot be the same as sep. Name change for consistency with 'fread' for which 'logicalAsInt' would not make sense. Details fwrite began as a community contribution with pull request by Otto Seiskari. Accordingly this can be slow. The file descriptor is not dup'ed, and will be closed when the stream created by fdopen is closed.
The fopenfdopen and freopen functions may also fail and set errno for any of the errors specified for the routine malloc 3. Old name for 'logical01'.
Therefore it is good practice and indeed sometimes necessary under Linux to put an fseek 3 or fgetpos 3 operation between write and read operations on such a stream. All other column types including Date, IDate and ITime which are independent of timezone are written as the "ISO" option using fast C code which is already consistent with write.