The fsync() function takes a Perl file handle as its only argument, and
passes its fileno() to the C function fsync(). It returns I on
failure, or I on success.
The fsync_fd() function is used internally by fsync(); it takes a file
descriptor as its only argument.
The sync() function is identical to the C function sync().
This module does B export any methods by default, but fsync() is
made available as a method of the I and I