3 iounit \- return size of atomic I/O unit for file descriptor
12 Reads and writes of files are transmitted using the 9P protocol (see
14 and in general, operations involving large amounts of data must be
15 broken into smaller pieces by the operating system.
16 The `I/O unit' associated with each file descriptor records the maximum
17 size, in bytes, that may be read or written without breaking up the transfer.
23 interface to discover the I/O unit size for the file descriptor
25 and returns its value.
26 Certain file descriptors, particularly those associated with devices, may
27 have no specific I/O unit, in which case
37 Returns zero if any error occurs or if the I/O unit size of the fd is unspecified or unknown.