On Wed, Apr 20, 2005 at 05:35:28PM +0200, Marc Olzheim wrote:

This specific issue is not clear-cut; the best thing to do lies somewhere within the range of these scenarios:

"If a write() requests that more bytes be written than there is room for (for example, [XSI] [Option Start] the process' file size limit or [Option End] the physical end of a medium), only as many bytes as there is room for shall be written. For example, suppose there is space for 20 bytes more in a file before reaching a limit. A write of 512 bytes will return 20. The next write of a non-zero number of bytes would give a failure return (except as noted below)."

"When attempting to write to a file descriptor (other than a pipe or FIFO) that supports non-blocking writes and cannot accept the data immediately:

* If the O_NONBLOCK flag is clear, write() shall block the calling thread until the data can be accepted.

* If the O_NONBLOCK flag is set, write() shall not block the thread. If some data can be written without blocking the thread, write() shall write what it can and return the number of bytes written. Otherwise, it shall return -1 and set errno to [EAGAIN]."

"[ENOBUFS] Insufficient resources were available in the system to perform the operation."

I think the first is more useful behavior than the last. Supporting it should be exactly the same as supporting what happens if the actual filesystem fills up. In this case, the filesystem is being requested to write more "than there is room for."