flush() before use...

Elric of Grans · 07-12-2005, 05:47 PM

G'Day,

I am working on a Linux device driver, and have already implimented the basic open(), read(), write() and close() function. The next thing I need to add is a flush() operation, as there are several things that need to be reinitialised between tasks. I think I know what to do on the kernel side of things, but I actually do not know what the flush command is! There does not seem to be an actual `int flush(int fd)' function (at least, there is no man page for it on my system), so I guess the function is named something else.

Simple question, really: what is the C function that falls the flush() operation from a device driver?

exvor · 07-12-2005, 07:54 PM

here is an excerpt from the gnu c programming tutorial for fflush im sure flush is similar tho.

Quote:

Having stdin and stdout be line-buffered is convenient, because most meaningful chunks of data you write to them are terminated with a newline character. In order to ensure that the data you read from or write to a fully-buffered stream shows up right away, use the fflush function. In the jargon, this is called flushing the stream. Flushing moves the characters from the buffer to the file, if they haven't already been moved. After the move, other functions can then work on the characters.1

To use fflush, simply pass the function the stream you want to flush. The fflush function returns 0 if successful, or the value EOF (which is a macro defined in the GNU C Library) if there was a write error.