Testing I/O success

[John F. Haugh II]

In article <8038 at boring.cwi.nl> siebren at cwi.nl (Siebren van der Zee) writes:
>In article <8019 at boring.cwi.nl>, I, siebren at cwi.nl (Siebren van der Zee) wrote:
>> You *CANNOT* detect disk-full always on unix, since I/O is lazy.
>
>As several people pointed out to me, I was wrong. Even though the actual
>write may take place by the time that the program has exited, the disk-
>blocks are allocated immediately. Only when the write fails, you won't
>be notified, unless you call fsync(int fd).
>This is true for 4.3 BSD, SunOS 3.5, Ultrix 2.2; every unix I could check.

Part wrong still.  The disk blocks aren't allocated until stdio has flushed
it's buffers and called write(), etc.  A common problem is programs which
never fclose() their buffered files and rely on exit() to do so.  ALWAYS
flush after writes which must check for I/O success.
-- 
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