On 15/03/2015 19:39, Harald Becker wrote:
On most systems it is perfectly possible to have multiple readers on a pipe, when all readers and writers be so polite to use the same message size (<= PIPE_BUF). On most (but not all Unix systems) the kernel guaranties not only atomicity for write operations, but also for read operations (not in POSIX, AFAIK).
Second sentence of http://pubs.opengroup.org/onlinepubs/9699919799/functions/read.html : The behavior of multiple concurrent reads on the same pipe, FIFO, or terminal device is unspecified. What "most systems" do in practice is irrelevant. There is no guarantee at all on what a system will do when you have multiple readers on the same pipe; so it's a bad idea, and I don't see that there's any room for discussion here. If, say, Linux has documentation somewhere explaining what it does with multiple readers on a pipe, and committing to NOT changing that behaviour EVER, then it might be reasonable for Linux-specific software to rely on it. I'm not aware of such a piece of documentation though. -- Laurent _______________________________________________ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox
