From kragen@dnaco.net Fri Sep 25 00:25:22 1998 Date: Fri, 25 Sep 1998 00:25:20 -0400 (EDT) From: Kragen X-Sender: kragen@pike To: Richard S Harlan cc: jweirich@one.net, talk@clug.org Subject: Re: CLUG Talk Puzzler In-Reply-To: <19980925.003543.11806.1.rick.harlan@juno.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Keywords: X-UID: 2150 Status: O X-Status: On Thu, 24 Sep 1998, Richard S Harlan wrote: > On Thu, 24 Sep 1998 10:52:57 -0400 (EDT) Kragen > writes: > >They have the disadvantage that you can't build commands in which the > >non-directed dataflow graph has cycles. For example, I can't run a > >command that produces two outputs, each of which gets processed by an > >instance of another command before being compared by a third command. > >I need mkfifo for that. > > Now, if you could build a directed graph with cycles, Jim could add it to > his collection of infinite loops (something like "cat 1>0&", maybe?). mkfifo x cat < x | (echo a; cat) > x does indeed go into an infinite loop. If you take out the echo a, it deadlocks instead, which is really quite similar. In this case, the dataflow graph itself has cycles. There are other cases, more useful, in which the dataflow graph itself, being a directed graph, has no cycles, but the non-directed version of the dataflow graph does. Like a -> b, a -> c, b -> d, c -> d, for example. cat 1>0 doesn't work, because (1) you meant >&0, not >0, and (2) if you write data to fd 0, it is unlikely that reading fd 0 will then let you read the data back. > [2] It's bad enough having to run PC software under emulation. I'm > beginning to think that it's worse when they actually port to Unix; I > don't think they bother to fix the bugs that no one notices in Windows, > since everything else is so buggy. There's another thing -- the app developers worked around Windows's bugs, but they didn't work around the emulator's bugs. Kragen -- Kragen Sitaker The sages do not believe that making no mistakes is a blessing. They believe, rather, that the great virtue of man lies in his ability to correct his mistakes and continually make a new man of himself. -- Wang Yang-Ming