From: wkt@tuhs.org (Warren Toomey)
Subject: [TUHS] Excise process from a pipe
Date: Thu, 10 Jul 2014 18:43:57 +1000 [thread overview]
Message-ID: <20140710084357.GA27008@www.oztivo.net> (raw)
In-Reply-To: <CA+Z8kA7v=Uy3xRVhgYhxqwNv4kxS31uO55GK695nfdj8pWBjzA@mail.gmail.com>
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> On Thu, Jul 10, 2014 at 2:52 PM, Warren Toomey <[1]wkt at tuhs.org> wrote:
> Â Â Â Â close fd 0 and fd 1
> Â Â Â Â dup() read end of pipe 1 to be stdin (fd 0)
> Â Â Â Â dup() write end of pipe 2 to be stdout (fd 1)
> Â Â Â Â exec("/bin/cat")
On Thu, Jul 10, 2014 at 03:06:11PM +1000, Christopher Vance wrote:
> Hi, Warren.
> That still leaves a process, even if it is a relatively lean one.
Hi Chris! Very true.
> Besides your fd 0 is presumably already the read end of the input pipe,
> and fd 1 is already the write end of the output pipe. You could
> probably reduce the whole thing to the last line.
Of course. If the shell set up the pipeline then we only have to exec("cat")
and leave /bin/cat shuffling the data from one pipe-end to the other.
As there are two distinct pipes, each with their own buffers, I can't see
a way of coalescing them into a single pipe without, as Chris suggests,
some kernelly goodness. Indeed, ugliness and complexity kernel-wise!
Cheers, Warren
next prev parent reply other threads:[~2014-07-10 8:43 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-10 2:49 [TUHS] Subject:unpipeIt'seasy for a process to insert a new process intoapipelineeither upstream or down unpipe Doug McIlroy
2014-07-10 4:52 ` [TUHS] Excise process from a pipe Warren Toomey
2014-07-10 5:00 ` Dave Horsfall
2014-07-10 5:06 ` Christopher Vance
2014-07-10 8:43 ` Warren Toomey [this message]
2014-07-10 12:03 ` Doug McIlroy
2014-07-10 12:04 ` Doug McIlroy
2014-07-10 14:45 ` Larry McVoy
2014-07-10 15:10 Noel Chiappa
2014-07-10 15:11 ` Larry McVoy
2014-07-10 16:06 Noel Chiappa
2014-07-10 16:04 ` Larry McVoy
2014-07-10 16:12 Noel Chiappa
2014-07-14 14:13 Doug McIlroy
2014-07-14 15:12 Noel Chiappa
2014-07-16 21:31 Noel Chiappa
2014-07-17 15:42 Noel Chiappa
2014-07-18 15:33 Noel Chiappa
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