From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 14660 invoked from network); 4 Oct 1999 18:44:06 -0000 Received: from sunsite.auc.dk (130.225.51.30) by ns1.primenet.com.au with SMTP; 4 Oct 1999 18:44:06 -0000 Received: (qmail 13820 invoked by alias); 4 Oct 1999 18:42:44 -0000 Mailing-List: contact zsh-users-help@sunsite.auc.dk; run by ezmlm Precedence: bulk X-No-Archive: yes X-Seq: 2658 Received: (qmail 13813 invoked from network); 4 Oct 1999 18:42:43 -0000 From: "Bart Schaefer" Message-Id: <991004184232.ZM3484@candle.brasslantern.com> Date: Mon, 4 Oct 1999 18:42:32 +0000 In-Reply-To: <199910041610.MAA20728@betelgeuse.ccs.neu.edu> Comments: In reply to Jay Sekora "Re: coproc tutorial (Re: questions)" (Oct 4, 12:10pm) References: <199910041610.MAA20728@betelgeuse.ccs.neu.edu> X-Mailer: Z-Mail Lite (5.0.0 30July97) To: zsh-users@sunsite.auc.dk Subject: Re: coproc tutorial (Re: questions) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii On Oct 4, 12:10pm, Jay Sekora wrote: > Subject: Re: coproc tutorial (Re: questions) > It seems a little bit non-orthoganal that you can only have one > coprocess. It's not the case that there can be only one coprocess. The restriction is that there can be only one pair of file descriptors referred to by the special "p" name, and closing them frequently has the effect of stopping the coprocess; but if you've copied those descriptors elsewhere you can still use the copies to communicate with the process. E.g. coproc tr a-z A-Z exec 5>&p ;: descriptor 5 is now the input of tr exec 6<&p ;: descriptor 6 is now the output of tr coproc sed s/DOG/CAT/ 5>&- exec 7>&p ;: descriptor 7 is now the input of sed exec 8<&p ;: descriptor 8 is now the output of sed coproc exit ;: close p cat <&6 >&7 5>&- 7>&- & : tr is now connected to sed exec 6<&- 7>&- ;: close shell copies of descriptors echo dog >&5 ;: send tr some input exec 5>&- ;: close 5 so tr will exit cat <&8 ;: should print CAT There are some oddities here ... first, note how I had to explicitly close descriptor 5 in the second coproc, and 5 and 7 in the backgrounded "cat". That's because they don't have the close-on-exec flag set; if I don't close them, "tr" and "sed" never see end-of-file. I'm not sure whether that is correct behavior or not. Second, this doesn't actually work in 3.0.6, because zsh "leaks" copies of descriptors 5 and 7 as descriptors 13 and 14 ("strace" is your friend), so even after all my careful descriptor-closing I still can't get "tr" to see EOF. It works in 3.1.6, so I may have a look at fixing it in 3.0.