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[129.22.8.211]) by smtp.gmail.com with ESMTPSA id a30-20020a05620a439e00b0078d73533196sm8431989qkp.76.2024.04.17.07.20.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Apr 2024 07:20:35 -0700 (PDT) Message-ID: Date: Wed, 17 Apr 2024 10:20:34 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chet.ramey@case.edu, Martin D Kealey , Zachary Santer , bug-bash , libc-alpha@sourceware.org Subject: Re: Examples of concurrent coproc usage? Content-Language: en-US To: Carl Edquist References: <9831afe6-958a-fbd3-9434-05dd0c9b602a@draigBrady.com> <317fe0e2-8cf9-d4ac-ed56-e6ebcc2baa55@cs.wisc.edu> <8c490a55-598a-adf6-67c2-eb2a6099620a@cs.wisc.edu> <88a67f36-2a56-a838-f763-f55b3073bb50@lando.namek.net> <2791ad90-a871-474d-89dd-bc6b20cdd1f2@case.edu> <32bd9e76-24bc-4206-aa8a-8bcc817228b1@case.edu> From: Chet Ramey Autocrypt: addr=chet.ramey@case.edu; keydata= xsDiBEEOsGwRBACFa0A1oa71HSZLWxAx0svXzhOZNQZOzqHmSuGOG92jIpQpr8DpvgRh40Yp AwdcXb8QG1J5yGAKeevNE1zCFaA725vGSdHUyypHouV0xoWwukYO6qlyyX+2BZU+okBUqoWQ koWxiYaCSfzB2Ln7pmdys1fJhcgBKf3VjWCjd2XJTwCgoFJOwyBFJdugjfwjSoRSwDOIMf0D /iQKqlWhIO1LGpMrGX0il0/x4zj0NAcSwAk7LaPZbN4UPjn5pqGEHBlf1+xDDQCkAoZ/VqES GZragl4VqJfxBr29Ag0UDvNbUbXoxQsARdero1M8GiAIRc50hj7HXFoERwenbNDJL86GPLAQ OTGOCa4W2o29nFfFjQrsrrYHzVtyA/9oyKvTeEMJ7NA3VJdWcmn7gOu0FxEmSNhSoV1T4vP2 1Wf7f5niCCRKQLNyUy0wEApQi4tSysdz+AbgAc0b/bHYVzIf2uO2lIEZQNNt+3g2bmXgloWm W5fsm/di50Gm1l1Na63d3RZ00SeFQos6WEwLUHEB0yp6KXluXLLIZitEJM0gQ2hldCBSYW1l eSA8Y2hldC5yYW1leUBjYXNlLmVkdT7CYQQTEQIAIQIbAwYLCQgHAwIDFQIDAxYCAQIeAQIX gAUCRX3FIgIZAQAKCRC7WGnwZOp0q069AKCNDRn+zzN/AHbaynls/Lvq1kH/RQCgkLvF8bDs maUHSxSIPqzlGuKWDxbOwE0EQQ6wbxAEAJCukwDigRDPhAuI+lf+6P64lWanIFOXIndqhvU1 3cDbQ/Wt5LwPzm2QTvd7F+fcHOgZ8KOFScbDpjJaRqwIybMTcIN0B2pBLX/C10W1aY+cUrXZ gXUGVISEMmpaP9v02auToo7XXVEHC+XLO9IU7/xaU98FL69l6/K4xeNSBRM/AAMHA/wNAmRB pcyK0+VggZ5esQaIP/LyolAm2qwcmrd3dZi+g24s7yjV0EUwvRP7xHRDQFgkAo6++QbuecU/ J90lxrVnQwucZmfz9zgWDkT/MpfB/CNRSKLFjhYq2yHmHWT6vEjw9Ry/hF6Pc0oh1a62USdf aKAiim0nVxxQmPmiRvtCmcJJBBgRAgAJBQJBDrBvAhsMAAoJELtYafBk6nSr43AAn2ZZFQg8 Gs/zUzvXMt7evaFqVTzcAJ0cHtKpP1i/4H4R9+OsYeQdxxWxTQ== In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Mirapoint-Received-SPF: 209.85.222.198 mail-qk1-f198.google.com chet.ramey@case.edu 5 none X-Mirapoint-IP-Reputation: reputation=Good-1, source=Queried, refid=tid=0001.0A742F91.661FD60D.000E, actions=spf tag X-Mirapoint-IP-Reputation: reputation=good-1, source=Fixed, refid=n/a, actions=tag X-Junkmail-Status: score=8/90, host=mpv-out-ksl-1.case.edu X-Junkmail-PrAS-Raw: score=8/90, refid=2.7.2:2023.6.26.145126:17:8.707, ip=, rules=__YOUTUBE_RCVD, DKIM_SIGNATURE, __X_GOOGLE_DKIM_SIGNATURE, __X_GM_MESSAGE_STATE, __X_GOOGLE_SMTP_SOURCE, __HAS_MSGID, __SANE_MSGID, __MSGID_HEX_844412, DATE_TZ_NA, __MIME_VERSION, __USER_AGENT, __MOZILLA_USER_AGENT, __HAS_REPLYTO, __HAS_CC_HDR, __MULTIPLE_RCPTS_CC_X2, __CC_NAME, __CC_NAME_DIFF_FROM_ACC, __SUBJ_REPLY, __BOUNCE_CHALLENGE_SUBJ, __BOUNCE_NDR_SUBJ_EXEMPT, __TO_MALFORMED_2, __TO_NAME, __TO_NAME_DIFF_FROM_ACC, __HAS_REFERENCES, __REFERENCES, __HAS_FROM, FROM_EDU_TLD, __IN_REP_TO, __CT, __CT_TEXT_PLAIN, __MIME_BOUND_CHARSET, __CTE, CTE_8BIT, __REPLYTO_SAMEAS_FROM_ADDY, __REPLYTO_SAMEAS_FROM_ACC, __RCPT_DOMAIN_NOT_TO, __REPLYTO_SAMEAS_FROM_DOMAIN, __DKIM_ALIGNS_1, __DKIM_ALIGNS_2, __FUR_HEADER, __ANY_URI, __URI_MAILTO, __URI_WITH_PATH, __URI_ENDS_IN_SLASH, __URI_NO_WWW, __CP_URI_IN_BODY, __FRAUD_URGENCY, __SUBJ_ALPHA_NEGATE, __URI_IN_BODY, [TRUNCATED], so=2010-03-03 19:42:08, dmn=2016-08-03-0138 X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: chet.ramey@case.edu Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org On 4/15/24 1:01 PM, Carl Edquist wrote: > On Sat, 13 Apr 2024, Chet Ramey wrote: > >> The original intent was to allow the shell to drive a long-running >> process that ran more-or-less in parallel with it. Look at >> examples/scripts/bcalc for an example of that kind of use. > > Thanks for mentioning this example.  As you understand, this model use case > does not require closing the coproc fds when finished, because they will be > closed implicitly when the shell exits.  (As bcalc itself admits.) > > And if the coproc is left open for the lifetime of the shell, the alternate > behavior of deferring the coproc deallocation (until both coproc fds are > closed) would not require anything extra from the user. > > The bcalc example does close both coproc fds though - both at the end, and > whenever it resets.  And so in this example (which as you say, was the > original intent), the user is already explicitly closing both coproc fds > explicitly; so the alternate deferring behavior would not require anything > extra from the user here either. > > ... > > Yet another point brought to light by the bcalc example relates to the > coproc pid variable.  The reset() function first closes the coproc pipe > fds, then sleeps for a second to give the BC coproc some time to finish. > > An alternative might be to 'wait' for the coproc to finish (likely faster > than sleeping for a second). If the coproc has some problem and doesn't exit immediately, `wait' without options will hang. That's why I opted for the sleep/kill-as-insurance combo. (And before you ask why I didn't use `wait -n', I wrote bcalc in 30 minutes after someone asked me a question about doing floating point math with awk in a shell script, and it worked.) -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRU chet@case.edu http://tiswww.cwru.edu/~chet/