From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 53198 invoked by alias); 26 Feb 2016 13:50:46 -0000 Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Received: (qmail 53185 invoked by uid 89); 26 Feb 2016 13:50:45 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=1.0 required=5.0 tests=AWL,BAYES_50,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS,TBC autolearn=no version=3.3.2 spammy=txt, Enterprise, edition, hangs X-HELO: mail-wm0-f48.google.com Received: from mail-wm0-f48.google.com (HELO mail-wm0-f48.google.com) (74.125.82.48) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Fri, 26 Feb 2016 13:50:44 +0000 Received: by mail-wm0-f48.google.com with SMTP id g62so73714770wme.1 for ; Fri, 26 Feb 2016 05:50:44 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding; bh=yfjJP7YhevdZlBGe3lCxxfcvd3g9onczno/0AKMPckA=; b=V+a7igFzaiDQPw36nV3QitdQhHKL4y2ZYplWUBJEnpKbuiGthE/VY+nvQuNDlZ8j5L pQ7bCSKEJqCUKTDW6DOl3I2TWv2XsqYPkjrLYP+ODo1udmo3/qlcq/oqiP65NUEyrhtV RQYnANfWPnwqevT5YFeJQ4m5VCZtP87EdkgRpsSJkSRXUgJxrmvnd3/ZB5j5fQR+YnzK Eyo8g6h73ji2zIDGMod5F0fbh14WSFqj+M+KFisnHzylJvIHJ4Aw9HjYBvY3KyX1b9dm wilxLW9ZF0Xvz5IUzCjLNTrenfeVRsf4FcHNjnkYa5TKriv9BBWBKwrCww/7ZCBurLzF r6Lw== X-Gm-Message-State: AD7BkJIXaqtyLaTh0skQLBHcXAeH9IDUrcNWNCmXjtCjYJmGEfkgcMkA8BAbgGPl0zPsuw== X-Received: by 10.194.115.196 with SMTP id jq4mr1801701wjb.101.1456494641719; Fri, 26 Feb 2016 05:50:41 -0800 (PST) Received: from [172.21.188.188] ([62.154.173.198]) by smtp.googlemail.com with ESMTPSA id g126sm2962834wmf.16.2016.02.26.05.50.40 for (version=TLSv1/SSLv3 cipher=OTHER); Fri, 26 Feb 2016 05:50:40 -0800 (PST) Subject: Re: echo -n or sleep 0 needed to unblock Bourne shell script To: cygwin@cygwin.com References: From: Marco Atzeri Message-ID: <56D0582D.1090608@gmail.com> Date: Fri, 26 Feb 2016 13:50:00 -0000 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2016-02/txt/msg00404.txt.bz2 On 26/02/2016 14:04, Matthijs Nescio wrote: > Hi, > > I have the strangest problem. I am running some complicated advanced Bourne shell scripting. These scripts work fine under Ubuntu 14.04 LTS. However, in Cygwin I have to add some strange commands with no obvious effect; without these the scripts just hang. I can not disclose the scripts completely because they are company property. I realise that this does not comply to the rules of smart questions, but if anybody else has this problem the Cygwinners need to know about it. I do not exactly know when these problems started. I reinstalled Cygwin twice, several weeks ago and yesterday evening. > > I have had this problem with several complicated, lengthy scripts. Debugging using echo debug statements is hard because the echo makes the problem go away. When I discovered similar problems in multiple scripts, I reinstalled Cygwin, but the problem persists. Also rebooting my Windows 7 Enterprise edition machine does not solve the problem. I have had some experienced colleagues to look at this and they were as flabbergasted as I was. > > Examples: > > TTP_FILE_DR_KML=`echo $TTP_FILE.dr.kml | sed -s 's#\.txt\.#\.#g'` > #echo -n> /dev/null > sleep 0 > if [ "`convert_needed "$TTP_FILE_DR_KML"`" = "convert" ] > then > > In the examples above and below, either the sleep or the echo has to be commented in, otherwise the script just hangs. In the example below the doit function needs the echo or sleep, otherwise it does not return. > > doit() > { > # 8< code removed > #echo -n > sleep 0 > } > > In > order to investigate this problem the Cywinners will need more information. Feel free to ask, but it may not be legal for me to share. > > Questions: > * Was a similar issue ever reported? I have looked, but did not find anything. > * Is there a solution? > > Thank you, kind regards, Matthijs. I suspect you hit a corner case of resource race. May be as the time for execution is very short : $ time echo -n > /dev/null 0 real 0m0.000s user 0m0.000s sys 0m0.000s $ time sleep 0 real 0m0.070s user 0m0.015s sys 0m0.062s As both the two commands are just supposed to waste minimal time, what was the original need of both of them ? -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple