Date: Mon, 3 Dec 2012 22:43:38 +0200 (EET) From: long@rule.lv To: "Frank Reppin" <frank@undermydesk.org> Cc: freebsd-questions@freebsd.org Subject: Re: bash pipe redirection gets stuck Message-ID: <62300.217.24.65.29.1354567418.squirrel@mail.rule.lv> In-Reply-To: <50BCE7A9.7060107@undermydesk.org> References: <23353.144.36.114.84.1354545315.squirrel@mail.rule.lv> <50BCE7A9.7060107@undermydesk.org>
next in thread | previous in thread | raw e-mail | index | archive | help
> On 03.12.12 15:35, long@rule.lv wrote: > [...] >> I stumbled upon a problem where multiple pipe redirection occasionally >> get >> stuck when trying to get sha256 sum of a stream. >> >> You can try to reproduce the problem if you have /usr/ports/shells/bash >> installed (output redirection used in this command is possible only in >> bash). >> Create temporary test file with command: "dd if=/dev/urandom >> of=/tmp/file1 >> bs=1k count=10" >> And the command I'm using is: >> /usr/local/bin/bash -c 'cat /tmp/file1 | tee >(/sbin/sha256 > >> /tmp/file1.sha256) > /tmp/file1.copy' ; echo $status >> >> Command gets stuck about once in 20 executions. >> top output when command gets stuck (irrelevant processes removed): >> PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU >> COMMAND >> 84073 HappyUser 1 52 0 17612K 2268K wait 0 0:00 0.00% >> bash >> 84154 HappyUser 1 52 0 10084K 844K fifoow 1 0:00 0.00% tee >> >> And more strangely, I can reproduce this problem on 9.0-RELEASE and >> 7.4-RELEASE-p6, but couldn't reproduce on 8.2-RELEASE-p4. > It maybe couldn't gather more randomness from /dev/random? > The random(4) manpage suggests that there's (theoretically) > indeed a chance that it blocks - see the section about > 'kern.random.sys.seeded'. > So in fact - when you think the command gets stuck - it's > probably not bash related at all. > > cheers, > Frank Reppin > > -- > 43rd Law of Computing: > Anything that can go wr > fortune: Segmentation violation -- Core dumped > > Thanks for your answer, but randomly generated file is created fine (it is only for illustrative purpose). As far as I understand, thing that blocks is tee inside bash command or pipeline. Thanks and best regards, Normunds
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?62300.217.24.65.29.1354567418.squirrel>