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Date:      Mon, 3 Dec 2012 16:35:15 +0200 (EET)
From:      long@rule.lv
To:        freebsd-questions@freebsd.org
Subject:   bash pipe redirection gets stuck
Message-ID:  <23353.144.36.114.84.1354545315.squirrel@mail.rule.lv>

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Dear all,
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.

Thanks for any pointers/explanations,
Normunds




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