bash pipe redirection gets stuck
long at rule.lv
long at rule.lv
Mon Dec 3 14:45:01 UTC 2012
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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