On 1/5/16 11:47 AM, c...@cs.toronto.edu wrote:
> Bash Version: 4.3
> Patch Level: 11
> Release Status: release
>
> Description:
>
> If Bash writes to stdout with the built in echo and gets a SIGPIPE,
> it can incorrectly buffer and then repeat this would-have-been output
> in at least $(...) things invoked in a cleanup function and in fact
> in some other contexts as well. To see this in action, create the
> following script as /tmp/repro:
>
> #!/bin/bash
> function cleanup() {
> r1=$(/bin/echo one)
> r2=$(/bin/echo two)
> echo $r1 '!' $r2 1>&2
> #echo $r1 '!' $r2 >>/tmp/logout
> }
> trap cleanup EXIT
> sleep 1
> echo final
>
> Run it as '/tmp/repro | false'. The output produced is the clearly
> incorrect:
> $ /tmp/repro | false
> final
> one final ! two final
Thanks for the report. This appears to be easily reproducible on Linux.
Adding a call to fpurge() to discard buffered output on stdout before
dup2() replaces file descriptor 1 in the child process fixes it.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU c...@case.edu http://cnswww.cns.cwru.edu/~chet/
