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Re: Here document / redirection / background process weirdness


From: Martin Jackson
Subject: Re: Here document / redirection / background process weirdness
Date: Wed, 13 Mar 2013 14:04:52 +0100

I didn't see any acknowledgement of this bug report, did I fill in enough
info?

Thanks & regards,

Martin Jackson


On Tue, Mar 5, 2013 at 1:52 PM, Martin Jackson
<address@hidden>wrote:

> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-unknown-linux-gnu'
> -DCONF_VENDOR='unknown'
> -DLOCALEDIR='/home/mjackson/src/bash-4.2/_install/share/locale'
> -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib
> -g -O2
> uname output: Linux stagecoach 3.5.0-25-generic #39-Ubuntu SMP Mon Feb 25
> 18:26:58 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
> Machine Type: x86_64-unknown-linux-gnu
>
> Bash Version: 4.2
> Patch Level: 0
> Release Status: release
>
> Description:
> When executing a here document in bash, with the here document piped to
> another instance of bash, where the here document contains "echo <&- &;
> wait", the here document gets executed twice. I have seen this on Ubuntu
> both with the current 4.2.37 from ubuntu and the latest bash tarball
> (details above)
>
> Repeat-By:
>     #!/home/mjackson/src/bash-4.2/_install/bin/bash
>
>     /home/mjackson/src/bash-4.2/_install/bin/bash <<EOF
>     declare -i a=0
>     echo BASHPID is \$BASHPID
>     true </dev/null & wait # NOP
>     let a++
>     echo a is \$a, BASHPID is \$BASHPID
>     EOF
>
>     Prints:
>     BASHPID is 30866
>     a is 1, BASHPID is 30866
>     a is 2, BASHPID is 30866
>
> Fix:
>     Adding a manual 'exit' statement at the end of the here document seems
> to be a workaround:
>
>     #!/home/mjackson/src/bash-4.2/_install/bin/bash
>
>     /home/mjackson/src/bash-4.2/_install/bin/bash <<EOF
>     declare -i a=0
>     echo BASHPID is \$BASHPID
>     true </dev/null & wait # NOP
>     let a++
>     echo a is \$a, BASHPID is \$BASHPID
>     exit
>     EOF
>
>     Prints:
>     BASHPID is 30895
>     a is 1, BASHPID is 30895
>
>


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