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Re: Shell (bash, (pd)ksh, zsh, /not/ ash) + exec + here-doc +redirect == trouble!
- From: ericblake at comcast dot net (Eric Blake)
- To: cygwin at cygwin dot com
- Date: Wed, 25 Jan 2006 15:48:37 +0000
- Subject: Re: Shell (bash, (pd)ksh, zsh, /not/ ash) + exec + here-doc +redirect == trouble!
> You might want to quote <<'EOSH', but that's not the cause of your
> problem. Here's a funny thing:
> exec 5<&0 /bin/bash <<'EOSH'
> echo "First exec: Done."
> exec 0<&5
> echo "Second exec: Done."
> exit 0
> works for me. Don't ask me why, though. Perhaps Eric will chime in.
Define "works for me".
First exec: Done.
echo "Second exec: Done."
Here, the cat uses fd 0 (which is still set to the pipe from the
here-doc), and consumes it by echoing the remainder of
the here-doc to stdout, so that when /bin/bash goes
to read the next line, fd 0 is at EOF, and you never execute
the "exec 0<&5" line in the shell. Thus, the process never
tries to duplicate fd 5 back to fd 0, and your example no longer
hangs waiting for input from the terminal. But it doesn't do what
was originally intended (that is, allow /bin/bash to execute
the remainder of the here-doc).
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