Re: [kvm-unit-tests PATCH] scripts/arch-run: print stderr immediately

["Radim Krčmář" <rkrcmar@redhat.com>]

2016-11-03 13:38+0100, Paolo Bonzini:
> On 02/11/2016 22:05, Andrew Jones wrote:
>> On Wed, Nov 02, 2016 at 09:50:29PM +0100, Radim Krčmář wrote:
>>> Not doing so hid stderr output when the test was stuck and subsequently
>>> killed with ^C.
>>>
>>> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
>>> ---
>>>  scripts/arch-run.bash | 3 +--
>>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/scripts/arch-run.bash b/scripts/arch-run.bash
>>> index 8e75c6ed6e17..326f59484e2b 100644
>>> --- a/scripts/arch-run.bash
>>> +++ b/scripts/arch-run.bash
>>> @@ -30,12 +30,11 @@ run_qemu ()
>>>  
>>>  	# stdout to {stdout}, stderr to $errors
>>>  	exec {stdout}>&1
>>> -	errors=$("${@}" 2>&1 1>&${stdout})
>>> +	errors=$("${@}" 2> >(tee >(cat) >&2) 1>&${stdout})
> 
> What about:
> 
> # preserve stdout and stderr output, but save stderr to $errors
> exec {stdout}>&1 {stderr}>&2
> errors=$("$@" 2> >(tee /dev/fd/$stderr) > /dev/fd/$stdout)
> exec {stdout}>&- {stderr}>&-
> 
> (Tested in the shell but not in arch-run.bash).

Using files looks nicer, but is there a problem in the redirection?
I would rather use /dev/stderr or /dev/fd/2 directly if not.

i.e.
  exec {stdout}>&1
  errors=$("$@" 2> >(tee /dev/stderr) > /dev/fd/$stdout)
  exec {stdout}>&-