Re: |& in bash?

[Steven W. Orr]

On 1/21/2013 1:20 PM, John Caruso wrote:
> In article <mailman.17846.1358543463.855.bug-bash@gnu.org>, Dan Douglas wrote:
> > It isn't very common to dump multiple streams into one pipe.
>
> echo "n't very"  >/dev/null 2>&1
>
> > I suggest avoiding |&.
>
> Personally I wouldn't use it in scripts, since I try to stick as close
> to plain vanilla Bourne shell as possible (though that's not as much of
> a consideration these days as it used to be).  But for interactive use
> it's one of the greatest shell time- and effort-savers I know of, and
> I'm very happy to hear it's made its way into bash.  I wouldn't suggest
> avoiding it unless you like carpal tunnel.
>
> - John

Just an old observation. I much prefer use of |& for the simple reason that it 
provides greater consistency.

foo > out 2>&1
The above uses the file out to capture stdout and stderr. The order of 
evaluation is important and if you were to say
foo 2>&1 > out
it wouldn't work because you would be redirecting stderr to stdout before 
stdout was redirected to a file.

By that logic,

foo 2>&1 | bar

should not work, but it does. It takes stderr and dups it to stdout, and 
*then* takes stdout and send it to a pipe.

The proper way that it should have been done (if I was Emperor of the 
Universe) would have been

foo | 2>&1 bar

I accept that the | delimits what happens in the two different processes, so 
this is not material subject to a jihad. Just an observation from a language 
lawyer.

--
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steveo at syslang.net