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Re: foo | tee /dev/stderr | bar # << thanks!

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On Tue, Jul 07, 2020 at 07:41:51AM -0400, Greg Wooledge wrote:
> On Mon, Jul 06, 2020 at 09:45:59PM -0400, Dale R. Worley wrote:
> > bug-bash@trodman.com writes:
> > >     foo | tee >(cat >&2) | bar
> > 
> > I do wonder how portable >( ... ) is in practice, versus the portability
> > of /dev/stderr.  Maybe I worry about the former because I'm not
> > practiced in named-FIFO programming and so think of it as non-universal.
> 
> On Linux and BSD systems, >( ) will use a /dev/fd/ entry.  On most
> commercial Unix systems, where /dev/fd/ does not exist, it will use a
> named pipe in /var/tmp.  On a hypothetical system where neither one is
> available (Microsoft Windows?), I believe it may use a temp file.  That
> decision is made at bash's compile time.
> 
> The semantics of /dev/fd/* and named pipes are not quite identical, so
> if you're relying on some very *special* mechanisms, then there could
> indeed be portability issues.  For most scripts, however, it shouldn't
> matter.

Oh, the other thing I forgot to mention is that the semantics of /dev/fd/*
differ between Linux and BSD.  I don't have a reference available off
the top of my head, but at some time in the past few years, it came up
on one of the bug-bash or help-bash mailing lists -- someone's script
acted differently on BSD than it did on Linux because of the different
implementation of /dev/fd/ as used by a process substitution.

People do *weird* shit with bash.  The really surprising part is that
they don't *think* it's weird.

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Re: foo | tee /dev/stderr | bar  # << thanks! Greg Wooledge <wooledg@eeg.ccf.org> - 2020-07-07 07:47 -0400

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