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Re: [Help-bash] silly question - which is better to pipe 2 sources into
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From: |
Greg Wooledge |
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Subject: |
Re: [Help-bash] silly question - which is better to pipe 2 sources into one command |
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Date: |
Mon, 30 Apr 2018 10:22:21 -0400 |
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User-agent: |
NeoMutt/20170113 (1.7.2) |
On Mon, Apr 30, 2018 at 09:10:41AM -0500, John McKown wrote:
> Way one: { pgm1; pgm2; } | pgm3
> Way two: cat <(pgm1) <(pgm2) | pgm3
>
> Way one _seems_ better to me mainly because there are fewer processes
> running.
Agreed. That is what I'd use.
> But I'm wondering a bit about way two. I don't know really how that is
> working. I think that "pgm1" and "pgm2" are both fork()'d & exec()'d to run
> concurrently.
But cat reads all of the first input (until EOF), before starting to read
the second input. So the second process is simply blocked until cat is
ready to read from it.
It's still the more complex (therefore worse) choice.