Assigning variable value in right behalf of pipeline has no effect
Hi, bash developers!
I've noticed strange bash behaviour. If I assign variable value in
right behalf of pipeline it has no effect. Just try to execute:
XXX=10; { XXX=20; } | read; echo $XXX
XXX=10; { XXX=20; }; echo $XXX
I suppose both of them should output '20' but the first one outputs
'10'. Is it feature of bug?
This behaviour is the same for at least following bash versions: 2.05,
3.0.16 and the recent 3.2.
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Re: Assigning variable value in right behalf of pipeline has no effect
[EMAIL PROTECTED] wrote:
> XXX=10; { XXX=20; } | read; echo $XXX
>
> XXX=10; { XXX=20; }; echo $XXX
>
> I suppose both of them should output '20' but the first one outputs
> '10'. Is it feature of bug?
This is normal. It's explained in entry E4 in the bash FAQ.
paul
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Re: Assigning variable value in right behalf of pipeline has no effect
> XXX=10; { XXX=20; } | read; echo $XXX
>
> XXX=10; { XXX=20; }; echo $XXX
>
> I suppose both of them should output '20' but the first one outputs
> '10'. Is it feature of bug?
This is normal. It's explained in entry E4 in the bash FAQ.
Oh, sorry, I made a mistake in the subject, it should have been "left
half" of pipeline. Anyway the examples were right and I have already
read E4 entry of the FAQ but I still couldn't understand the results.
It's clear that 'read' is executed as an separate process and its
result (REPLY variable value) is lost but 'XXX=20' command is done by
the same process as 'XXX=10'. And if it's so why the 'XXX=20' command
has no effect in the first example? Only because it's done as part of
the pipeline?
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Re: Assigning variable value in right behalf of pipeline has no effect
[EMAIL PROTECTED] wrote:
>> > XXX=10; { XXX=20; } | read; echo $XXX
>
> It's clear that 'read' is executed as an separate process and its
> result (REPLY variable value) is lost but 'XXX=20' command is done by
> the same process as 'XXX=10'.
No, every element of a pipeline is executed in its own process. So
the only commands that are executed in the main shell process are
"XXX=10" and "echo $XXX".
paul
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Re: Assigning variable value in right behalf of pipeline has no effect
That's sad. Thank you anyway. ___ Bug-bash mailing list Bug-bash@gnu.org http://lists.gnu.org/mailman/listinfo/bug-bash
