[Techtalk] weirdness piping to a variable

[Miriam English]

Hi folks,

I was writing a little script today to automate something I was doing by 
hand a lot. During the writing I needed to assign the result of a 
sequence of piped commands to a variable. Normally I'd give the variable 
name and assign it to the piped sequence of commands in backticks, but 
that's always felt clumsy to me, especially if the chain of piped 
commands was long. I occurred to me that it would be clearer if I could 
take the output of a lot of commands I'd piped together and then pipe 
the result into a variable. I couldn't think of a way to do this so 
looked online and found something like this:

echo "quick brown fox" | cut -d' ' -f2 | ( read a ; echo $a )

It works, but it appears that I can only use "read" inside the 
parenthesised part. I have no idea why. If I try to do it without the 
parentheses like this:

echo "quick brown fox" | cut -d' ' -f2 |  read a ; echo $a

nothing happens. I don't understand why.

As I understand it, the part inside parentheses is another process. I 
can get variables into it, but unfortunately not out.

a="one" ; echo "two" | (read b ; echo "$a and $b") ; echo "$a and $b."

It's nice to be able to pipe values into a variable because it maintains 
the left to right conceptual flow and makes it easier for me to 
understand what I was doing when I come back much later, but it isn't 
much help if I can't use the variables outside the parentheses.

Anybody have any ideas?

Cheers,

	- Miriam

-- 
If you don't have any failures then you're not trying hard enough.
  - Dr. Charles Elachi, director of NASA's Jet Propulsion Laboratory
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