How awk passes a value to the shell

Today, writing scripts, encountering awk script to the shell of the case, the internet Google, found that there are some problems, through the pipeline, through Eval, feeling is very complex. So I thought to try it with read.

First, a test file Test.txt is constructed, and the contents are 1 2 3.

First try

' {print $ $} ' test.txt | Read a b C

But echo $a, found to be empty, failed.

Try it.

" 1 2 3 " | Read a b C

You can't assign a b c to a value.

It seems that read is not the use of, angry Google, in StackOverflow found a similar problem (StackOverflow true artifact Ah! ）

Links: http://stackoverflow.com/questions/374687/why-is-echo-foo-read-a-echo-a-not-working-as-expected

There was a reply from the Lord mentioning that

Read a < < (echo foo)

You can assign a value to a, try it, sure enough.

And then try

Read a B c< < (echo foo goo hoo)

You can also assign a B c to a value separately! It's so exciting!

Then try

' {print $ $} ' test.txt)

Failed, the value of a becomes 123,b,c empty.

Why is this? Because awk does not print a space, it only prints 123, which of course is assigned to a.

So, add separators

' {print $ "" $ "" $ $} " ' test.txt)

It's a success!

Considering my awk is going to be a little more complicated.

1 ' {test=$1;test2=$2;test3=$3}end{print Test,test2,test3} ')

And it worked!

Thus, awk can pass values to the shell in such a way.

How awk passes a value to the shell