Hi all,

I've run into a problem regarding pipes in bash, in a command that
loops. I've reduced it to a very small one-liner that fails. The two
versions below should, I'm sure, give the same output - but they
don't. I know the command is silly and useless as it is shown here,
but it's what I'm left with from something more complex after removing
as much of the complexity as I could while retaining the actual
problem I'm fighting.

ONE - this works as expected
$ for j in 1 2;do echo $j $(echo hello);done
1 hello
2 hello

TWO - this fails, apparently (warning: my guess) at the pipe
$ for j in 1 2;do echo $j $(echo hello | cat);done
1
2

THREE - To make it that bit more obscure, the following command also
works as it should, which by now I did not expect:
$ echo hello $(echo world | cat)
hello world

If 'cat' (in TWO) is replaced by 'od -a', then od does not generate
any output (at all) either. Can someone tell me what's wrong either in
what happens or in my expectation?

I have found someone on stackexchange who may, I think, be related
(https://unix.stackexchange.com/questions/364765/store-command-output-in-variable-when-command-includes-pipes)
but unfortunately that was not resolved. I tried it with virusscanning
switched off - no difference.

Thanks for looking!

Wouter van Doorn