[Help-bash] Why BASH_SUBSHELL behaves differently in () and <()?

[Peng Yu]

Hi,

The following code shows that BASH_SUBSHELL behaves differently in ()
and <(). But my understanding is that, in both case, the echo commands
are run in a subshell. Is it so? If so, 1 instead of 0 should be
printed in the last command?

~$ cat main.sh
#!/usr/bin/env bash

echo xxx "$BASH_SUBSHELL"
(
echo yyy "$BASH_SUBSHELL"
)

cat <(echo zzz "$BASH_SUBSHELL" >&2)
~$ ./main.sh
xxx 0
yyy 1
zzz 0

-- 
Regards,
Peng